Circulatory Reactions to Ergotamine and Effect Upon Them Produced by Adrenalectomy and the Blood pH.

Abstract

According to the observations of Rothlin, 1 Dale and Spiro, 2 and Schegg, 3 ergotamine tartrate in doses not exceeding 1.0 mg. per kilo given intravenously to cats and dogs produces a rise of blood pressure. Rothlin reported that very small doses also produced a slight fall of blood pressure in cats, but he ignored this observation in a later communication. 4 His blood pressure tracings showed that the pressor effect was not of exactly the same type. Some showed a persistent elevation of blood pressure while others showed a steep rise followed soon after by a prompt fall. But in all cases there was reversal of action of adrenalin when given soon after the administration of ergotamine.

In reinvestigating the action of this alkaloid we were impressed by the difference in the response of the circulation, under the same experimental conditions. Elevation occurred in some cats and depression was observed in others after the same doses of ergotamine, whatever the anesthetic, whether urethane or ether. The administration of adrenalin given by vein always produced a fall of blood pressure after the first or second doses of ergotamine. After repeated injection of ergotamine, adrenalin usually produced a slight rise of blood pressure, that is, reversal of effect was absent.

The depressor action of ergotamine was very severe and occurred in a large percentage of cases in some groups of experiments. AS this bore a striking resemblance to the effect produced by adrenalin given after ergotamine, it occurred to us that the function of the suprarenals might be a causative factor in the production of the depressor action of ergotamine. Removal of both adrenals confirmed our suspicion. In no case did a fall of blood pressure occur after ergotamine, such as was observed with the adrenals intact. There was elevation of blood pressure in more than 50% and no effect in the rest of the experiments. The negative results were probably due to trauma produced by excessive manipulation and exposure of the abdominal viscera in the course of the operation for the removal of the adrenals, which was made by the abdominal route.