title: Existence of muscarinic suppression of a K current in PC-12 pheochromocytoma cells.
abstract: 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.
authors.affiliation: Division of Pharmacology, National Institute of Hygienic Sciences, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Nakazawa
authors.forename: K
authors.initials: K
authors.lastname: Fujimori
authors.forename: A
authors.initials: A
authors.lastname: Takanaka
authors.forename: K
authors.initials: K
authors.lastname: Inoue
mesh_terms: D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004594:Electrophysiology; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D010673:Pheochromocytoma / Q000473:pathology / Q000503:physiopathology*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D008688:Methacholine Compounds; D010277:Parasympathomimetics; D016210:Methacholine Chloride; D001285:Atropine; D011188:Potassium; D002118:Calcium