Thirty-fifty mg/kg of pargyline bid was given ip to 51 rats

15 dogs and 4 cats on the day before experiments. The animals -were anesthetized during experiments and the changes of blood pressure to reserpine 2 mg/kg iv were observed. 40 aortic strips and 10 isolated auricles were taken from rabbits which were treated previously with pargyline 120 mg/kg bid ip. The changes in aortic strip contraction and auricular beat rate to reserpine added into organ bath were recorded. The results obtained indicated that in the animals treated previously with MAOI pargyline

there was a conspicuous reverse of depressor effect of reserpine to pressor one

and that reserpine produced a mild contraction of aortic strips and a slight increase in beat of isolated auricles. The cardiovascular stimulant actions of reserpine could be antagonized by a-receptor blockers

phentolaraine or chlorpromazine

whereas the increase in amplitude of pulse pressure could be decreased by B-receptor blocker

propranolol. From these results it is suggested that the mechanism of pressor action is peripheryl adrenergic in nature. The present paper further confirms that pargyline and resorpine cannot be used sequentially in clinical combinations of antihypertensive drug therapy.