Spontaneous Activity recorded from the Central Cut End of the Carotid Sinus Nerve of the Cat

Abstract

THE receptor in the carotid body for changes in blood gas tensions has for many years been assumed to be the glomus cell^1,2 or Type I cell³. Lever, Lewis and Boyd⁴ showed by electron microscopy that the nerve endings adjacent to these cells contain microvesicles, of the same dimension as synaptic vesicles, and small mitochondria, and this observation was confirmed by Biscoe and Stehbens^5,6, who described the structure of the endings in greater detail and showed that they are similar to those of an efferent type in other parts of the nervous system⁷ and share a dense junctional region with the Type I cell membrane. Biscoe and Stehbens⁸ later found that the endings degenerated after the carotid sinus nerve was cut, and it seemed probable, in accordance with the evidence of De Castro^1,2, that they were afferent nerve endings. It is also possible, however, that such endings arise from efferent nerve fibres coursing in the carotid sinus nerve to the carotid body. The purpose of the present experiments was to seek evidence for such efferent fibres.