title: Effects of ergotamine on isolated human vessels.
abstract: In isolated human mesenteric and crural veins, ergotamine induced long-lasting contractions. These contractions were resistant to repeated wash-out and were not affected by alpha-adrenoceptor blockade, but could be abolished by removal of extracellular calcium or by the presence of the calcium-blocker nifedipine. In contrast to its effect on human mesenteric and crural veins, ergotamine had no contractile effect, but a marked relaxant effect on mesenteric arteries mediated via blockade of alpha-receptors. The ergotamine-induced contraction was not affected by indomethacin (0.28--2.8 microM) nor was it influenced by serotonin (5-HT). In both mesenteric and crural veins, the ergotamine-induced contraction was diminished by the 5-HT blocking agent, methysergide. In veins, development of tachyphylaxis to 5-HT was demonstrated. It is concluded that ergotamine has a direct contractile effect on isolated human mesenteric and crural veins. These effects are dependent on unhindered influx of extracellular calcium and are at least partly mediated via 5-HT receptors. In mesenteric arteries, ergotamine acted as an alpha-adrenoceptor blocker, and had no contractant effect.
mesh_terms: D000328:Adult; D000368:Aged; D004347:Drug Interactions; D004878:Ergotamine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology
chemical_list: D012701:Serotonin; D004878:Ergotamine; D011188:Potassium; D009638:Norepinephrine; D007213:Indomethacin; D008784:Methysergide; D010646:Phentolamine