Succinic Dehydrogenase Activity in Brain Tissue of Rats after Ovariectomy and Steroid Administration

Abstract

ANÆSTHETIC properties of certain steroids have been demonstrated by Selye¹, and Michaelis and Quastel² have stated that anæsthetic activity depends on inhibition of the utilization of glucose and oxygen by brain tissue. Later, Gordan and Elliott³ showed that addition of certain steroids to brain cells in vitro produced a prompt inhibition of the rate of uptake of oxygen by these cells. Conversely, in castrated male rats, that is, in animals deficient in gonadal steroids, the uptake of oxygen by the brain increased up to 35 per cent^4,5—a fact which suggests that the steroids, by virtue of their inhibiting effects, act as brakes on cerebral metabolism. Further experiments indicated that the known anæsthetic potency of the steroids parallels their degree of inhibition⁶. The site of the steroid inhibition has since been found to be at the dehydrogenase-level rather^7,8 than the cytochromes, where other anæsthetic agents exert their effects. Thus, the distinctive effects of steroids on the respiratory metabolism of tissues can be ascertained by means of the quantitative analysis of the dehydrogenase activity under conditions of steroid administration or deficiency.