ULTRASTRUCTURAL-LOCALIZATION OF GLYCOGEN-PHOSPHORYLASE PREDOMINANTLY IN ASTROCYTES OF THE GERBIL BRAIN

The localization of glycogen phosphorylase in gerbil brain was determi ned by immunoelectron microscopy using the pre-embedding peroxidase te chnique. Electron-dense granular reaction product of peroxidase activi ty was observed in astrocytes of all brain regions examined (cerebral cortex, striatum, cerebellar cortex, hippocampal formation, corpus cal losum, mesencephalic trigeminal nucleus). The reaction product was dis tributed in a diffuse pattern throughout the cytoplasmic matrix of per ikarya and processes; sometimes the nucleus of labeled astrocytes also contains immunopositive material. The light microscopically visible g lycogen phosphorylase immunoreactivity associated with capillaries cou ld be characterized as a staining of astrocytic endfeet ensheathing ca pillaries. Endothelial cells and pericytes were never labeled. In addi tion to astrocytes, ependymal cells also presented immunopositive mate rial in their cytoplasm. On the other hand, no reaction product was ob served in cells identified as oligodendroglia or microglia. Neurons (w ith the exception of neurons of the mesencephalic trigeminal nucleus), their processes, and their synaptic endings were free of reaction pro duct. In the neuropil we frequently observed immunopositive glial proc esses adjacent to synaptic structures. This intimate spatial relations hip may be interpreted as a morphological sign of a metabolic interact ion. The data support the hypothesis that astroglia play a key role in glycogen metabolism and energization of the brain. (C) 1996 Wiley-Lis s, Inc.