1990 Volume 102 Issue 11-12 Pages 1373-1384
The naturally-occurring dicarboxylic amino acids, L-glutamate (Glu) and L-aspartate, are the principal neurotransmitter candidates for excitatory synaptic transmission in vertebrate central nervous systems. The receptors activated by these amino acids are classified by their most selective and potent agonists, i.e., N-methyl-D-aspartic acid (NMDA), kainic acid, and quisqualic acid.
In this study, I examined the effects of NMDA on behavior, electroencephalogram (EEG), and brain amino acids levels after intraventricular injection in mice. When NMDA was intraventricularly injected into mice, running fits were observed 10-30 seconds after injection, followed by a sedative phase and returned to a normal behavior within 15-20 minutes after injection. In the EEG, middle voltage fast waves were observed 10-20 seconds after injection, followed by EEG suppression for a few minutes and the appearance of high voltage slow waves 4-5 minutes after injection. About 20 minutes after the injection the EEG was normal. No spike discharge was observed during this observation. Glu levels increased in the hippocampus during running fits, while GABA levels decreased in the cerebellum and hippocampus before running fits, and increased in the cerebellum 10 minutes after NMDA injection. The taurine level decreased in the striatum before running fits. All amino acids observed recovered to control levels 60 minutes after NMDA injection. These results indicate that the NMDA-induced running fits are not accompanied by spike discharges in the EEG, and are related to Glu and GABA neurons.
