DIFFERENTIAL SUBCELLULAR-LOCALIZATION OF 2 POPULATIONS OF GLUTAMATE AMPA RECEPTORS IN THE RAT TELENCEPHALON/

The distribution of glutamate AMPA receptors in the synaptosomal and m icrosomal fractions of neonatal and adult rat telencephalon was studie d by determining the saturation kinetics at equilibrium of H-3-AMPA an d H-3-CNQX binding. Al both ages, synaptosomal preparations exhibited two populations of H-3-AMPA binding sites with a small number of high affinity sites and a large number of low affinity sites. H-3-AMPA bind ing to microsomal preparations from both neonatal acid adult rat telen cephalon exhibited a much higher proportion of high affinity relative to low affinity sites. H-3-CNQX binding to the same fractions did not parallel H-3-AMPA binding, but was correlated with the low affinity H- 3-AMPA binding and with a marker of plasma membranes. The results sugg est that nonsynaptic glutamate/AMPA receptors have a high affinity for agonist and become low affinity when inserted into postsynaptic membr anes and that H-3-CNQX binds synaptic but not nonsynaptic glutamate/AM PA receptors with high affinity.