title: Differential effect of verapamil on noradrenaline, carbachol, tyramine and 5-hydroxytryptamine induced contractions of the rat anococcygeus muscle.
abstract: The effect of verapamil and dantrolene sodium on the contractile responses evoked by noradrenaline, carbachol, tyramine and 5-hydroxytryptamine on the rat anococcygeus muscle was studied. Dantrolene sodium did not significantly antagonize noradrenaline, carbachol, tyramine and 5-hydroxytryptamine-induced contractions. Verapamil on the other hand, competitively antagonized 5-hydroxytryptamine-induced contractions while non-competitive antagonism was observed with tyramine and carbachol. Noradrenaline evoked contractions were unaffected. All agonists tested failed to produce a contraction in Ca++-free medium indicating that a transmembrane influx of Ca++ is involved in the contractile response to all these agonists. It is suggested that there are verapamil-sensitive and verapamil-insensitive calcium channels in the rat anococcygeus muscle.
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D003620:Dantrolene / Q000494:pharmacology; D004347:Drug Interactions; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D012701:Serotonin; D002217:Carbachol; D014700:Verapamil; D003620:Dantrolene; D002118:Calcium; D009638:Norepinephrine; D014439:Tyramine