The hypotensive effect of PAMC and its mechanism were studied.In conscious renal hypertensive rats, intraperitonal injection of PAMC once a day for 7d at the dosage of 11 mg/kg ( 1 time/day ) and oral administration of the drug 3 times a day for 14 d at the dosage of 12 mg/kg/d, the arterial pressure decreased 29.0?2.8% and 20.3 ? 1.4%, respectively.In normal anesthetized dogs and rats, intravenous injection of PAMC at the dosage of 0.4 mg/kg, the mean arterial pressure deceased 43.7 ? 7.9 and 39.7 ? 2.3%. In anesthetized rabbits and rats, intraduodenal injection of PAMC at the dosage of 4 mg/kg, the mean arterial pressure decreased 24.5 ? 3.8% and 38.2 ? 11.4%, respectively.The experiments suggested that inhibition of the (?) -adrenal receptors may be the principal mechanism of the hypotensive action of PAMC. Ganglion blockade, vasodilation as Well as excitation of ?2-adrenal receptors may also be involved.The acuts iv PAMC LD50 in mice were 25.5?5.0 mg/kg.