THE ACTION OF ANDROMEDOTOXIN ON THE CAROTID SINUS IN DOGS

¹ Laboratory of Chemical Pharmacology, National Heart Institute, National Institute of Health, Public Health Service, Department of Health, Education, and Welfare, Bethesda 14, Maryland
² Department of Pharmacology, Emory University School of Medicine, Emory University, Georgia

1. The action of andromedotoxin on the carotid sinus in vagotomized dogs has been investigated.

2. Doses of intravenously administered andromedotoxin (8-20 microgm./kgm.) which are consistently hypotensive in vagotomized dogs either show no response or produce a pressor effect after bilateral denervation of the carotid sinus area.

3. Injections of minute doses of andromedotoxin (0.05 to 0.1 microgm.) into the adventitia of the innervated carotid sinus in vagotomized dogs with unilateral carotid sinus area denervation produce consistent depressor effects with partial or complete blockade of the carotid pressor reflex. Control injections of saline in equal volumes (0.1 ml.) are without effect. Rapid denervation of the carotid sinus during the hypotensive phase results in a sudden rise in blood pressure to hypertensive levels after which andromedotoxin by the intravenous route or by carotid sinus injection fails to produce a fall in pressure.

4. Andromedotoxin administered either intravenously or into the carotid sinus adventitia in two debuffered dogs with intact carotid bodies failed to elicit depressor responses. The latter structures, therefore, apparently play no role in this hypotensive action.

5. Neogermitrine and protoveratrine also showed the same type of responses demonstrating a close similarity in action between andromedotoxin and these veratrum alkaloids.

6. It is concluded that the hypotensive action of andromedotoxin is entirely reflex in nature. No central vasodepressor action has been demonstrated.