RESUMEN
The effects of a herbal drug, Ajmaloon (Hamdard, India), on the arterial blood pressure, heart rate (HR) and baroreceptor-heart rate reflex were studied in anesthetized rabbits and monkeys. Intravenously administered Ajmaloon produced a dose-dependent hypotensive response in both the species without any significant effect on the heart rate. Only in high doses (200 mg/kg or more). Ajmaloon produced a bradycardia response in rabbits. Even the highest dose (300 mg/kg) of Ajmaloon used in the present investigation did not cause arrhythmia or any other conduction disorder or respiratory distress. Baroreflex SAP-HR curve was shifted to the left of the control following treatment with 100 mg/kg intravenous Ajmaloon in both the species. Loss of tachycardia response to fall in arterial pressure in Ajmaloon treated animals indicated the drug induced suppression of normally existing sympathetic excitatory influence in response to hypotension. Baroreflex regulatory HR response to hypertension remains intact after intravenous administration of 100 mg/kg Ajmaloon, a dose much higher than the prescribed highest oral dose for humans. Intact baroreflex regulation of arterial blood pressure in response to hypertension in Ajmaloon treated mammals suggests that in patients besides lowering the blood pressure. Ajmaloon might not interfere with the normal blood pressure regulatory mechanism through arterial baroreceptors during hypertension.