FosB is a member of the Fos family transcription factors. To determine whether FosB expression is regulated by glucocorticoids (GCs) in the hypothalamus, rats underwent sham adrenalectomy (sham-ADX) or bilateral ADX, and FosB/ΔFosB (ΔFosB, a truncated splice variant of FosB)-immunoreactivity (ir) was determined in the paraventricular nucleus (PVN) and supraoptic nucleus (SON). In the parvocellular division of the PVN (paPVN) and SON, FosB/ΔFosB-immunoreactivity (ir) increased significantly following sham-ADX compared to naive rats, which was suppressed with either corticosterone (CORT) or dexamethasone (DEX). Following ADX, the increase in FosB/ΔFosB-ir was much more prominent than that in the sham-ADX group, and the ADX-induced robust increase was suppressed by CORT or DEX, but not by aldosterone. Stressless removal of CORT from drinking water did not induce FosB/ΔFosB-ir in either the PVN or SON, and thus the up-regulation of FosB/ΔFosB-ir following ADX was dependent on the systemic stress associated with surgery. In the paPVN, the majority of corticotrophin-releasing hormone (CRH) neurones co-expressed FosB/ΔFosB-ir following ADX, whereas, in the magnocellular division of the PVN, vasopressin (AVP) and oxytocin (OXT) neurones did not express FosB/ΔFosB-ir. In the SON, approximately 40% of the AVP neurones co-expressed FosB/ΔFosB-ir following ADX, but the OXT neurones were devoid of FosB/ΔFosB-ir. In concert with these results obtained in vivo, DEX suppressed the forskolin-induced increase in FosB gene promoter activity in a homologous hypothalamic cell line. These results suggest that GCs may be a potent regulator of FosB/ΔFosB expression, which is induced by stress, in hypothalamic neuroendocrine neurones.
- Corticotrophin-releasing hormone
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience