SELECTIVE INCREASE IN ASTROCYTIC ELEMENTS IN THE RAT DENTATE GYRUS AFTER CHRONIC TOLUENE EXPOSURE STUDIED BY GFAP IMMUNOCYTOCHEMISTRY AND ELECTRON-MICROSCOPY

Using glial fibrillary acidic protein (GFAP) immunohistochemistry, and electron microscopy, we examined changes in the features of astrocyte s in the dentate gyrus of the hippocampal formation after high-dose ch ronic toluene inhalation (2000 ppm, 4 h/day) for 1 month. In toluene-t reated rats, the numbers of GFAP-immunoreactive (IR) astrocytes were n ot changed, whereas the area and intensity of GFAP-IR processes were i ncreased markedly in the dentate gyrus. In addition, dense, thick and highly-stained GFAP-IR processes appeared entering into the granular c ell layer, compared with those of controls. At the electron microscopi c level, numerous astrocytic processes with high electron density inte rvened between the granular cells. These results suggest that high-dos e of chronic toluene exposure induces morphological changes in astrocy tes in the dentate gyrus of the hippocampal formation.