AUTORADIOGRAPHIC STUDIES INDICATE REGIONAL VARIATIONS IN THE CHARACTERISTICS OF L-GLUTAMATE TRANSPORTERS IN THE RAT-BRAIN

Quantitative autoradiography of [H-3]L-aspartate binding in thaw-mount ed sections of rat brain has shown that L-trans-pyrrolidine-2,4-dicarb oxylate and D-threo-3-hydroxyaspartate but not DL-2-aminoadipate stron gly interacted with the binding sites while dihydrokainate, kainate an d beta-aminoadipate produced only weak effects. The potency of inhibit ors did not vary from one region to another in the telencephalon (neoc ortex, hippocampus and neostriatum) but, D-threo-3-hydroxyaspartate, L -trans-pyrrolidine-2,4-dicarboxylate, kainate and dihydrokainate inhib ited [H-3]L-aspartate binding in the cerebellar cortex less potently t han that in the forebrain. Characteristics of the known excitatory ami no acid transporters can, in part, explain the present results but con tributions from additional transporter molecules to the heterogeneity of [H-3]L-aspartate binding sites cannot be ruled out.