Cultured rat neurons and astrocytes express immunologically related epitopes of the GABAA/benzodiazepine receptor.

gamma-Aminobutyric acid (GABA) is the major inhibitory transmitter in the mammalian central nervous system (CNS) and an understanding of the development of receptors for this compound is of considerable interest. In this study, 3 monoclonal antibodies directed against the GABAA/benzodiazepine (GABA/BDZ) receptor were utilized in immunocytochemical experiments to localize receptor sites on neurons in dissociated cultures from fetal rat hypothalamus. Immunoreactivity was restricted to distinct patches on the plasma membrane of neurons. Analogous patches were observed on the surface of type 1 astrocytes, but not on type 2 astrocytes or oligodendrocytes. In membrane extracts from whole brain these antibodies reacted with two proteins (50 and 55 kDa) whereas extracts of cultured astrocytes yielded a single protein of approximately 63 kDa. Thus the identity of the glial protein remains unclear, but this study provides evidence for the presence of shared epitopes of the GABA/BDZ-receptor on both neurons and glia, and suggests that the astrocytic receptors may be important to nervous system function. Moreover it indicates that in vitro GABA/BDZ-receptors may form aggregates which would account for the restricted patterns of GABA sensitivity reported in some electrophysiological studies.