AJP - Cell Physiology, Vol 257, Issue 5 C1030-C1033, Copyright © 1989 by American Physiological Society
Existence of muscarinic suppression of a K current in PC-12 pheochromocytoma cells
K. Nakazawa, K. Fujimori, A. Takanaka and K. Inoue
Division of Pharmacology, National Institute of Hygienic Sciences, Tokyo, Japan.
Muscarinic influence on membrane currents of PC-12 pheochromocytoma cells
were investigated with whole cell voltage-clamp methods. An outward K
current was observed when depolarizing voltage steps were applied to the
cells. Methacholine (MCh, 300 microM), a selective agonist for muscarinic
receptors, partially suppressed the K current, and the suppression was
enhanced by removal of external Ca. The effect of MCh was antagonized by a
low dose (100 nM) of atropine. Nicotine (10 microM) induced an inward
current in these cells but did not affect the K current activated by
depolarizing voltage steps. A Ba current flowing through voltage-gated Ca
channels was not changed by MCh. The results indicate the existence of a
MCh-sensitive K current in PC-12 cells and suggest that the membrane
currents of these cells are modulated by cholinergic agents through
muscarinic mechanisms in addition to well-known nicotinic mechanisms.
