PSD-93 up-regulates the synaptic activity of corticotropin-releasing hormone neurons in the paraventricular nucleus in depression

Since the discovery of ketamine anti-depressant effects in last decade, it has effectively revitalized interest in investigating excitatory synapses hypothesis in the pathogenesis of depression. In the present study, we aimed to reveal the excitatory synaptic regulation of corticotropin-releasing hormone (CRH) neuron in the hypothalamus, which is the driving force in hypothalamic-pituitary-adrenal (HPA) axis regulation. This study constitutes the first observation of an increased density of PSD-93-CRH co-localized neurons in the hypothalamic paraventricular nucleus (PVN) of patients with major depression. PSD-93 overexpression in CRH neurons in the PVN induced depression-like behaviors in mice, accompanied by increased serum corticosterone level. PSD-93 knockdown relieved the depression-like phenotypes in a lipopolysaccharide (LPS)-induced depression model. Electrophysiological data showed that PSD-93 overexpression increased CRH neurons synaptic activity, while PSD-93 knockdown decreased CRH neurons synaptic activity. Furthermore, we found that LPS induced increased the release of glutamate from microglia to CRH neurons resulted in depression-like behaviors using fiber photometry recordings. Together, these results show that PSD-93 is involved in the pathogenesis of depression via increasing the synaptic activity of CRH neurons in the PVN, leading to the hyperactivity of the HPA axis that underlies depression-like behaviors.