M1 and M2-muscarinic receptors in the epididymal half of the rat vas deferens.
The inhibitory effects of atropine and pirenzepine (nonselective and M1-selective antagonists, respectively) on the contractile responses of the epididymal half of the rat vas deferens to methacholine included a depression of the maximal response. In the presence of pirenzepine, atropine was a competitive antagonist of the responses to methacholine. However in the presence of atropine, pirenzepine remained a non-competitive inhibitor of the response. It is suggested that low concentrations of methacholine predominantly stimulate M2-receptors and that at high concentrations, methacholine also stimulates M1-receptors.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001570:Benzodiazepinones / Q000494:pharmacology; D004822:Epididymis / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008688:Methacholine Compounds / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects*; D009929:Organ Size / Q000187:drug effects; D010890:Pirenzepine; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects*; D014649:Vas Deferens / Q000187:drug effects
D001570:Benzodiazepinones; D008688:Methacholine Compounds; D011976:Receptors, Muscarinic; D010890:Pirenzepine; D001285:Atropine