Light and electron microscopic immunohistochemical demonstration of GABA-immunoreactive astrocytes in the brain stem of the rat.

Abstract

An antiserum against gamma-aminobutyric acid (GABA) was used in an immunohistochemical investigation of the nature of GABA-immunoreactive profiles in various regions of the brain stem of the rat. In accordance with findings in previous biochemical studies, but at discrepancy with recent immunohistochemical results, GABA-like immunoreactivity was demonstrated not only in neurons but also in glial cells. Electron microscopy revealed that the GABA-positive glial cells were astrocytes. Cells identified as oligodendrocytes were unlabelled as were pericytes and endothelial cells. In the labelled astrocytes, immunohistochemical reaction product was seen throughout the nucleus and cytoplasm, and in thin sheet-like processes surrounding neuronal elements and in end-feet lining the basal membrane of capillaries. These observations support the concept that astrocytes play a role in the metabolism of GABA. It is suggested that the failure to demonstrate the presence of GABA in glial cells in previous immunohistochemical studies may have been due to some factor in the tissue preparation. However, it is also possible that labelled glial cells may have been mistaken for small labelled neurons.