title: Neuronal and myogenic muscarinic effects of McN-A-343 on guinea pig longitudinal smooth muscle-myenteric plexus.
abstract: Among muscarinic agonists, the compound McN-A-343, originally proposed as selective stimulant of M1 cholinergic site, was subsequently questioned as a useful pharmacological tool in the classification of muscarinic receptors. In this work, evidence is presented for a dual response of McN-A-343 on longitudinal muscle-myenteric plexus preparation. On electrically-stimulated preparation, this agonist exhibited a pirenzepine-sensitive inhibition of the twitch contractions due to the involvement of neural M1-muscarinic receptor. On the other hand, a direct myogenic contractile action on the unstimulated tissue was observed using McN-A-343 in the same range of concentrations. This latter response, on the basis of the effects of muscarinic and non-muscarinic antagonists tested, seems to involve effectorial muscarinic sites with an unusual mechanism.
mesh_terms: D008455:(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride / Q000494:pharmacology*; D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009197:Myenteric Plexus / Q000187:drug effects*; D010276:Parasympatholytics / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000187:drug effects*
chemical_list: D010276:Parasympatholytics; D011976:Receptors, Muscarinic; D008455:(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride; D000109:Acetylcholine