title: Chronotropic effects of droperidol.
abstract: To study the mechanism of action by which droperidol exerts a negative chronotropic effect, 3 series of experiments were performed: a) on isolated right atria of rabbits, b) on the isolated vas deferens of guinea-pigs and c) by injecting the drug directly into the sinus node artery of anesthetized dogs. Isolated tissue results include: lack of cholinergic action or beta-adrenergic antagonism: a calcium ion flux interference could not be demonstrated. Alpha adrenergic antagonism of the drug (pA2) was ascertained in the vas deferens. Injections of droperidol in the sinus node artery caused a negative chrontropic effect proportional to the dose and arrest ensued with the largest dose followed by His escape rhythm. Droperidol could not inhibit isoproterenol or dopamine-induced tachycardia and showed similar negative chronotropism in vagotomized and atropinized dogs. Negative chronotropic effects of the drug appear to be caused by an exit blockade of sinus impulses.
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004329:Droperidol / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007267:Injections; D007545:Isoproterenol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D009538:Nicotine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D012849:Sinoatrial Node; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D011189:Potassium Chloride; D009538:Nicotine; D001285:Atropine; D007545:Isoproterenol; D004329:Droperidol