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996756505
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Neurons FiringProperties
65 records
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means of pharmacological tests using agents acting on Ca2+, Na+ and K+
conductances.
Manipulations aimed at blocking different Ca2+ currents (13 neurons, each
perfused with several blockers) failed to impair bursting activity. In
Ca2+-free (Fig. 7A(3)) and Cd2+ or Co2+ (not shown)-substituted medium,
bursting activity often appeared to be enhanced, presumably though an
impairment of Ca2+-dependent K+ conductances. NiCl2 (up 1 mM) and amiloride
(up to 500 mM) (Fig.7A(2),B(2)), blocking the low threshold Ca2+ current [31],
as well as the other tested Ca2+ organic blockers, such as nicarpidine,
omega-conotoxin GVIA, and omega-agatoxin IVA (not shown in the figure) did not
change the shape and duration of burst discharges.
On the contrary, the pharmacological manipulations affecting Na+ currents were
found to be quite effective in the blocking bursting activity...Only perfusion
of TTX 0.5-1 µM reversed the IB firing mode to RS firing after 10-20 min,
before completely blocking the fast NA+ current responsible for APs; the first
derivative of the AP (Fig. 7C(4), inset) shows that burst disappearence
coincides with an initial reduction in the rise time of the AP."p.134-135.
