SOME CARDIOVASCULAR ACTIONS OF BENZQUINAMIDE

¹ Department of Pharmacology, Medical Research Laboratories, Chas. Pfizer & Co., Inc., Groton, Connecticut

Benzquinamide, a new benzoquinolizine derivative, was shown to increase blood pressure and heart rate of conscious dogs by oral and intravenous administration. This effect was abolished by sodium pentobarbital anesthesia or reserpine pretreatment.

In dogs anesthetized with sodium pentobarbital, benzquinamide, 0.5 mg/kg i.v., had no significant effect on blood pressure. At 10 to 20 mg/kg i.v., the drug lowered blood pressure and reduced the pressor effects to epinephrine and norepinephrine.

In dogs with blood pressure lowered by blood withdrawal or histamine infusion benzquinamide had a pressor effect in spite of sodium pentobarbital anesthesia. This effect was associated with a pronounced increase in cardiac output, force, and rate of cardiac contractions. Diehloroisoproterenol blocked the cardiac stimulant effect; phentolamine reduced the pressor effect of benzquinamide.

Benzquinamide had little or no pressor activity in dogs with the spinal cord sectioned at the 2nd cervical level. It had no cardiac stimulant activity in isolated perfused rabbit hearts and had no vasoconstrictor activity in dog hindlimb preparations. The experiments indicated that a functional central nervous system may be necessary for the hypertensive and cardiac stimulant actions of benzquinamide.