Astrocytes in the Ventral Hippocampus Bidirectionally Regulate Innate and Stress‐Induced Anxiety‐Like Behaviors in Male Mice

The mechanisms of anxiety disorders, the most common mental illness, remain incompletely characterized. The ventral hippocampus (vHPC) is critical for the expression of anxiety. However, current studies primarily focus on vHPC neurons, leaving the role for vHPC astrocytes in anxiety largely unexplored. Here, genetically encoded Ca2+ indicator GCaMP6m and in vivo fiber photometry calcium imaging are used to label vHPC astrocytes and monitor their activity, respectively, genetic and chemogenetic approaches to inhibit and activate vHPC astrocytes, respectively, patch‐clamp recordings to measure glutamate currents, and behavioral assays to assess anxiety‐like behaviors. It is found that vHPC astrocytic activity is increased in anxiogenic environments and by 3‐d subacute restraint stress (SRS), a well‐validated mouse model of anxiety disorders. Genetic inhibition of vHPC astrocytes exerts anxiolytic effects on both innate and SRS‐induced anxiety‐related behaviors, whereas hM3Dq‐mediated chemogenetic or SRS‐induced activation of vHPC astrocytes enhances anxiety‐like behaviors, which are reversed by intra‐vHPC application of the ionotropic glutamate N‐methyl‐d‐aspartate receptor antagonists. Furthermore, intra‐vHPC or systemic application of the N‐methyl‐d‐aspartate receptor antagonist memantine, a U.S. FDA‐approved drug for Alzheimer's disease, fully rescues SRS‐induced anxiety‐like behaviors. The findings highlight vHPC astrocytes as critical regulators of stress and anxiety and as potential therapeutic targets for anxiety and anxiety‐related disorders. Astrocytes in the ventral hippocampus (vHPC) display increased intracellular calcium levels in response to stress stimuli, leading to an ambient glutamate excess and enhanced anxiety behaviors. Disruption or enhancement of vHPC astrocytic calcium signals decreases or increases anxiety, respectively. In an anxiety mouse model, intra‐vHPC or systemic application of antagonists for the ionotropic glutamate N‐methyl‐d‐aspartate receptors rescues anxiety behaviors.