Different expression of immediate-early genes in the rat paraventricular nucleus induced by stress: relation to corticotropin-releasing factor gene transcription.

Stressful stimuli induce the transcriptional activation of the corticotropin-releasing factor (CRF) gene as well as that of various immediate-early genes (IEGs). Among them, members of the fos/jun families play an important role in the regulation of gene expression. The possible relation between stress-induced IEG expression and CRF gene transcription was investigated by analysis of stress-induced changes in the abundance of c-fos, c-jun, jun-B, jun-D, and NGFI-B mRNA as well as CRF heteronuclear RNA (hnRNA), which reflects gene transcription, in the rat paraventricular nucleus (PVN) by in situ hybridization. Restraint stress induced rapid (within 5 min) and transient increases in the level of c-fos mRNA and CRF hnRNA in the PVN, with peak expression apparent 30 min after the onset of stress. The induction of jun-B and NGFI-B gene expression was also rapid and transient, but was delayed relative to that of c-fos mRNA and the CRF hnRNA. In contrast, both jun-D and c-jun were constitutively expressed in the PVN, and the amount of the corresponding transcripts increased only slightly in response to stress. These results reveal differential patterns of expression of IEGs in the PVN in response to stress. The observation that the level of mRNAs corresponding to these IEGs did not increase before that of CRF hnRNA may suggest that the products of these genes do not seem to directly mediate the stress-induced increase in CRF gene transcription in the PVN.