Chemo- and baroreceptor innervation of the aortic trunk of the toad Bufo vulgaris.

In the toad Bufo vulgaris, afferent impulses were recorded from the fine branch of the vagus which terminates in the aortic trunk. Spontaneous single unit discharge was random. When the aorta was artificially perfused, units fired in response to flow change, hypoxia and hypoxia-hypercapnia of the perfusion fluid, and administration of NaCN or Ach. A few baroreceptor fibers fired synchronously with the blood pressure fluctuation. In anesthetized toads with other reflexogenic areas denervated, the intravenous administration of NaCN caused an increase in breathing and a slight elevation of blood pressure. When the nerve concerned was cut, these responses were abolished. Electrical stimulation of the nerve's central cut end brought about the same type of response as that to NaCN. Special cells closely resembling the glomus cells in the carotid labyrinth were found in the aortic wall. In amphibia, there is an aortic nerve corresponding to that of mammals, and the aorta is one of receptive areas predominantly contributing to respiratory control.