A L-[3H]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-alpha-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.
D000110:Acetylcholinesterase / Q000032:analysis; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000637:transplantation; D001345:Autoradiography; D001667:Binding, Competitive; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D007245:Inferior Colliculi / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D000596:Amino Acids; D002712:Chlorides; D005971:Glutamates; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D018698:Glutamic Acid; D000110:Acetylcholinesterase