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Record
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ID Methods Electrophysiology
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Methods Electrophysiology.ID Ref.
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Neurons.ID Ref.
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-1725086893
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-1725086893
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988800474
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I(cat)
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Cations
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-
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-
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-
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-35 mV
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-
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-
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-
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Fig. 1B
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p.2126
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-
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988800474
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-1725086893
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-1725086893
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-1725086893
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988800474
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I(NaP)
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Na+
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-
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60-3160 pA (median 308 pA)
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-
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-60 mV
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-
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-25 - -20 mV
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-
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Fig. 1-3
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pp.2126-2129
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Data on time and voltage-dependence of inactivation, responses to conditioning pulses and pulse-train stimulation.
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988800474
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-1725086893
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-1041488843
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-1041488843
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996239748
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CaP
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Ca2+
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-
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-
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-
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-
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-
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-
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"The P-current is the dominant high threshold voltage-activated (HVA) current in cerebellar Purkinje neurones (Llinas, Sugimori, Hillman & Cherksey, 1992). It is activated over the same range of membrane potentials as the two other HVA current components and cannot be distinguished by its kinetics, and single channel recordings have revealed unitary conductance levels in the same range as for L- and N-channels (Usowicz, Sugimori, Cherksey & Llinas, 1992). Consequently, evidence for the presence of P-channels has relied on pharmocological tests."p.197
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-
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-
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Blocked specifically by omega-Aga-IVA. Partially supressed by nifedipine. Constitutes ~30% of HVA.
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996239748
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-1041488843
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-1041488843
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-1041488843
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996239748
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HVA-Ca
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Ca2+
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-
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-
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-
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-
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-
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-
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"About 11-12% of the HVA current was insensitive to the saturating concentrations of three organic blocking agents (omega-Aga-IVA, omega-CgTX and nifedipine). This insensitive component may be due to incomplete inhibition by one or all of these blocking agents, or it may be due to a separate unclassified set of calcium channels."p.204
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-
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p.204
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The fourth HVA component was blocked by Cd-ions.
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996239748
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-1041488843
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-1041488843
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-1041488843
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996239748
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L-current
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Ca2+
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-
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-
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-
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-
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-
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-
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"Nevertheless, the results of our experiments in which nifedipine was applied after the application of both omega-Aga-IVA and omega-CgTX, suggest that about 30% of the HVA current in neocortical neurones are dihydropyridine sensitive (presumed L-channels)."p.203
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-
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-
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Nifedipine is nonspecific blocker of L-channels.
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996239748
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-1041488843
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-1041488843
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-1041488843
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996239748
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N-current
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Ca2+
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-
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-
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-
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-
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-
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-
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"In the present study omega-CgTX blocked about 26% of the HVA current, which is comparable to the percentages found previously in these cells (20%, Sayer et al. 1990, 30%, Brown et al. 1993)."p.203
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-
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p.203
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N-current is specifically blocked by omega-CgTX.
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996239748
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-1041488843
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-944650159
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-944650159
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1004695855
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I(Ca)
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Ca2+
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-
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-
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-
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-
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-
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-
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"Plateaus could also be evoked by focal glutamate iontophoresis on basal dendrites (Oakley et al. 2001). In the present study, the spatial extent of these plateaus were examined on two cells. Figure 6 shows the results obtained in one of these cells. Focal glutamate iontophoresis at a site 128 µm from the soma on a basal dendrite evoked an all-(red trace, bottom)-or-none (gray trace, bottom) plateau. The corresponding pseudocolor plot (Fog. 6, top) shows that the plateau was restricted to a small region surrounding the iontophoretic site (indicated by dashed line in pseudocolor plot). A 50% contour drawn around the region estimates the proximal extent of the plateau as 16 µm and the distal extent as 15 µm. In this cell, the spatial extent of the plateau was no significantly changed when 100 µm AP-5 was added to the bath and the experiment was repeated (data not shown). In the second cell tested, iontophoresis at a site 105 µm from the soma evoked a plateau, which was estimated to extend 20 µm proximally and 10 µm distally."p.510
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Fig. 6
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p.510
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-
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1004695855
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-944650159
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-866037043
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-866037043
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999521822
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Ca
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Ca2+
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-
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-
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-
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-
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-
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-
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"There were no distinctive features of the Ca2+ currents in the two nonpyramidal (bipolar) neocortical neurons. Both had high- and low-threshold components, and the I-V relations had thresholds and maxima within the range of values for pyramidal neurons.".pp.1599-1600
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-
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pp.1599-1600
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-
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999521822
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-866037043
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-806603121
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-806603121
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974817158
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High-threshold Ca
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Ca2+
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-
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264+-116 pA
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-
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-45 mV
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-
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-20 - -10 mV
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"These currents were shown to be calcium fluxes by their proportionate reduction in lowered external calcium (0.1 mM, n=2) and their blockade in 0.4 mM cadmium (n=6). An outward current seen at positive voltage commands was probably carried by cations passing outward through the calcium channel [8,9] and was absent when N-methyl-D-glucamine was substituted for Tris in the electrode solution (n=2)."p.176.
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Fig.1
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p.176
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-
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974817158
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-806603121
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-806603121
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-806603121
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974817158
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Low-threshold Ca
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Ca2+
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-
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75+-32 pA
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-
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-65 mV
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-
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-30 mV
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"These currents were shown to be calcium fluxes by their proportionate reduction in lowered external calcium (0.1 mM, n=2) and their blockade in 0.4 mM cadmium (n=6). An outward current seen at positive voltage commands was probably carried by cations passing outward through the calcium channel [8,9] and was absent when N-methyl-D-glucamine was substituted for Tris in the electrode solution (n=2)."p.176.
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Fig.1
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p.176
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-
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974817158
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-806603121
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-806603121
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-806603121
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974903425
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High-threshold calcium
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Ca2+
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-
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-
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-
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-
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-
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-
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"Table I lists the responses of currents to application of divalent ions and organic compounds. The high-threshold currents were more sensitive than the low-threshold currents to block by Cd2+, while the reverse was true for Ni2+. Replacement of external Ca2+ by Ba2+ incresed the maximum high-threshold current and shifted it it approximately 10 mV to the left on the I-V curve. The low-threshold current was reduced in Ba2+. Nimodipine (Sigma) supressed both the low-threshold and the high-threshold currents (Fig.2A). Racemic BAY K 8644 (Miles Labs.) had an agonist effect which was most pronounced at command potentials negative to the maximum of the I-V curve (e.g. Fig. 2B). The increase at the point of maximum inward current was smaller and more variable (mean 16%), and the current was reduced at positive potentials. There was no consistent effect on the low-threshold current. Omega-Conotoxin GVIA (Peninsula Labs.) reduced the high-threshold current only (Fig. 2C). Nimodipine and omega-conotoxin attenuated the currents without any voltage shift in the I-V curves. The effects of all substances were reversed by washing, except for omega-conotoxin, from which there was only a slight recovery".pp.176-177.
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Table 1, Fig.2
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p.177
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No attempt to separate into subcomponents of Ca-conductances.
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974903425
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-806603121
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-806603121
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-806603121
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974903425
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Low-threshold Ca
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Ca2+
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-
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-
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-
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-
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-
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-
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"Table I lists the responses of currents to application of divalent ions and organic compounds. The high-threshold currents were more sensitive than the low-threshold currents to block by Cd2+, while the reverse was true for Ni2+. Replacement of external Ca2+ by Ba2+ incresed the maximum high-threshold current and shifted it it approximately 10 mV to the left on the I-V curve. The low-threshold current was reduced in Ba2+. Nimodipine (Sigma) supressed both the low-threshold and the high-threshold currents (Fig.2A). Racemic BAY K 8644 (Miles Labs.) had an agonist effect which was most pronounced at command potentials negative to the maximum of the I-V curve (e.g. Fig. 2B). The increase at the point of maximum inward current was smaller and more variable (mean 16%), and the current was reduced at positive potentials. There was no consistent effect on the low-threshold current. Omega-Conotoxin GVIA (Peninsula Labs.) reduced the high-threshold current only (Fig. 2C). Nimodipine and omega-conotoxin attenuated the currents without any voltage shift in the I-V curves. The effects of all substances were reversed by washing, except for omega-conotoxin, from which there was only a slight recovery".pp.176-177.
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Table 1, Fig. 2
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p.177
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Authors claim similarity to T-current (p.177).
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974903425
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-806603121
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-781327707
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-781327707
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986573713
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I(h)
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Cations
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-
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-
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-
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-
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-
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-
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"..., whereas in patches from apical dendrites the magnitude of this slow inward current increased as recordings were made more distally from the soma (slope of linear regression 9 pA/100 µm; Fig. 1B)."
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Fig.1B.
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p.3178
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-
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986573713
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-781327707
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-625879160
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-625879160
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1006622979
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I(A)
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K+
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-
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-
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about -66 mV
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-
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-
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-
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"Two general classes of outward current were seen in cell-attached patches, as in nucleated patches. A fast transient current resembled I(A) (Fig. 1A). This current, when present in a cell-attached patch, was very consistent in all its properties (below)."p.612
"In some patches, particularly those containing many channels, a mixture of I(A) and I(K) was seen (Fig. 1D). The same kinetic diversity was also apparent in outside-out patches (not illustrated)."p.613
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Fig. 1
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pp.612-613
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-
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1006622979
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-625879160
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-625879160
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-625879160
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1006622979
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I(K)
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K+
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-
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-
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-82+-6 mV
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-
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-
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-
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"Two general classes of outward current were seen in cell-attached patches, as in nucleated patches. ... A slow transient or plateau current was also observed, which may correspond to I(K) (Fig. 1B and C). Surprisingly, however, the I(K)-like current was variable in its inactivation behaviour: in some cell-attached patches it inactivated like I(K) in nucleated patches (Fig. 1C); in other patches it did not inactivate at all during a 500 ms test pulse (Fig. 1B). In some patches, particularly those containing many channels, a mixture of I(A) and I(K) was seen (Fig. 1D). The same kinetic diversity was also apparent in outside-out patches (not illustrated)."pp.612-613
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Fig. 1
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pp.612-613
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-
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1006622979
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-625879160
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-381558745
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-381558745
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986573713
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I(h)
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Cations
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-
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-
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-7.94+-0.77 mV
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-70.0 mV
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-92 mV
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-110 mV
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-
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Fig.1
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pp.3178-79
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Also values on steepness coefficients, activation/deactivation timeconstants
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986573713
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-381558745
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-342234224
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-342234224
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-1051416814
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I(Ca)
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Ca2+
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-
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-
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-
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-
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-
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-
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"To verify directly that increases in dendritic [Ca2+]i result from Ca2+ influx through voltage-gated Ca2+ channels, iontophoretically evoked changes in dendritic [Ca2+]i were compared before and after the addition of the Ca2+ channel blocker Cd2+ in three cells. Typical results are shown in Fig. 5. The iontophoretic current that evoked the plateau and rise of [Ca2+]i shown in Fig. 5A evoked only a passive membrane potential response and little or no increase in [Ca2+]i in the presence of 200 µM Cd2+ (Fig. 5B). In this and each cell tested, a subthreshold iontophoresis also evoked a significant rise of [Ca2+]i that was also blocked by Cd2+ (data not shown]."pp.509-510
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Fig. 5
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pp.509-510
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-
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-1051416814
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-342234224
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-342234224
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-342234224
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1004695855
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I(Ca)
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Ca2+
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-
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-
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-
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-
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-
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-
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"From the pseudocolor plot, it can be seen that the largest rise in [Ca2+]i occured at the iontophoretic site (indicated by dashed line on pseudocolor plot). During the initial Ca2+ and Na+ spikes, [Ca2+]i increased above resting levels at locations both proximal and distal to the iontophoretic site. Following these initial spikes, [Ca2+]i decayed to the resting level at these proximal and distal locations, whereas [Ca2+]i remained above the resting level near the iontophoresis site for the remainder of the iontophoresis. After the iontophoresis was terminated, [Ca2+]i decayed to baseline. In this and all cells examined, an iontophoresis that was subthreshold for either the plateau or the initial transient Ca2+ spike caused an increase of [Ca2+]i, and the largest rise in [Ca2+]i ocurred near the iontophoretic site. In Fig. 2C, the plateau was evoked (red trace at bottom) during a larger [-70 nA) iontophoresis at the same site. As indicated by the pseudocolor plot (Fig. 2C, top), during and immediately after the initial Ca2+ and Na+ spike the spatial-temporal increase of [Ca2+]i was similar to that of Fig. 2B. Subsequently, when the plateau was evoked, the increase of [Ca2+]i at the iontophoretic site was larger than during the subthreshold response of Fig. 2B or the subthreshold portion of the response that preceeded the plateau in Fig. 2C. In addition, [Ca2+i] rose above its rest value both proximal and distal to the iontophoretic site following plateau initiation, and this rise persisted for the duration of the plateau. Thus the plateau was associated with a [Ca2+]i rise that differed from a subtreshold response in both magnitude and spatial extent. Our primary finding is that the rise of [Ca2+]i associated with plateau generation declined with distance from the iontophoretic spike, both proximally and distally. This same pattern, highest around the iontophoretic site and lower at the proximal and distal boundaries of the imaged region, was evoked during plateau generation in all recorded cells. Assuming for the moment that the rise of [Ca2+]i is caused entirely by Ca2+ influx through voltage-gated channels, these results imply that dendritic membrane potential (i.e., plateau amplitude) also declined with distance. That is, the plateau propagates decrementally both proximal and distal to its site of initiation. In contrast, a regenerative response that propagated actively with constant amplitude, like a Na+ spike propagating down the axon, would be expected to result in a similar rise of [Ca2+]i along the whole region of active propagation. The assumptions on which this conclusion is based were tested in experiments described in the following text."p.507
"Based on the observations and rationale described in the preceeding text, the proximal and distal extent of the active plateau-generating region was defined as the most proximal an distal extent of the 50%-of-peak contour line during a plateau. Using this criterion, the active plateau-generating region was remarkably small but of similar magnitude among the cells tested. Active plateau initiation extended 50 µm proximally and 38 µm distally from the iontophoretic site in the experiment in Fig. 2C. Plateaus were evoked on the apical dendrite of 12 cells bathed in physiological saline. Data from these 12 plateaus are plotted as squares in Fig. 4. ... In these experiments, the proximal extent of active initiation ranged from 20 to 113 µm (mean: 63.2 µm), and the distal extent ranged from 10 to 207 µm (mean: 51.4 µm). The proximal and distant extents were not significantly different (P = 0.47, paired, 2-tailed, Students t-test). The plot of Fig. 4 also shows that the plateaus were evoked over the whole extent of the apical dendrite examined (from 178 to 648 µm from the soma), and all plateaus were centered spatially on about the iontophoretic site. The ability to evoke plateaus at sited over this length of the apical dendrite indicates that Ca2+ channel density is adequate for plateau generation over (at least) this length of the apical dendrite."p.508
""Since the peak rise of [Ca2+]i always ocurred around the iotophoretic site at all locations tested (from 178 to 648 µm on the apical dendrite; cf. Fig. 4), it is unlikely that the plateaus were initiated at discrete "hot spots" on the dendrite. These results strongly suggest that CDRPs can be initiated at any point on the main apical trunk where the membrane potential reaches plateau threshold."p.510
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Fig. 2, 3, 4
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pp.506-508, 510
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No Ca2+ channel "hotspots", - uniform distribution.
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1004695855
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-342234224
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-342234224
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-342234224
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1023579893
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I(Ca)
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Ca2+
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-
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-
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-
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-
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-
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-
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"To confirm that Ca2+ influx through NMDA channels was not a major influence on the measured rise in [Ca2+]i and to additionally test whether the voltage-gated Na+ channel activity might influence the initiation site or spatial extent of the plateau, plateaus were evoked in an additional 10 cells bathed in 100 µM AP-5 plus 1 µM TTX. Figure 5 illustrates typical results when both Na+ channels and NMDA receptors were blocked. Plateaus were evoked in each cell tested under these conditions, and the spatio-temporal pattern of the rise of [Ca2+]i and the spatial extent of these plateaus were similar to those obtained in physiological saline. In these experiments, the estimated proximal extent of the plateaus ranged from 15 to 88 µm (mean: 53.1 µm) and the distal extent ranged from 22 to 146 µm (mean: 49.5 µm). These values were not significantly different from those obtained in physiological saline (for proximal extent P = 0.46; for distal extent P = 0.94; 2-tailed Student's t-test). As found for physiological saline, the proximal extent of plateaus evoked in AP-5 plus TTX was not significantly different from teh distal extent (P = 0.81, 2-tailed Students t-test). Data obtained from plateaus evoked in AP-5 plus TTX are plotted as triangles in Fig. 4 for comparison with plateaus evoked in physiological saline."p.509
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Fig. 4, 5
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p.509-510
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-
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1023579893
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-342234224
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-51689092
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-51689092
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999521822
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CaT
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Ca2+
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-
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47+-31 pA
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-
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~ -60 mV
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-
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~ -30 mV
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"When the depolarizing commands were preceeded by an 800 ms hyperpolarizing prepulse to -100 mV, there was an additional transient component of inward current, with a threshold for activation at about -60 mV (low-threshold or T-type Ca2+ current). The I-V relation for this current (the difference between the records with and without the prepulse) is plotted as open circles for the example cell in Fig. 2B. The maximum low-threshold current was evoked at about -30 mV and was 47+-31 pA (n = 30; excludes 2 cells in which the current was absent or unmeasurably small, and one in which the leak subtraction was unsatisfactory)."p.1598
"Steady-state inactivation of the low-threshold Ca2+ current was examined in four neurons by stepping to a constant test voltage from various prepulse potentials (each 800 ms duration). Figure 3A shows the inactivation curve based on data from four cells and example records from one cell. In each neuron the maximum current was normalized to 1.0 (i.e., inactivation fully removed), and the data points were then averaged across cells. A Boltzmann curve was fitted by an algorithm that minimized the sum of squared errors. The slope factor for the fitted curve was 5.4 mV per e-fold change. The low-threshold current was almost fully inactivated at -70 mV; inactivation was half removed at -86 mV and fully removed at about -110 mV."p.1599
"The time course for removal of inactivation of the low-threshold current was investigated in two neurons. The results from one are shown in Fig. 3B. The low-threshold current was evoked after hyperpolarizing prepulses of constant amplitude [to -95 mV in one cell (Fig. 3B) and -110 mV in the other]. In both cases removal of inactivation occured over hundreds of milliseconds and appeared almost complete by 800 ms (these cells became progressively leaky when the durations of hyperpolarizations exceeded 1 s, so longer prepulses were not examined). These findings indicate that both strong (more negative than -100 mV) and prolonged (hundreds of ms) hyperpolarization is required for inactivation of the low-threshold current to be fully removed."p.1599
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Fig. 2, 3
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pp.1598-1599
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-
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999521822
|
-51689092
|
|
-51689092
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-51689092
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999521822
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HVA-Ca
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Ca2+
|
-
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428+-233 pA
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>+40 mV
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~-45 mV
|
-
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-10 - -20 mV
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"From the holding potential of -60 mV, depolarizing current commands evoked a slowly inactivating inward current, with a threshold at about -45 mV and a maximum between -10 and -20 mV (high-threshold current; Fig.2, [filled triangles]). The peak current at the maximum of the I-V was 428+-233 pA for the pyramidal neurons (n = 33). The currents usually reversed positive to about +40 mV in the Tris-PO4 internal solution (and at more positive potentials with the N-methyl-D-glucamine internal solution), probably due to the outflow of internal cations. The rate of inactivation was variable between cells, and no attempt was made to quantify it in the experimental situation with artificial internal Ca2+ buffering."p.1598
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Fig. 2
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p.1598
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-
|
999521822
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-51689092
|
|
-51689092
|
-51689092
|
1841045319
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CaL
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
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"Nifedipine (10 µM) inhibited 48 +-16% of the control amplitude of the high-threshold current (n = 6; this includes one nonpyramidal neuron in which the current suppresion was 57%). In three cells tested with 10 µM nimopidine the Ca2+ current reduction was 43 +- 7.2%. The effects of nifepidine and nimopidine were reversible."p.1600
"Single-channel studies in other mammalian neurons have attributed ... the dihydropyridine-sensitive component to L-type channels (Hess 1990), although concentrations of dihydropyridine Ca2+ antagonists that fully-inhibit L-type current may weakly suppress other current components as well (Regan et al. 1991)."p.1603
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Fig.4, 5
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p.1600, 1603
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-
|
1841045319
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-51689092
|
|
-51689092
|
-51689092
|
1841045319
|
CaN
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
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"In four cells, omega-CgTX (16 µM) reduced the peak Ca2+ current by 21 +- 5.1% with only slight recovery on washing."p.1600
"Single channel studies in other mammalian neurons have attributed the omega-CgTX-sensitive component to N-type channels..."p.1603
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Fig. 4
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p.1600, 1603
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-
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1841045319
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-51689092
|
|
-9806123
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-9806123
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-232296371
|
I(Na)
|
Na+
|
-
|
-
|
-
|
-
|
-
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-
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"Fig. 3B, location 1 shows Na+ channel currents (single traces and the ensemble average) activated by voltage commands in a somatic patch, and Fig. 3B, location 2 shows comparable recordings from a dendritic patch about 80 µm away (see locations 1 and 2 in Fig. 3A). Fig. 3B, locations 3 and show recordings from 2 additional sites [located at the junction of soma and apical dendrite (location 3 if Fig. 3 A and B) and further distal on the dendrite (location 4 in Fig. 3 A and B)] from the same neuron. Note that although there was Na+ channel activity at each location, the density of channels was not precisely equivalent at all locations. For example, the dendritic location in Fig. 3A, location 4 had an unusually high level of Na+ current; this would be indicative of a " hot spot" (16, 17). All recordings showed transient (about 1 msec) inward openings that were activated in a similar pattern by each voltage command at a given site (compare sequential sweeps in each vertical column of Fig.3B)."
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Fig.3
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pp.2475-2476
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-
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-232296371
|
-9806123
|
|
-9806123
|
-9806123
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987614460
|
I(Na)
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Na+
|
-
|
-
|
-
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-
|
-
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-
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"The relative density of Na+ currents in proximal (som-basilar dendritic ) and distal apical dendritic was similar. Regression analysis showed that there was a significant correlation between area and Na+ current (Fig.2D and Table 1)."
"By using data obtained from differential perfusion experiments, it was also possible to determine whether there were significant differences between the properties of Na+ currents on somatic and dendritic membranes....In each case, no significant differences in theses parameters were found between somatic and dendritic membranes."
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Fig.2, Table 1.
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pp.2474-2475
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-
|
987614460
|
-9806123
|
|
5642164
|
5642164
|
986573713
|
I(h)
|
Cations
|
-
|
-
|
-
|
-
|
-
|
-
|
"...Recordings made from axonal and somatic patches revealed little or no slow inward current..."
|
Fig.1B
|
p.3178
|
|
986573713
|
5642164
|
|
35614620
|
35614620
|
-20718951
|
I(Na)
|
Na+
|
109+-39 pS/µm^2
|
-
|
-
|
-55 mV
|
-30.6+-2.8 mV
|
-
|
-
|
Table 1-2;Figs. 6-9
|
-
|
Kinetic parameters fitted; biexponential decay; ratio of slow to fast component of Na-current = 0.19+-0.030
|
-20718951
|
35614620
|
|
35614620
|
35614620
|
974208830
|
I(Na)
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"The biexponential nature of Na+ current decay was verified by recording single-channel Na+ currents from cell-attached patches. Examples of single-channel currents from a P10 neuron are shown in Fig.10B. Single-step depolarizations resulted in a barrage of early channel openings, as well as late individual events with latencies of up to tens of milliseconds. Occasionally bursts of openings were seen that lasted the duration of of the depolarization. Ensemble averages of Na+ channel currents demonstrated two decay components, with similar time constants to those obtained with whole-cell clamp currents (Fig.10B). No significant differences in the amplitudes of the early and late single-channel openings could be detected."pp.790-791.
|
Fig.10
|
pp.790-791
|
-
|
974208830
|
35614620
|
|
216257617
|
216257617
|
-862865877
|
I(A)
|
K+
|
-
|
-
|
-
|
-
|
-31 mV
|
-
|
-
|
Fig.5
|
pp.55-57
|
Data from P1 rat. Also data on half-inactivation.
|
-862865877
|
216257617
|
|
216257617
|
216257617
|
-862865877
|
I(K)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"...with external and internal solutions (see Table 1) that minimized the contribution of Ca2+-activated K+-currents, which are not studied here."
"The differences (see legend, Fig. 5A) between the transient and sustained current are essentially similar to differences reported previously for the A current and the delayed rectifier, with the A current showing activation and steady state inactivation at relatively less depolarized potentials and the delayed K current showing only incomplete inactivation at positive voltages (Adams et al., 1980; Adams and Galvan, 1984)."
|
Fig.4
|
pp.55-57
|
Currents in response to voltage steps, normalized current densities (early and late component) in Fig. 4.
|
-862865877
|
216257617
|
|
216257617
|
216257617
|
-862865877
|
I(Kdr)
|
K+
|
-
|
-
|
-
|
-
|
10 mV
|
-
|
-
|
Fig. 5
|
pp.55-57
|
Data from P1 rat. Also data on half-inactivation.
|
-862865877
|
216257617
|
|
216257617
|
216257617
|
-754473072
|
I(CaL)
|
Ca2+
|
40 pS/µm^2
|
-
|
-
|
-
|
-10 mV
|
-
|
-
|
Fig.6, 7
|
pp.57-59
|
Data from P11 rat. Plots of response to voltagesteps, I-V curves, fits.
|
-754473072
|
216257617
|
|
216257617
|
216257617
|
-754473072
|
I(CaT)
|
Ca2+
|
20 pS/µm^2
|
-
|
-
|
-
|
-70 mV
|
-
|
-
|
Fig.6, 7
|
pp.57-59
|
Data from P11 rat. Plots of response to voltagesteps, I-V curves, fits.
|
-754473072
|
216257617
|
|
216257617
|
216257617
|
1693123346
|
I(Na)
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"However, there is a developmental change in activation in inactivation kinetics that is evident in both cell types (Huguenard et. Al., 1988). This is indicated by the residual Na+ current that remains at the end of the 15-ms current pulse in the P55 neuron but which is absent in the E18 neuron (i.e. compare current levels at the arrows in Fig. 3A)."
"By contrast, in the mature neuron, complete decay took approximately 10 times longer and was best fitted with 2 exponentials with fast (3-1 msec) and slow (30-10 msec) time constants."
|
Fig.3
|
pp.52-55
|
Responses to voltage steps, normalized conductance densities, steady state inactivation and peak activation curves and recovery time course plots in Fig.3.
|
1693123346
|
216257617
|
|
406866101
|
406866101
|
-1756532732
|
INa
|
Na+
|
-
|
-
|
22.2+-2.7 mV
|
~ -65 mV
|
-44.8+-1.9 mV
|
-
|
"After papain produced its full effectr, INa became larger at negative potentials (Figs. 1A, and 2, A and B) and was evoked by depolarizations that evoked no transient current in control records (starting at about -65 mV for the cell of Fig. 1A). Papain resulted in a leftward shift of the activation curve by 7.2 mV in this cell (Fig. 1B). A similar leftward shift (averaging 6.4 mV; see Table 1) was seen in each of the seven cells tested. Peak INa became 32% larger on average, but there was no significant change in ENa, Gmax or the slope of the activation curve (see Table 1). Figure 2, A and B shows how papain modified the time-course of INa during small and large depolarizations. INa persisted throughout either depolarization with little decrement from its peak value. During either depolarization the initial rate of rise of INa was unchanged, but the time to reach peak current was much greater for the small depolarization (Fig. 2A) than for the large depolarization (Fig. 2B)."p.2564
|
Fig. 2, Table 1
|
p.2564
|
Papain removes the inactivation of fast sodium channels.
|
-1756532732
|
406866101
|
|
406866101
|
406866101
|
-850117393
|
INa
|
Na+
|
-
|
-
|
25.1+-1.6 mV
|
~ -55 mV
|
-43.5+-1.1 mV
|
~ -30 mV
|
"INa was first detected near -55 mV and peaked near -30 mV. ... In five experiments the activation of INa and INaP were compared in the same cell. In each cell INaP was first detected at potentials 5-12 mV more negative than for INa (mean values: -65.2 mV for INaP; -56.6 mV for INa)."p.2564
|
Fig. 1, Table 1
|
pp.2563-2564
|
I-V relationships and activation curves in Fig. 1.
|
-850117393
|
406866101
|
|
406866101
|
406866101
|
1000211302
|
INaP
|
Na+
|
-
|
-
|
-
|
~ -65 mV
|
-50.4+-1.4 mV
|
~ 40 mV
|
"INaP both activated and peaked at more negative potentials (near -65 and -40 mV, respectively) than INa. In five experiments the activation of INa and INaP were compared in the same cell. In each cell INaP was first detected at potentials 5-12 mV more negative than for INa (mean values: -65.2 mV for INaP; -56.6 mV for INa)."p.2564
|
Fig. 1, Table 1
|
pp.2563-2564
|
I-V relationships and activation curves in Fig. 1.
|
1000211302
|
406866101
|
|
481039627
|
481039627
|
-1020917390
|
I(NaP)
|
Na+
|
-
|
(Fig. 2)
|
-
|
about -60 mV
|
-
|
-40 to - 35 mV
|
"As has also been found for the fast INa during development (Huguenard et al. 1988), the voltage dependence of INaP activation did not change during the time frame of out study. However, INaP seemed to increase in magnitude during development (Fig. 1A)."
"As shown in the histogram of Fig. 2A, the strongest increase in INaP amplitude ocurred between aoung and juvenile rats where the mean peak INaP amplitude more than doubled, whereas a smaller increase was seen from juvenile to mature rats."
"Surprisingly, only a rather weak correlation (r=0.61)was found between age amd maximal current density."
|
Fig. 1, 2.
|
pp.291-292
|
Persistent sodium current was completely blocked by TTX.
|
-1020917390
|
481039627
|
|
987005279
|
987005279
|
986573713
|
I(h)
|
Cations
|
-
|
-
|
-
|
-
|
-
|
-
|
"...Recordings made from axonal and somatic sites revealed little or no slow inward current..."
|
Fig.1B
|
p.3178
|
-
|
986573713
|
987005279
|
|
987681444
|
987681444
|
987614460
|
I(Na)
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"The relative density of Na+ currents in proximal (som-basilar dendritic ) and distal apical dendritic was similar. Regression analysis showed that there was a significant correlation between area and Na+ current (Fig.2D and Table 1)."
"By using data obtained from differential perfusion experiments, it was also possible to determine whether there were significant differences between the properties of Na+ currents on somatic and dendritic membranes....In each case, no significant differences in theses parameters were found between somatic and dendritic membranes."
|
Fig.2, Table 1.
|
pp.2474-2475
|
-
|
987614460
|
987681444
|
|
987766595
|
987766595
|
-192623055
|
I(NaP)
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Apparently, the continous Na+ influx associated with INaP was required to cause a detectable rise of [Na+]i."
"In each neuron tested, INaP-associated reductions of fluorescence in the apical dendrites were detecable as far as the dye could be visualized (distance from soma: 50-300 µm, n = 12)."
|
Fig.1, 2
|
p.1190
|
Amplitude of induced plateau depolarization (PD) during current pulse 54.2+-5.5 mV.
|
-192623055
|
987766595
|
|
988292479
|
988292479
|
-862865877
|
I(K)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"...with external and internal solutions (see Table 1) that minimized the contribution of Ca2+-activated K+-currents, which are not studied here."
"In more mature nonpyramidal cells, a transient current did not appear, but the sustained current became larger."
"The differences (see legend, Fig. 5A) between the transient and sustained current are essentially similar to differences reported previously for the A current and the delayed rectifier, with the A current showing activation and steady state inactivation at relatively less depolarized potentials and the delayed K current showing only incomplete inactivation at positive voltages (Adams et al., 1980; Adams and Galvan, 1984)."
|
Fig.4
|
pp.55-57
|
Currents in response to voltage steps, normalized current densities (early and late component) in Fig. 4.
|
-862865877
|
988292479
|
|
988292479
|
988292479
|
-754473072
|
I(CaL)
|
Ca2+
|
60 pS/µm^2
|
-
|
-
|
-
|
-10 mV
|
-
|
-
|
Fig.6, 7
|
pp.57-59
|
Data from P11 rat. Curves of response to voltage-steps, I-V curves, fits.
|
-754473072
|
988292479
|
|
988292479
|
988292479
|
-754473072
|
I(CaT)
|
Ca2+
|
5 pS/µm^2
|
-
|
-
|
-
|
-65 mV
|
-
|
-
|
Fig. 6, 7
|
pp.57-59
|
Data from P11 rat. Curves of response to voltage-steps, I-V curves, fits.
|
-754473072
|
988292479
|
|
988292479
|
988292479
|
1693123346
|
I(Na)
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"However, there is a developmental change in activation in inactivation kinetics that is evident in both cell types (Huguenard et. Al., 1988). This is indicated by the residual Na+ current that remains at the end of the 15-ms current pulse in the P55 neuron but which is absent in the E18 neuron (i.e. compare current levels at the arrows in Fig. 3A)."
"By contrast, in the mature neuron, complete decay took approximately 10 times longer and was best fitted with 2 exponentials with fast (3-1 msec) and slow (30-10 msec) time constants."
|
Fig.3
|
pp.52-55
|
Responses to voltage steps, normalized conductance densities, steady state inactivation and peak activation curves and recovery time course plots in Fig.3.
|
1693123346
|
988292479
|
|
989418859
|
989418859
|
-1662948559
|
I(Na,p)
|
Na+
|
-
|
-
|
-
|
-60 mV
|
-46.9 mV
|
-30 mV
|
-
|
Fig.1
|
p.109
|
Fit to Boltzmann.
|
-1662948559
|
989418859
|
|
989418859
|
989418859
|
-1357204228
|
I(Ca)
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
|
"The current traces and I-V relationship of the total Ca2+ currents under control conditions and during ATX II perfusion are shown in Fig.2B, which also includes a T-type current, as the recording steps were preceded by a 100 ms hyperpolarizing prepulse at -100 mV."
|
Fig.2
|
pp.109-110
|
I-V plot.
|
-1357204228
|
989418859
|
|
989418859
|
989418859
|
-1322394210
|
I(Na,f)
|
Na+
|
-
|
< 1 nA
|
-
|
-60 mV
|
-27.5 mV
|
-15 mV
|
-
|
Fig.1
|
pp.107-109
|
Also fit to Boltzmann distribution in fig.1. Inactivation parameters.
|
-1322394210
|
989418859
|
|
989418859
|
989418859
|
732686535
|
I(K)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"The current traces traces shown in the figure include Ca2+ -activated K+ currents, as the Ca2+ currents were not blocked but hidden by the outward current."
|
Fig.2
|
p.109
|
I-V plot.
|
732686535
|
989418859
|
|
999088458
|
999088458
|
-231029841
|
CaL
|
Ca2+
|
-
|
-
|
-
|
-
|
-19+-11/-17+-7 mV
|
-
|
"We operationally defined L-type current as that blocked by a saturating dose of the DHP antagonist Nif,..."p.1433
"In adult neurons, Nif (5 µM) blocked an average of 32+-15% (n = 40) of the peak whole cell calcium current (Figs. 4 and 5)."p.1433
"We found that the Nif sensitive current contributed ~30% to the whole cell calcium current."p.1438
|
Fig. 4, 5, 6, 7, 8, 9. Table 1.
|
-
|
Details on activation, deactivation and inactivation in table 1. Ba2+ used as charge-carrier in experiments.
|
-231029841
|
999088458
|
|
999088458
|
999088458
|
-231029841
|
CaN
|
Ca2+
|
-
|
-
|
-
|
-
|
-17+-8/-16+-7 mV
|
-
|
"We operationally defined...N-type current as that blocked by a saturating dose of CgTx,..."p.1433
"HVA currents in adult cells were also reduced by CgTx (Fig. 4). CgTx (1 µM) blocked 33 +- 14% (n = 22) of the whole cell current."p.1434
"In acutely isolated sensorimotor neurons, the CgTx-sensitive current contributed ~33% to the whole cell calcium current."p.1438
|
Fig. 4, 5, 6, 7, 8, 9. Table 1.
|
-
|
Details on activation, deactivation and inactivation in table 1. Ba2+ used as charge-carrier in experiments.
|
-231029841
|
999088458
|
|
999088458
|
999088458
|
-231029841
|
CaP
|
Ca2+
|
-
|
-
|
-
|
-
|
-20+-7/-15+-7 mV
|
-
|
"We operationally defined... P-type current as that blocked by a saturating dose of AgTx..."p.1433
"AgTx also reduced the HVA currents (Figs. 4 and 5); 100 nM AgTx blocked 36 +- 16% (n = 18) of the peak current."p.1434
"A third HVA current in rat neocortical neurons was isolated by its sensitivity to omega-AgTx-IVA (P-type channels). In rat sensorimotor neurons we found that AgTx blocked 36% of the peak calcium current (see also Brown et al. 1994; 33% block)."p.1438
|
Fig. 4, 5, 6, 7, 8, 9. Table 1.
|
-
|
Details on activation, deactivation and inactivation in table 1. Ba2+ used as charge-carrier in experiments.
|
-231029841
|
999088458
|
|
999088458
|
999088458
|
-231029841
|
HVA-Ca (Nif, CgTx, AgTx res)
|
Ca2+
|
-
|
-
|
-
|
-
|
-22+-6/-25+-6 mV
|
-
|
"We operationally defined ... resistant current as that current remaining in the presence of the combination of saturating doses of Nif, CgTx, and AgTx."p.1433
"An average of 80 +- 11% (n = 9) of the whole cell current was blocked when Nif, CgTx, and AgTx were applied simultaneously (Fig. 5), with ~20% of the whole cell current resistant to a combination of these blockers."p.1434
"Our data are consisten with the resistant current being at least partially due to Q-type current, although the voltage dependency of activation for the current induced in Xenopus oocytes be injection of the rbA alfa-subunit in the Sather et al. study (Sather et al. 1993) was shifted to positive voltages versus that for the L-type current (rbC alfa-subunit)."p.1440
|
Fig. 4, 5, 6, 7, 8, 9. Table 1.
|
-
|
Details on activation, deactivation and inactivation in table 1. Ba2+ used as charge-carrier in experiments.
|
-231029841
|
999088458
|
|
999088458
|
999088458
|
999005478
|
HVA-Ca
|
Ca2+
|
-
|
-
|
-
|
-45 mV
|
-17 +- 1 mV
|
-
|
"Two millimolar Ca2+ is close to the physiological concentration of extracellular Ca2+. We found that currents obtained with 5 mM Ba2+ exhibited similar voltage dependence of activation to those obtained with 2 mM Ca2+. Thus the I-V relationships obtained for 5 mM Ba2+ in this study are likely to be typical of those for Ca2+ currents under more physiological conditions."p.1433
"Our principal findings were as follows. 1) Neocortical pyramidal cells express L-, N-, and P-type calcium channels, as well as a component resistant to specific blockers of those channels. 2) There were no significant biophysical differences between physiologically defined L-, N-, and P-type current components. 3) The resistant current had a shorter time to peak activation, greater percent inactivation, more rapid inactivation kinetics, and more negative voltage dependence of activation compared with the other three types."p.1437
"These results of the present studies are limited to the soma and proximal dendritic membranes due to the dissociation procedure, and voltage-gated calcium channels appear to be differentially localized to different parts of the cell (L-type channesl primarily on soma and proximal dendrites and N- and P-type channels primarily on distal dendrites) (Ahlijanian et al. 1990; Westenbroek et al. 1990, 1992, 1993). It is therefore likely that N- and P-type currents contribute relatively more to the Ca2+ influx of the entire cell than is suggested by our data."p.1441
|
Fig. 1, 2, 3.
|
pp.1432-1433.
|
Ba2+ used in pharmacological experiments with the HVA Ca2+ currents.
|
999005478
|
999088458
|
|
1000126375
|
1000126375
|
-847634651
|
Ca
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Addition of 2-amino-5-phosphonovaleric acid (APV 50-100 µM), an antagonist of N-methyl-D-aspartate receptors (NMDARs) blocked the initiation of dendritic action potentials (Fig. 6A and B), and attenuated the peak amplitude of the associated [Ca2+]i transients (Fig. 6C and D; n=9). Initiation of both Ca2+ action potentials by distal synaptic stimulation and the associated [Ca2+)i transients were completely blocked by addition of the alfa-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 µM) to the extracellular solution (Fig. 6 B and D; n=3). CNQX also reduced the amplitude of synaptically evoked composite PSPs in dendrites and the soma (not shown)."p.611
"The dependence of local distal dendritic action potential initiation and the associated [Ca2+]i transient on activation of NMDA receptors probably resulted from the relatively slow activation and inactivation kinetics of NMDA receptors. Thus, it is possible that a train of AMPA-mediated EPSPs could also evoke Ca2+ actio potentials in distal apical dendrites."p.611
|
Fig. 6
|
p.611
|
-
|
-847634651
|
1000126375
|
|
1000126375
|
1000126375
|
-62810572
|
Na
|
Na+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Voltage-dependent Na+ channels contributed also to the initiation of the dendritic action potentials, as addition of TTX (1 µM) to the bath solution increased the threshold for action potential initiation by distal current injection. Dendritic regenerative potentials could still be initiated by distal synaptic stimulation when voltage-activated Na+ channels were blocked by dialysis od the neuron with QX-314 (Fig. 5A; 5-10 nM, n=3) or in the presence of TTX (1 µM) following distal dendritc current injection (Fig. 5B, n=3)."p.610
|
Fig. 5
|
p.610
|
-
|
-62810572
|
1000126375
|
|
1000126375
|
1000126375
|
999704296
|
Ca
|
Ca2+
|
-
|
-
|
-
|
-26.4+-1.9 mV
|
-
|
-
|
"Synaptic stimulation was made via electrodes which had their tips located either close to the distal branches (layers 1-2) or to the proximal apical dendritic branches (layers 5-6). Fluoroscence imaging indicated that stimulation of distal synapses in layers 1-2, which elicited a subtreshold PSP at the soma, could evoke a large [CA2+]i transient that peaked in the distal apical branches and gradually decreased in amplitude to undetecable levels along the main apical trunk (Fig. 2A). The distal dendritic [Ca2+]i transients (measured at a dendritic region more than 600 µm away from the soma) were significantly larger than those evoked by either synaptic stimulation of the proximal apical dendrite (100-300 µm lateral to the somam Fig. 2B and C) or by action potentials initiated in the axon (by somatic current injection) which then back-propagate into the distal dendrites (average peak delta(F)/F amplitude of 16+-15% and average delta(F)/F decay time constant of 338+-54 ms, n=6). Thus synaptic stimulation which evoked regenerative all-or-none potentials in the distal dendritic branches, but only subthreshold PSPs at the soma, elicited a [Ca2+]i transient which remained largely localized to the distal apical dendrites."p.607
"Simultaneous measurement of dendritic membrane potential (Fig.3C, upper traces) and dendritic [Ca2+]i transients (Fig.3C, lower traces) evoked by current injection into distal dendrites via the recording pipette showed that a transient increase in [Ca2+]i was detectable already at potentials below -30 mV (Fig.3D). Both, the membrane voltage and the [Ca2+]i fluorescence transient increased abruptly when the stimulus intensity was increased and threshold was reached (Fig.§C and D). The average threshold potential for the initiation of all-or-none events was 26.4+-1.9 mV in seven recordings made 700-820 µm for the soma (Fig. 3C). The largest increase in dendritic [Ca2+]i amplitude ocurred concomitantly with the initiation of all-or-none regenerative potential (Fig. 3C and D). The peak of the [Ca2+]i fluorescence transient did not increase further with increasing stimulus intensity even when a somatic action potential was initiated by the stimulus, possibly reflecting significant non-linearity of the fluorescence indicator. Similar imaging results were obtained in one additional neuron."p.610
|
Fig. 2, 3
|
p.607, p.610
|
-
|
999704296
|
1000126375
|
|
1000126375
|
1000126375
|
999786975
|
Ca
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Addition of Cd2+ (200 µM) to the bath solution blocked both dendritic regenerative potentials and dendritic [Ca2+]i transients initiated by distal dendritic current injection (Fig. 4, n=7). This indicated that these responses were caused by the activation of voltage-dependent Ca2+ chanels and supports the view that the dendritic regenerative potentials represent local Ca2+ action potentials."p.610
|
Fig. 4
|
p.610
|
-
|
999786975
|
1000126375
|
|
1004375359
|
1004375359
|
315966505
|
I(CaL)
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Dihydropyridine antagonists are relatively selective for L channels..."p.1533
"Mean reduction of the HVA current was 31% (range 22-50%, n = 6, P < 0.001) for 5 µM nifedipine..."p.1534
"Both agents reduced the HVA current uniformly with no shift of the threshold of maximum current (Fig. 5, B and D). This fact alone suggests that the voltage dependencies of the residual components do not differ significantly from the blocked components and was confirmed by comparison of the activation curves constructed from tail currents (not shown)."p.1534
|
Fig. 5, 7
|
p.1533-1534
|
-
|
315966505
|
1004375359
|
|
1004375359
|
1004375359
|
315966505
|
I(CaN)
|
Ca2+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Whole-cell and single-channel recordings in mammalian neurons have provided evidence that omega-CgTx blocks N channels specifically (Plummer et al. 1989; Regan et al. 1991)."p.1533
"Mean reduction of the HVA current was ... 30% (range: 21-43%, n = 5, P < 0.001) for omega-CgTx."
"Both agents reduced the HVA current uniformly with no shift of the threshold of maximum current (Fig. 5, B and D). This fact alone suggests that the voltage dependencies of the residual components do not differ significantly from the blocked components and was confirmed by comparison of the activation curves constructed from tail currents (not shown)."p.1534
|
Fig. 5, 7
|
p.1533-1534
|
-
|
315966505
|
1004375359
|
|
1004375359
|
1004375359
|
1003935176
|
HVA-Ca
|
Ca2+
|
-
|
484.9+-42.3 pA
|
-
|
-45 mV
|
-
|
-15 mV
|
"The evoked current was blocked completely and reversibly by 200 µM cadmium (Fig.2 A) , but a small outward current was revealed at more depolarized potentials (Fig. 2B). As previously described (Sayer et al. 1990), the HVA current activated at potentials more positive than -45 mV and peaked near -15 mV. Maximum HVA current was 484.9 +- 42.3 pA, corrensponding to a current density of 27.7 +- 2.4 µA/cm^2 assuming a uniform distribution of channels on the membrane."p.1533
|
Fig. 2
|
p.1533
|
Detailed information on activation/inactivation kinetics and tail-currents.
|
1003935176
|
1004375359
|
|
1006790213
|
1006790213
|
-2086957548
|
I(K,fast)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"This lack of sensitivity of the fast K+ current to TEA allowed us to further investigate the kinetics of this current. The kinetics were quantified by fitting the fast K+ current to a Hodgkin-Huxley model. To increase the tail current amplitude the K+ concentration in the ACSF was increased to 65 mM. This change in K+ did not change the activation or deactivation kinetics of the fast K+ current (n = 7, data not shown). A Hodgkin-Huxley model with four activation gates (Fig. 4B) best desribed the activation and deactivation time course of the fast K+ current. The time constants, extracted from this analysis, ranged from 0.31 +- 0.03 ms at +80 mV (n=5) and displayed a bell-shaped dependence on voltage (Fig. 4C)."pp.625-626
"The inactivation time constant of the fast K+ current was measured by mono-exponential fits to the decay phase of the current (Fig. 5A). Above -20 mV the inactivation time constant was not dependent on voltage with a mean value of 8.0 +- 0.3 ms (n=5)."p.626
"The rate of recovery from inactivation ranged from 12.6 +- 1.5 ms (n = 5) at -110 mV to 64 +- 11 ms (n = 4) at -70 mV."p.626
"4-AP (3 mM) reduced the maximal amplitude of both fast and slow K+ currents as recorded following a voltage step to +80 mV (Fig. 6A). ... The concentration of 4-AP yielding half the current observed under control conditions was 4.2 +- 0.5 mM (Fig. 6B)."p.629
|
Fig. 4, 5, 6
|
pp.624-626
|
-
|
-2086957548
|
1006790213
|
|
1006790213
|
1006790213
|
-2086957548
|
I(K,slow)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"4-AP (10 mM) had no effect on the activation curve of the slow K+ current (Fig. 7A). ... The activation kinetics of the slow K+ current were quantified based on a Hodgkin-Huxley kinetic model in the presence of 9 mM 4-AP and 65 mM K+ in the ACSF. A Hodgkin-Huxley model with two activation gates (Fig. 7B) best described the time course of activation and deactivation of the slow K+ current. The time constants ranged from 2.4 +- 0.3 ms at +80 mV to 53 +- 4 ms at -50 mV and were fitted with a single exponential above -50 mV and another exponential below -50 mV."p.629
"The inactivation time constant of the slow K+ current was measured by fitting the decay phase of the current to a double exponential function as shown in Fig. 7A. ... The slow time constant, obtained from the double exponential curve fit, was slightly voltage sensitive and had a relative contribution of 57 +- 5% to the current (n =5, Fig. 8D) that was independent of voltage. The faster time constant was more dependent on voltage ranging from 1100 +- 80 ms (n = 6) at -10 mV to 290 +- 50 ms (n = 4) at +80 mV. ... The time constant of recovery from inactivation was calculated from mono-exponential fits of the maximal current amplitude during the second depolarising voltage step. The rate of recovery from inactivation ranged from 215 +- 12 ms (n = 6) at -110 mV to 1240 +- 230 ms (n = 4) at -70 mV."pp.629-630
"This double pulse protocol revealed that 10 mM TEA reduced the amplitude of the slow K+ current without significantly affecting that of the fast K+ current (Fig. 3A, n = 13)."p.624
|
Fig. 3
|
p.624
|
-
|
-2086957548
|
1006790213
|
|
1006790213
|
1006790213
|
-1610535617
|
I(K,fast)
|
K+
|
2.7 +- 0.5 pS/µm^2
|
-
|
-
|
-
|
-3 +- 1 mV
|
-
|
"Subtraction of the currents obtained by the two voltage protocols revealed a fast inactivating current (Fig. 1C). This "difference" current decayed with a time constant of 8.2 +- 0.6 ms (n = 5) at +80 mV to a sustained current (Fig. 1C). ... The difference current (Fig. 1C) will be referred to as the "fast" K+ current ..."p.623
|
Fig. 1, 2
|
p.623
|
Fit to Boltzmann functions, also for inactivation.
|
-1610535617
|
1006790213
|
|
1006790213
|
1006790213
|
-1610535617
|
I(K,slow)
|
K+
|
6.6 +- 0.7 pS/µm^2
|
-
|
-
|
-
|
-3 +- 1 mV
|
-
|
"This suggested that a 60 ms pre-pulse to -50 mV inactivated, in addition to a fast inactivating K+ current, a current with slower inactivation kinetics. ... while the current remaining after the -50 mV pre-pulse (Fig. 1B) will be reffered to as the "slow" K+ current."p.623
|
Fig. 1, 2
|
p.623
|
Fit to Boltzmann functions, also for inactivation.
|
-1610535617
|
1006790213
|
|
1927746281
|
1927746281
|
1006622979
|
I(A)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Plots of amplitude of I(A) and I(K) versus distance from the soma showed that both types of conductance were rather uniformly distributed along the primary apical dendrite, at least, for distances less than ~400 µm (Fig. 6B; n = 128 patches). The unconstrained fit of a straight line to the data points gave a slope of 2.3 pA/100 µm for I(A) and -0.4 pA/100 µm for I(K)."p.615
|
Fig. 6
|
p.615
|
K-channels in apical dendrite were activated by backpropagating action potentials.
|
1006622979
|
1927746281
|
|
1927746281
|
1927746281
|
1006622979
|
I(K)
|
K+
|
-
|
-
|
-
|
-
|
-
|
-
|
"Plots of amplitude of I(A) and I(K) versus distance from the soma showed that both types of conductance were rather uniformly distributed along the primary apical dendrite, at least, for distances less than ~400 µm (Fig. 6B; n = 128 patches). The unconstrained fit of a straight line to the data points gave a slope of 2.3 pA/100 µm for I(A) and -0.4 pA/100 µm for I(K)."p.615
|
Fig. 6
|
p.615
|
K-channels in apical dendrite were activated by backpropagating action potentials.
|
1006622979
|
1927746281
|
|
2026686061
|
2026686061
|
-20718951
|
I(Na)
|
Na+
|
58.7+-12 pS/µm^2
|
-
|
-
|
ca. -55 mV
|
-34.1+-1.7 mV
|
-
|
-
|
Table 1-2; Figs. 6-9
|
-
|
Kinetic parameters fitted; biexponential decay; ratio of slow to fast component of Na-current = 0.25+-0.051
|
-20718951
|
2026686061
|