Effects of localized applications of L-glutamate on the population spike in the hippocampal slice preparation.

L-Glutamate applied exclusively to the CA3 cell body region of the rat hippocampal slice resulted in long-term potentiation (LTP) of the CA1 population spike evoked by Schaffer collateral stimulation. The same localized glutamate application to the CA1 area caused a prolonged depression of the response. These observations are consistent with the possibility that LTP is at least partly presynaptic and that the depression is due to an effect of glutamate on the postsynaptic elements and/or the presynaptic terminals.