A L-[H-3]GLUTAMATE BINDING-SITE ON GLIA - AN AUTORADIOGRAPHIC STUDY ON IMPLANTED ASTROCYTES

In the present study cultured astrocytes were implanted into the inferior colliculus of rats to create an astrocyte-enriched field that could be examined autoradiographically. The presence of the astrocytes was confirmed with anti-glial fibrillary acidic protein (GFA) immunocytochemistry. We report the presence of a chloride-dependent glutamate binding site on the implanted astrocytes. In the presence of chloride, the specific glutamate binding detected in the implant area was 5-fold greater than that found in a corresponding contralateral region. When the chloride was replaced with acetate, glutamate binding to the astrocytes decreased by more than 80%. The chloride-dependent binding to the astrocytes was insensitive to inhibition by kainic acid (KA) and N-methyl-d-aspartate (NMDA) and sensitive to quisqualate, l-aspartate, l-2-amino-4-phosphonobutyrate, and l-α-aminoadipate. The pharmacology of the binding was very similar to that of the in vitro glutamate binding to membranes from cultured astrocytes and to that of a chloride-dependent transport system identified in a glioma cell line. We conclude that the interaction of glutamate with astrocytes is an important component of the total glutamate binding observed in brain slices. © 1987.