Glutamate and aspartate in cortical subarachnoid fluid in relation to convulsive activity

Abstract

Glutamic and aspartic acids were measured in subarachnoid fluid taken from the surface of the cerebral cortex of the dog. This fluid is considered to be representative of the interstitial fluid under conditions allowing sufficient time for the attainment of diffusion equilibrium. Samples were taken prior to injection of a convulsant and at various stages in the development of convulsive activity induced by thiosemicarbazide, pentetrazole, picrotoxin and methionine sulfoximine. The levels of glutamate and aspartate showed no tendency to increase during either the latent period or the occurrence of convulsive activity. It therefore appears unlikely that the seizures induced by these convulsants result from leakage of glutamate or aspartate from damaged cells, or from failure of uptake mechanisms, with accumulation to excitatory levels in the interstitial fluid.