POSTSYNAPTIC FACTORS IN THE EXPRESSION OF LONG-TERM POTENTIATION (LTP) - INCREASED GLUTAMATE-RECEPTOR BINDING FOLLOWING LTP INDUCTION IN-VIVO

Several lines of evidence indicate that LTP in the hippocampus is asso ciated with a change in the properties of postsynaptic glutamate recep tors. In the present study, we used quantitative autoradiography to ex amine the binding properties of the ha-amino-3-hydroxy-5-methyl-4-isox azole-propionate (AMPA) and N-methyl-D-aspartate subclasses of glutama te receptors in frozen brain sections obtained from rats in which perf orant-path LTP was induced in vivo. Induction of LTP resulted in a sel ective increase in [H-3]AMPA binding in those hippocampal subfields re ceiving perforant-path axons. Increases in [H-3]AMPA binding in dentat e gyrus (stratum moleculare) were highly correlated with the magnitude of LTP recorded in this structure. Scatchard analyses of [H-3]AMPA an d 6-cyano-7-nitro-[H-3]quinoxaline-2,3-dione (an AMPA receptor antagon ist) binding in the dentate gyrus indicated that LTP induction resulte d in an increase in the number of AMPA receptor binding sites. No chan ges in the binding of H-3-labeled N-[1-(thienyl)cyclohexyl]piperidine (an N-methyl-D-aspartate receptor antagonist) were observed in any hip pocampal subfield. These results suggest that a modification in postsy naptic AMPA receptors plays a role in the expression of synaptic enhan cement following LTP induction in the hippocampus.