On the mode of action of ergometrine in the isolated dog coronary artery.

Coronary vasoconstrictor responses to ergometrine were examined in spiral coronary arterial preparations of dogs. Either ergometrine or serotonin (5-HT) produced dose-dependent contractions of the strips. Methysergide significantly depressed the contractions induced by ergometrine or 5-Ht. Dihydroergotamine and phentolamine depressed constrictor responses to ergometrine, while phenoxybenzamine did not. The 5-HT antagonistic action of phentolamine was stronger than that of phenoxybenzamine. The results indicate that ergometrine may act on coronary arteries mainly through activation of 5-HT receptors.