Effect of inescapable stress in rodent models of depression and posttraumatic stress disorder on CRH and vasopressin immunoreactivity in the hypothalamic paraventricular nucleus.

The present study was designed to reveal possible common and specific neuroendocrine mechanisms of depression and anxiety-like states in rodents. Animal models of depression and anxiety (in particular, posttraumatic stress disorder, PTSD) were applied including the learned helplessness and the stress-restress paradigms, respectively. Immunocytochemical staining revealed that depressive- and anxiety-like states in animals were accompanied by the rise in corticotropin-releasing hormone (CRH) immunoreactivity in the parvocellular division of the hypothalamic paraventricular nucleus (PVN). Decrease in vasopressin-immunoreactivity in early period of depressive-like state development was followed by the normalization of vasopressin content in the hypothalamic PVN in delayed period. Increased CRH and vasopressin immunoreactivity in the magnocellular part of the PVN in delayed period of anxiety-like state development was detected only in the stress-restress paradigm. These results suggest that CRH hyperdrive in the parvocellular PVN appears to be a common neuroendocrine abnormality for depressive- and anxiety-like states in animals, while over-expression of CRH and vasopressin in the magnocellular PVN represents a specific feature of anxiety/PTSD-like state.