Verapamil: A selective antagonist of constrictor substances in dog coronary artery: Implications for variant angina

Abstract

Canine circumflex coronary artery ring segments were contracted in vitro by ergometrine, serotonin, phenylephrine, noradrenaline (with propranolol) and a thromboxane A2 analogue, U46619. Ergometrine was classified as a serotonin agonist since concentration-response curves were competitively inhibited by methysergide but not by α-adrenoceptor antagonists. Glyceryl trinitrate (IC50 18.6 nmol/l) relaxed the coronary rings precontracted with serotonin, phenylephrine or U46619. In contrast (±)-verapamil (0.1-10 μml/l) was more effective against serotonin than phenylephrine or noradrenaline and was almost inactive against U46619. In a blood perfused left anterior descending coronary artery prepara..