INDUCTION OF GLIAL FIBRILLARY ACIDIC PROTEIN IMMUNOREACTIVITY IN THE RAT DENTATE GYRUS AFTER ADRENALECTOMY - COMPARISON WITH NEURODEGENERATIVE CHANGES USING SILVER IMPREGNATION

In the present study we performed a light microscopic anatomical compa rison of adrenalectomy (ADX)-induced neurodegeneration using silver im pregnation and reaction of astroglial cells using GFAP immunocytochemi stry in the hippocampus of the rat. Three survival times following ADX were studied: 24 hours, 3 days, and 3 weeks. Twenty-four hours follow ing ADX we found no degenerative changes or altered GFAP immunostainin g. Three days after adrenalectomy, argyrophilic somata appeared in the granular cell layer of the dentate gyrus. Argyrophilic dendrites were seen in the molecular layer of the dentate gyrus and neuritic argyrop hilia were seen in the messy fiber layer. Induction of GFAP immunoreac tivity occurred simultaneously with degeneration. Increased GFAP immun oreactivity could be observed 3 days after adrenalectomy in the molecu lar layer of the dentate gyrus, granular cell layer, sub and supragran ular cell layer, and messy fiber layer. Size and shape of astroglial c ells were changed, and their processes in the molecular layer changed from unidirectional to randomly organized. Degeneration and astroglial reaction were more pronounced 3 weeks after adrenalectomy and both we re prevented by adding corticosterone to the drinking solution. Animal s that did not show degenerative changes showed no increased GFAP immu noreactivity, while both effects were confined to the dentate gyrus an d messy fiber zone. These results show that there is a close relations hip between the induction of GFAP immunoreactivity in the hippocampus of the rat and neuronal degeneration in the dentate gyrus following AD X, both in time and space. (C) 1994 Wiley-Liss, Inc.