CARDIOVASCULAR EFFECTS OF PIPERINE IN ANESTHETIZED DOGS

Cardiovascular responses to intravenous administration of piperine wer e investigated in anaesthetized dogs. Piperine produced biphasic effec ts on the arterial blood pressure, depressor and presser effects. In t he presence of vagus nerves, low doses of piperine (0.25-0.5 mg kg(-1) ) caused a transient drop in arterial blood pressure, a marked bradyca rdia and apnea. With higher doses of piperine (1.0-1.5 mg kg(-1)), a t ransient drop in blood pressure was followed by an overshoot of pressu re and then a rapid return to normal. Bilateral vagotomy or atropine i njection (1.0 mg kg(-1)) abolished the bradycardia and the fall of blo od pressure caused by piperine. Regarding the presser effect, piperine produced a positive inotropic effect with no chronotropic action. Ver apamil (0.15 mg kg(-1)), a calcium channel blocking agent, completely abolished the overshoot of blood pressure. These results suggest that the depressor effect of piperine is associated with a cholinergic mech anism whereas the presser effect is related to an influx of Ca++ into the muscle cells probably into the cardiac and vascular smooth muscle cells.