Concentration of Lactic Acid in Rat Brain during Natural Sleep

Abstract

PROGRESS in neurophysiology has made it possible to describe the state of sleep objectively and to draw a distinction between two phases of sleep in various mammals : (a) sleep in which waves in the electroencephalogram are slow and of high voltage (slow wave sleep); (b) activated sleep with fast waves of low voltage in the electroencephalogram, associated with the disappearance of tonic discharge of the neck muscle. No attempt has been made, however, to examine the chemical constituents of the brain during the two phases of sleep. Lactic acid in the rat¹ and ammonia in the dog² are among the labile constituents which have been reported to change in concentration in the brain concomitantly with the cycle of sleep–wakefulness. In these experiments, however, the state of sleep of the animals was judged by their behaviour. The present investigation was carried out to examine the relationship between the biochemical and electrophysiological changes of the brain in various stages of natural sleep.