Impaired adaptation to repeated restraint and decreased response to cold in urocortin 1 knockout mice

Abstract

Urocortin 1 (UCN1) is a corticotropin-releasing factor (CRF)-like peptide whose role in stress is not well characterized. To study the physiological role of UCN1 in the response of the hypothalamic-pituitary-adrenal (HPA) axis to stress, we generated UCN1-knockout (KO) mice and examined their adaptation to repeated restraint and to cold environment. Wild-type (WT) and UCN1-KO animals were restrained hourly for 15 min from 9 AM to 2 PM, and blood samples were obtained for corticosterone measurement. WT animals adapted to repeated restraint with a decreased corticosterone response; the restraint-stimulated corticosterone levels fell from 215 ± 31 ng/ml in naïve animals to 142 ± 50 ng/ml in mice subjected to repeated restraint ( P < 0.01) and from 552 ± 98 to 314 ± 58 ng/ml ( P < 0.001) in males and females, respectively. Male UCN1-KO mice did not show any adaptation to repeated restraint; instead, restraint-stimulated corticosterone levels were increased from 274 ± 80 ng/ml in naïve animals to 480 ± 75 ng/ml in mice subjected to repeated restraint ( P < 0.001). Female UCN1-KO mice showed only a partial adaptation to repeated restraint, with a decrease in the restraint-stimulated corticosterone response from 631 ± 102 ng/ml in naïve animals to 467 ± 78 ng/ml in mice subjected to repeated restraint ( P < 0.01). In addition, UCN1-KO mice showed no corticosterone response to 2-h cold environment. These data demonstrate an important role for UCN1 in the HPA axis adaptation to repeated restraint and in the corticosterone response to a cold environment.