Distribution of microglia and astrocytes in different regions of the normal adult rat brain

The distribution of glial cells (microglia and astrocytes) in different regions of normal adult rat brain was studied using immunohistochemical techniques and computer analysis. Antibodies against lipocortin 1 (LC1) and phosphotyrosine (PT), as well as an isolectin, GSA B4 (GSA), were used for identification of microglial units, while antibodies against protein S100β allowed us to identify astrocytes. If LC1 was used as a marker, more microglial cells were detected than with the use of PT or GSA. The highest density of LC1-positive microglial cells (on average, 130±5 cells/mm2 of the brain section area) was found in the neostriatum, while the lowest density (51±4 cells/mm2) was observed in the medulla oblongata. In general, the density of an LC1-positive microglial population was higher in the forebrain and lower in the midbrain, and the smallest number of these cells was detected in the brainstem and cerebellum. The number of astrocytes was, on average, 2–3 times as large as the number of microglial cells. High density of astrocytes, was found in the hypothalamus and hippocampus (more than 260 cells/mm2); they were more, numerous in the white matter than in the gray matter. Lower densities of this type cells were observed in the cerebral cortex, neostriatum, midbrain, medulla oblongata, and cerebellum (less than 200 cells/mm2).