Inhibitory Effect of Vasopressin on Cardio-Accelerator Mechanism After Sino-Aortic Denervation

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Abstract
Effects on heart rate of rapid intraven. injn. of vasopressin, 1.5 units, were detd. in unanesthetized dogs having the sino-aortic pressore-ceptive areas denervated. Additional operations had been performed in some of the animals. The tonic cardio-accelerator activity seen in these animals is decreased or suspended following injn. of vasopressin. The inhibitory effect of vasopressin on cardio-accelerator activity is not dependent on afferent influences from structures below the level of the diaphragm; it is not related to the oculocardiac reflex, and does not appear to be related to anoxia in the central nervous system. Vasopressin does not interfere with the cardio-accelerator action of epineph-rine and has no direct inhibitory effect on the sino-auricular node. The inhibition occurs somewhere in the accelerator pathway within the central nervous system or at the level of the cardio-accelerator center.