Dissociation of changes in hypothalamic corticotropin-releasing hormone and pituitary proopiomelanocortin mRNA levels after prolonged stress exposure

Repeated immobilization stress for 7 days caused marked increase in cortico tropin-releasing hormone (CRH) mRNA in the paraventricular nucleus (PVN, 90 % above the control) and proopiomelanocoain (POMC) mRNA in the anterior pit uitary (73% above the control) in rats. Prolongation of the stress exposure to 42 days led to a decline of CRH mRNA response (42% above the control) i n comparison with that after 7 days, while POMC mRNA persisted at the same level. Observed adaptation of CRH but not POMC responses suggests that othe r factor(s) next to CRH participate in sustained rise in POMC expression du ring long-term stress. (C) 1999 Elsevier Science B.V. All rights reserved.