Muscarinic inhibition of persistent Na+ current in rat neocortical
pyramidal neurons.
Thomas Mittmann and Christian Alzheimer.
Dept. of Neurophysiology, Ruhr-University Bochum, D-44780 Bochum, Germany.
Dept. of Physiology, University of Munich, D-80336 Munich, Germany.
APStracts 4:365N, 1997.
ABSTRACT
Muscarinic modulation of persistent Na+ current (INaP) was studied using
whole-cell recordings from acutely isolated pyramidal cells of rat neocortex.
After suppression of Ca2+ and K+ currents, INaP was evoked by slow
depolarizing voltage ramps or by long depolarizing voltage steps. The
cholinergic agonist, carbachol, produced an atropine-sensitive decrease of
INaP at all potentials. When applied at a saturating concentration (20 æM),
carbachol reduced peak INaP by 38 % on average. Carbachol did not alter the
voltage dependence of INaP activation, nor did it interfere with the slow
inactivation of INaP. Our data indicate that INaP can be targeted by the rich
cholinergic innervation of the neocortex. Because INaP is activated in the
subthreshold voltage range, cholinergic inhibition of this current would be
particularly suited to modulate the electrical behavior of neocortical
pyramidal cells below and near firing threshold.
Received 20 October 1997; accepted in final form 9 December 1997.
APS Manuscript Number J856-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 December 1997