Effects of methysergide on some cardiovascular responses in the anaesthetized rabbit.

Methysergide (0.1-5 mg/kg i.v.) caused dose-dependent reductions in the resting heart rate of anaesthetized rabbits. Resting mean arterial blood pressure was reduced only after the maximum dose. Methysergide 5 mg/kg significantly enhanced the pressor responses to i.v. phenylephrine and enhanced the accompanying bradycardia disproportionately. There was no evidence for a central increase in baroreflex gain, so an action of methysergide on baroreceptor sensory endings is suggested as a possible explanation.