The PVN Astrocyte-Excitatory Neuron Functional Axis Mediates Chronic Stress-Induced Depressive-Like Behaviors

Major depressive disorder (MDD) is a common psychiatric disorder, and accumulating evidence suggests that astrocytes play an important role in the regulation of emotional behaviors. However, the mechanisms by which astrocytes in the hypothalamic paraventricular nucleus (PVN) contribute to chronic stress-induced depression remain unclear. In this study, a chronic restraint stress (CRS) mouse model was established, and depressive-like behaviors were assessed using the sucrose preference test, open field test, tail suspension test, and forced swim test. Immunofluorescence staining, chemogenetic manipulation, fiber photometry, transcriptomic analysis, and quantitative real-time PCR were employed to investigate the role of PVN astrocytes and their interactions with excitatory neurons. CRS induced robust depressive-like behaviors and was accompanied by reactive astrocyte activation in the PVN, as evidenced by increased GFAP expression and morphological remodeling. Fiber photometry recordings revealed enhanced astrocytic calcium activity under both basal and stress-related behavioral conditions following CRS exposure. Chemogenetic activation of PVN astrocytes induced depressive-like behaviors in naïve mice, whereas inhibition of astrocytic activity alleviated depressive-like behaviors in CRS mice. Moreover, CRS increased c-Fos expression and calcium activity in CaMKIIα-positive excitatory neurons within the PVN. Bidirectional modulation of astrocyte activity correspondingly altered excitatory neuronal activity, indicating a functional coupling between these cell populations. Transcriptomic screening combined with qPCR validation further identified upregulated expression of the stress-responsive genes Timp4 and Manf in the PVN following CRS. Collectively, these findings demonstrate that PVN astrocytes are critical regulators of chronic stress-induced depressive-like behaviors and suggest that the PVN astrocyte-excitatory neuron functional axis represents a potential therapeutic target for depression.