REVERSIBLE CHANGES IN GLUTAMINE LEVELS IN THE CAT CEREBRAL CORTEX EVOKED BY AFFERENT ELECTRICAL STIMULATION AND BY ADMINISTRATION OF PENTAMETHYLENETETRAZOLE (PENTYLENETETRAZOL)

—1. Levels of glutamine and glutamate were measured in cat cerebral cortex rapidly frozen in situ after 30 sec of afferent electrical stimulation (AES) of the contralateral brachial plexus. A substantial decrease in glutamine and a minor one in glutamate were found as compared to the ipsilateral cortex. The fall in glutamine was found to be reversed very shortly after break of the current. 2. Glutamine levels of the cortex determined after rapid freezing in situ were found to fluctuate with the diverse stages of periodic convulsions induced by pentylenetetrazol (PTZ): glutamine was substantially decreased during the initial part of the first clonictonic convulsion, it returned to the normal value in its termination stage and remained so at the commencement of the interictal recovery period, dropping again shortly before the onset and in the course of the second convulsion. The second drop in glutamine was accompanied by a decrease of glutamate. In the comatose state which followed convulsions, both glutamine and glutamate were again at their original concentrations. 3. The results suggest that the view of the metabolic stability of brain glutamine under cerebral stimulation—based on past reports—should be modified in the sense that glutamine is labilized by excitation, but this effect is obscured by the counteracting process of synthesis de novo. 4. The significance of the data reported here, in relation to the incidence and termination of convulsions, as well as the mechanisms which may be involved in the observed fall and restitution of the level of cerebral glutamine, are discussed.