LONG-TERM CHANGES IN GLIAL FIBRILLARY ACIDIC PROTEIN AND GLUTAMINE-SYNTHETASE IMMUNOREACTIVITIES IN THE SUPRAOPTIC NUCLEUS OF PORTACAVAL SHUNTED RATS

The present study was undertaken to ascertain whether, and to what ext ent, glial fibrillary acidic protein (GFAP) and glutamine synthetase ( GS) expressions in the supraoptic nucleus (SON) could be modulated aft er one month and six months of portacaval shunting (PCS) in rats. GFAP and GS immunoreactivities were significantly higher in PCS rats than in control rats at one and six months. The increased GFAP and GS immun oreactivities observed in the SON astrocytes were directly related to the duration of PCS. In PCS rats, the number and length of both GFAP a nd GS immunopositive astroglial processes increased not only in the hy pothalamic nucleus but in the perinuclear zone, where glutamatergic pa thways have been described, whereas GFAP and GS expressions decreased in the ventral glial lamina. Since GS is one of the glutamate metaboli zing enzymes and the SON is one of the areas of glutamatergic activity , our results show that astrocytes respond differentially to glutamate toxicity. This suggests that overexpression of GFAP and GS immunoreac tivities could be associated with glutamatergic neurotransmission diso rders.