title: Mechanism of action of B-HT 933 (azepexole) in rat vas deferens and guinea-pig ileum.
abstract: The mechanism of action of B-HT 933 (azepexole) was studied on the rat vas deferens and myenteric plexus-longitudinal muscle (MP-LM) of the guinea-pig ileum. The drug caused a concentration-dependent inhibition of the twitch response in both preparations. The maximal inhibition in both preparations was 80-90%. B-HT 933 did not affect the cumulative dose-response curves of the vas deferens and of MP-LM to noradrenaline (NA) and acetylcholine (Ach) respectively. Yohimbine antagonized in a competitive way the twitch inhibitory effect of B-HT 933 on vas deferens and on MP-LM; the pA2 values were 8.62 and 8.5, respectively. The twitch inhibitory effects of B-HT 933 were not antagonized by propranolol. The results suggest that the action of B-HT 933 is mediated by stimulation of presynaptic alpha 2-receptors.
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013569:Synapses / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D001381:Azepines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011433:Propranolol; C015603:azepexole; D000109:Acetylcholine; D009638:Norepinephrine