Up-regulation of GluR1 in paraventricular nucleus and greater expressions of synapse related proteins in the hypothalamus of chronic unpredictable stress-induced depressive rats.

Converging evidence indicates that abnormal glutamatergic and synaptic systems may be associated with the pathophysiology of depression. Over-activation of corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN) plays a key role in the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and is a prominent feature in depression. In this study, we examined the effect of chronic unpredictable stress (CUS) in rats on the expression of AMPA subunit GluR1 protein in the hypothalamic PVN as well as on the expression of GluR1 and several synapse-related proteins in the hypothalamus. We found that CUS in rats induced CRH over-expression accompanied by significant GluR1 up-regulation in the hypothalamic PVN and GluR1 co-localized with CRH in the PVN area. The expression of GluR1 and three synapse-related proteins (PSD95, SYP and MAP2) in the hypothalamus were also increased at both mRNA and protein levels in CUS rats. Correlation analysis showed that the levels of the above proteins are directly correlated with depression-like behaviors of rats in sucrose preference test, open field test and forced swim test. These findings suggest that the augmented glutamatergic and synaptic signaling might be a potential mechanism underlying CRH over-activation in the hypothalamic PVN and contribute to CUS-induced depression-like behaviors in rats.