Activation of the HPA is a feature of the neurobiology of depression; elevated concentrations of CRH have been found in the cerebrospinal fluid of depressed patients42 and the PVN of the hypothalamus has been shown to contain increased numbers of CRH containing neurons.43 In our study, we found increased expression of CRH in the PVN region of the hypothalamus in OBx mice. Here, CRH is linked to major depressive disorder.