GLUCOCORTICOID RECEPTOR MESSENGER-RNA ONTOGENY IN THE FETAL AND POSTNATAL RAT FOREBRAIN

Glucocorticoid receptor (GR) ontogeny and distribution in postnatal ra t brain have been demonstrated, but onset and distribution of GR gene expression during fetal life has not been reported. This study focuses on the distribution of GR-mRNA in the fetal and postnatal rat forebra in, with emphasis on hypothalamic and limbic structures. Time pregnant rats were decapitated at 8:30-9:30 AM on Gestational Days 14 (F14), F 16, F17, F18, and F19. Postnatally, rats were sacrificed on Days 1, 4, 6, 10, and 16. Cryostat sections were subjected to in situ hybridizat ion, using a cRNA probe directed to the GR-mRNA. GR-mRNA was detectibl e in the hippocamposeptal formation as early as F14. By F16, GR gene e xpression was evident in the hypothalamic paraventricular nucleus (PVN ) as well. During late gestation (F17-F19), GR-mRNA was localized also in the thalamus, hippocampus, amygdala, and discrete cortical regions . Postnatally, GR-mRNA abundance was high in the PVN, CA1/CA2 hippocam pal field, piriform cortex and dorsal endopiriform nucleus, specific a mygdaloid nuclei, and the suprachiasmatic nucleus. In PVN, GR-mRNA was present prior to the onset of CRH gene expression (F17), which may su ggest a role for GR in neuronal differentiation. (C) 1994 Academic Pre ss, Inc.