THE SITE OF CARDIOVASCULAR ACTION OF VERATRUM DERIVATIVES

¹ Department of Pharmacology, Boston University School of Medicine, Boston 18, Mass.

A series of cross circulation experiments modified after Heymans and Heymans (1926) has been utilized to separate the actions of four hypotensive veratrum alkaloids when confined to the head from actions when confined to the body of dogs anesthetized with pentobarbital. Doses used were well within the clinical range and were equihypotensive by mammalian assay.

It was found that Veriloid, protoveratrine, veratridine and veratramine when confined to the head of the dog with carotids innervated and vagi intact produced only hypotension without alteration of heart rate. This hypotension was still evoked by each derivative after atropine or vagotomy. It was not decreased by carotid denervation.

It was found that all four derivatives confined to the body produced both bradycardia and hypotension. Atropinization or vagotomy eliminated all response to body administration after Veriloid or protoveratrine. Administration of veratridine or veratramine to the body after atropine still evoked a slight bradycardia and hypotension.

The convulsant action of veratramine was found to be a central action.

The relative importance of the reflexly and the centrally induced hypotensive actions of veratrum are discussed. It is concluded that the central action appears on present data to be more important. No evidence of a centrally or carotid-body-induced bradycardia was observed.

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