DIFFERENTIAL EXPRESSION OF CORTICOTROPIN-RELEASING HORMONE IN DEVELOPING MOUSE EMBRYOS AND ADULT BRAIN

CRH mRNA was detected by in situ hybridization histochemistry in numer ous regions of the adult mouse brain, including most prominently the p araventricular nucleus (PVN) of the hypothalamus, the inferior olivary nucleus, and Barrington's nucleus. After adrenalectomy, steady state CRH mRNA levels increased 1.7-fold, specifically in the PVN, consisten t with reports of negative glucocorticoid regulation of CRH expression in the rat PVN. Ontogenetic analysis of CRH expression in fetal and n eonatal mouse brain demonstrated CRH mRNA in PVN, Barrington's nucleus , olivary complex, and amygdaloid primordia on embryonic day 13.5. In contrast, CRH mRNA was not detectable in the cortex until after birth. CRH expression also exhibited differential regulation in ontogeny. CR H mRNA reached adult levels at markedly different times of development in each brain region, and CRH expression was reduced specifically in the PVN just before birth and the stress hyporesponsive period. High l evels of CRH mRNA were present transiently in the developing lung and celiac ganglion. The novel findings of CRH expression in fetal lung du ring the period of glucocorticoid-induced lung maturation and in celia c ganglion during development of the sympathetic nervous system indica te that CRH may have some important developmental functions in additio n to its role in activation of the stress response.