Effects of Barbiturates and Lack of Oxygen on the Monosynaptic Reflex Pathway of the Cat Spinal Cord

Abstract

General anaesthetics or lack of oxygen block the monosynaptic reflex in the spinal cord if the level of anaesthesia or oxygen deprivation are great enough. Lack of oxygen, whether induced by breathing gas of low oxygen content (hypoxia, anoxia) or by stopping ventilation or circulation (asphyxia), gives an initial period of enhanced reflex activity before block occurs (see Kirstein 1951). Many investigators have expressed different opinions about the differential sensitivities of the various parts of the spinal reflex pathway to both anaesthetics and lack of oxygen, about the site of blocking, and the mechanism of their action. Some of the differences can presumably be explained by differences in experimental techniques. The present investigation was designed to establish the principal site of action of barbiturates and hypoxia and their effects before block occurs on the various components of the monosynaptic reflex pathway within the cat spinal cord.