Hyperactivity of CRH neuronal circuits as a target for therapeutic interventions in affective disorders.

Increasing evidence suggests that the neuroendocrine changes seen in psychiatric patients, especially in those suffering from affective disorders, may be causally related to the psychopathology and course of these clinical conditions. The most robustly confirmed neuroendocrine finding among psychiatric patients with affective disorders is hyperactivity of the hypothalamic-pituitary-adrenocortical (HPA) system, resulting from hyperactive hypothalamic corticotropin-releasing hormone (CRH) neurons. A large body of preclinical and clinical evidence suggests that both genetic and environmental factors contribute to the development of these HPA system abnormalities. Further, normalization of HPA system regulation was shown to be a prerequisite for favorable treatment response and stable remission among depressives. Preclinical data based on animal models including selectively bred rat lines and mouse mutants support the notion that CRH neurons are hyperactive also in neuroanatomical regions that are involved in behavioral regulation but are located outside the neuroendocrine system. This raises the question of whether more direct interventions such as CRH receptor antagonists would open a new lead in the treatment of stress-related disorders such as depression, anxiety and sleep disorders. Recent clinical observations support this possibility.