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B00b
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Literature
38 records
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cell-attached and outside out patches from large layer 5 cortical pyramidal
neurons of the rat.
patches from the soma and primary apical dendrite of large layer 5 pyramidal
neurons in acute slices of rat sensorimotor cortex (22-25 degrees C). Ensemble
averages revealed that some patches contained only fast, I(A)-like channels,
other contained only I(K)-like channels that did not inactivate or inactivated
slowly, and the remainder contained mixtures of both types. I(A) and I(K)
channels had mean unitary conductances of 8.5 and 20.3 pS, respectively, and
had distinctive patterns of gating. Peak activation curves for
ensemble-averaged currents were described by the Boltzmann equation with
half-maximal voltage [V(1/2)] and slope factor (k) values of -24.5 mV and 16.9
mV for I(A) and -7.6 mV and 10.1 mV for I(K) (patches < 250 microm from the
soma) or -22.9 mV and 16.2 mV for I(A) (patches > 250 microm from the
soma). The steady-state inactivation curve for I(A) gave V(1/2) and k values
of -72.3 mV and -5.9 mV (< 250 microm from the soma) or -83.1 mV and -6.5
mV (> 250 microm from the soma). These values were similar to the
corresponding data for I(A) and I(K) in nucleated patches from the same cell.
The amount of I(A) and I(K) present in patches depended weakly on distance
along the primary apical dendrite from the soma. The amplitude of I(A)
increased, on the average, by 2.3 pA per 100 microm, while the amplitude of
I(K) decreased by 0.4 pA per 100 microm. I(A) and I(K) channels in dendritic
cell-attached patches were activated by the passage of a back-propagating
action potential past the tip of the patch electrode. These results show
directly that these potassium channels participate in action potential
repolarisation, and thus contribute to the process of synaptic integration in
these neurons.
