CRF₁ but not glucocorticoid receptor antagonists reduce separation-induced distress vocalizations in guinea pig pups and CRF overexpressing mouse pups. A combination study with paroxetine

Rationale Given the large number of patients that does not respond sufficiently to currently available treatment for anxiety disorders, there is a need for improved treatment. Objectives We evaluated the anxiolytic effects of corticotropin releasing factor (CRF)₁ receptor antagonists and glucocorticoid receptor (GR) antagonists in the separation-induced vocalization test in guinea pigs and transgenic mice with central CRF overexpression. Furthermore, we explored effects of these drugs when given in combination with a suboptimal dose of a selective serotonin re-uptake inhibitor (SSRI). Methods In guinea pig pups, the CRF₁ receptor antagonists CP-154,526 and DMP695, and the GR antagonists mifepristone and Org34517 (all at 2.5, 10 and 40 mg/kg intraperitoneally (IP)) were tested alone or in combination with 0.63 mg/kg paroxetine IP. In CRF overexpressing mouse pups and wild type littermates, effects of CP-154,526 (10, 20 and 40 mg/kg subcutaneously (SC)) and mifepristone (5, 15, 45 mg/kg SC) were studied alone or in combination with 0.03 mg/kg paroxetine SC. Results CRF₁ but not GR antagonists reduced the number of calls relative to vehicle in guinea pigs and mice, independent of genotype. Treatment of CRF₁ receptor or GR antagonists with paroxetine had no combined effect in guinea pigs, wild type or CRF overexpressing mice. Conclusions Current results indicate robust anxiolytic properties of CRF₁ receptor antagonists in guinea pigs and mice overexpressing CRF, and lack thereof of GR antagonists. Although no combined treatment effects were observed, it would be interesting to study combined treatment of CRF₁ receptor antagonists with SSRIs following chronic drug administration.