CARDIOVASCULAR AND RESPIRATORY EFFECTS OF SERPASIL, A NEW CRYSTALLINE ALKALOID FROM RAUWOLFIA SERPENTINA BENTH, IN THE DOG

¹ Research Department, Ciba Pharmaceutical Products, Inc., Summit, N. J.

The cardiovascular and respiratory effects of Serpasil, a crystalline alkaloid obtained from Rauwolfia serpentina Benth, have been studied in the dog. Following the intravenous injection of Serpasil in a single dose of 0.5 to 1.0 mgm./kgm., a gradual persistent blood pressure and respiratory depression occurs in barbitalized dogs. A significant fall in blood pressure did not occur in five unanesthetized dogs following Serpasil administration.

The hypotension produced by Serpasil is initially due to vascular relaxation. However, this hypotension ultimately appears to be due to the antagonism by Serpasil of vasomotor reflexes necessary to compensate for a gradual progressive reduction in cardiac output which follows the administration of either Serpasil or its vehicle.

The occurrence of an increase in the A-V oxygen difference of venous origin without a concomitant significant increase in oxygen consumption is additional evidence of a vascular relaxation after the administration of Serpasil.

Although Serpasil produces a significant depression of the respiratory rate and volume of anesthetized dogs, arterial oxygen is not reduced to hypoxic levels.

Evidence indicating a central site of activity for Serpasil has been cited, confirmed and extended. The postulation has been presented and discussed that Serpasil produces a central inhibition of the sympathetic nervous system, possibly through specific hypothalamic depression.

Suggestions pertinent to the clinical use of Serpasil have been discussed.