Abstract

Corticotropin-releasing factor 1 (CRF₁) receptor antagonists may represent a novel group of drugs for the pharmacotherapy of depression and/or anxiety disorders. We have investigated the behavioral, endocrine, and neurochemical effects of chronic administration of a selective CRF₁ receptor antagonist, CP-154,526. After 9 to 10 days of treatment with CP-154,526 (3.2 mg/kg/day), defensive withdrawal behavior was significantly decreased suggesting anxiolytic activity. In animals treated for 14 days with the low dose of CP-154,526, serum corticosterone concentrations returned to baseline levels faster after application of an airpuff startle. Using in situ hybridization, no changes in CRF₁ receptor mRNA expression were detected in parietal cortex, basolateral amygdala, or cerebellum after chronic treatment with CP-154,526. A dose-dependent decrease in CRF mRNA expression was observed in the hypothalamic paraventricular nucleus (PVN) and the Barrington's nucleus, an effect that was significant at the high but not the low dose of CP-154,526. CP-154,526 did not alter central CRF_2A receptor binding or mRNA expression, or urocortin mRNA expression. The present findings suggest that chronic administration of CP-154,526 produces anxiolytic-like effects but no evidence of adrenal insufficiency. Previous postmortem studies revealed increased CRF peptide and mRNA levels in the PVN of depressed patients, which may mediate the hyperactivity of the hypothalamic-pituitary-adrenal axis observed in such patients. In view of a possible use for CRF₁ receptor antagonists in the treatment of depression, the present finding that CP-154,526 decreases CRF synthesis in the PVN is of considerable interest.