RU-486 BLOCKS STRESS-INDUCED ENHANCEMENT OF PROENKEPHALIN GENE-EXPRESSION IN THE PARAVENTRICULAR NUCLEUS OF RAT HYPOTHALAMUS

The purpose of this study was to investigate the glucocorticoid (GC) m ediated regulation of corticotropin-releasing hormone (CRH) and proenk ephalin (PE) gene expressions in the paraventricular nucleus (PVN) of the hypothalamus during physical stress induced by a single intraperit oneal (i.p.) injection of hypertonic saline (9% NaCl). Previous intrac erebroventricular (i.c.v.) administration of the type II glucocorticoi d receptor (GR) antagonist RU-486 (20 ng/rat), increased the basal CRH mRNA levels in the PVN but had no effect on PE gene expression. Stres s induced by injection of hypertonic saline increased both CRH and PE mRNA levels in PVN. Administration of RU-486 completely blocked the st ress-induced increase of PE mRNA levels, but failed to alter the CRH m RNA levels in the PNV. These data suggests that, under these experimen tal conditions, endogenous GC are necessary for a normal PE response t o hypertonic saline stress. (C) 1998 Elsevier Science B.V.