Open AccessM2 and M3 Muscarinic Receptors Couple, Respectively, With Activation of Nonselective Cationic Channels and Potassium Channels in Intestinal Smooth Muscle Cells
Author(s) -
Seiichi Komori,
Toshihiro Unno,
Takahisa Nakayama,
Hidenori Ohashi
Publication year - 1998
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.76.213
Subject(s) - muscarinic acetylcholine receptor , pirenzepine , carbachol , chemistry , muscarinic acetylcholine receptor m2 , muscarinic acetylcholine receptor m3 , muscarinic acetylcholine receptor m1 , receptor , biophysics , patch clamp , atropine , muscarinic acetylcholine receptor m5 , pharmacology , endocrinology , biology , biochemistry
Smooth muscle cells of guinea pig ileum express both M2 and M3 subtypes of muscarinic receptors. Under voltage clamp, activation of the muscarinic receptors with carbachol (CCh) induces Ca2+-activated K+ current (I[K-Ca]) and nonselective cationic current (Icat). Receptor subtypes mediating the current responses were characterized by using pirenzepine, AF-DX116, 4-DAMP and atropine, which have different profiles of the affinity constants for muscarinic receptor subtypes. The muscarinic antagonists inhibited either CCh-evoked I(K-Ca) or Icat with different potencies. Their relative potencies for I(K-Ca) and Icat inhibition resembled the relative affinity constants for M3 and M2 subtypes, respectively. Thus, the I(K-Ca) is mediated via the M3 subtype and the Icat via the M2 subtype.