The effect of various concentrations of L-glutamate on neurotranslnission in the CA1 hippocampal area was studied using hippocampal slices. Three intervals of L-glutamate concentration were established: _<1 mM (all studied parameters are completely reversible upon washout, transmission being preserved), from 1 to 10 mM (both responses to frequency stimulation and single population spikes remain partially suppressed after washout), and above 10 mM (more than 50% suppression of transmission persists after washout).