AMINO ACIDS RELEASED FROM THE CEREBRAL CORTEX IN RELATION TO ITS STATE OF ACTIVATION.

The rate of release of gamma-aminobutyric acid from the perforated pial surface of the cerebral cortex in the cat showed systematic variations with the state of activation or "arousal" of the electrocorticogram. In animals subjected to midbrain coagulation and showing constant spindle patterns characteristic of sleep, the rate of release was three times greater (about 2 micrograms per hour per square centimeter) than in animals showing a largely "aroused" electrocorticogram, which had sections of the upper cervical cord or were neuraxially intact but had been given local anesthesia. The rate of release of glutamic acid was lower in the "sleeping" animals than in "aroused" animals, while no such differences were found for glutamine and aspartic acid. Such studies may lead to a better understanding of chemical mechanisms involved in the control of states of consciousness by the brain stem.