Responsiveness of isolated canine cerebral and peripheral arteries to ergotamine.
Changes in tension of spiral strips from dog saphenous, external carotid and basilar arteries were monitored isometrically. Serotonin (5-HT) contracted the 3 arterial preparations in about the same concentration range. Compared with noradrenaline (NA) (100%) the efficacy of 5-HT was about 60% on saphenous, 150% on external carotid and about 500% on basilar arteries. Ergotamine (E) stimulated the 3 vascular preparations in concentrations about 100 times lower than 5-HT. Compared with NA the efficacy of E was about 20% on saphenous, 50% on external carotid and 200% on basilar arteries. Compared with 5-HT (100%) however, E had similar constrictor activities in the 3 arteries. It seemed likely therefore that 5-HT receptors are involved in the vasoconstrictor activity of E. Evidence for this was obtained in experiments in which cyproheptadine (Cy), a 5-HT antagonist, was used. For antagonism of E concentrations of Cy about 6 times higher than those required to inhibit 5-HT were necessary, whereas for antagonism of NA about 500 times higher Cy concentrations were necessary. The results suggest that on canine arterial vascular smooth muscle the constrictor activity of E is mediated mainly through serotoninergic receptor sites.
D000818:Animals; D001158:Arteries / Q000187:drug effects*; D001488:Basilar Artery / Q000187:drug effects; D002342:Carotid Artery, External / Q000187:drug effects; D002536:Cerebral Arteries / Q000187:drug effects*; D003533:Cyproheptadine / Q000494:pharmacology; D004285:Dogs; D004878:Ergotamine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists; D014666:Vasomotor System / Q000187:drug effects*
D012702:Serotonin Antagonists; D003533:Cyproheptadine; D012701:Serotonin; D004878:Ergotamine; D009638:Norepinephrine