DEPRESSION BY REFLEXES OF THE PRESSOR AND CARDIOTOXIC RESPONSES TO OUABAIN

¹ Department of Pharmacology, Georgetown University School of Medicine and School of Dentistry, Washington, D. C.

The influence of the reflexogenic areas of the cardiovascular system on blood pressure effects and cardiac rhythm disorders produced by ouabain was evaluated in decerebrate cats. Ouabain (20,50 and 100 µg/kg), administered i.v., produced no significant rise in the mean arterial pressure of control animals but greatly increased the pressure in animals with sectioned buffer nerves (debuffered animals). Cutting the spinal cord or pretreating with phentolamine or with phenoxybenzamine significantly reduced this pressor response. In addition, both the lethal dose of ouabain and the time this agent took to induce ventricular fibrillation were significantly higher in the control group than in the debufiered group. These resuits show that ouabain is potentially capable of producing marked pressor responses which originate, in part, in the brainstem and are transmitted peripherally by the sympathetic nervous system. They also show that these responses are compensated for in the presence of the buffer nerves and that the compensatory mechanism confers some protection against the induction of fatal cardiac arrhythznias by ouabain.