Dynamic changes of media prefrontal cortex astrocytic activity in response to negative stimuli in male mice

Astrocytes play significant roles in regulating the central stress response. Chronic stress impairs the structure and function of astrocytes in many brain regions such as media prefrontal cortex (mPFC) in multiple neuropsychiatric conditions, but the astrocytic dynamics on the timescale of behavior remains unclear. Here, we recorded mPFC astrocytic activity in freely behaving mice and found that astrocytes are activated immediately by different aversive stimuli. Astrocyte specific GCaMP6s calcium indicator were virally expressed in mPFC astrocytes and fiber photometry experiments revealed that astrocytes are activated by tail-restraint (TRT), foot shock (FS), open arm exploration, stressor of height, predator odor and social defeat (SD) stress. ΔF/F analyses demonstrated that an unpredictable stimulus such as elevated platform stress (EPS) at the initial encounter induced the most intense and rapid changes in astrocytic calcium activity, while a predictable 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) stimulus resulted in the weakest response with a longer peak latency. In TRT, FS or SD test, a somatic stimulus led to higher average calcium activity level and faster average peak latency in repeated trails. Similar to TMT stimulus, astrocytic calcium activity in elevated plus maze (EPM) test exhibited a smaller average change in amplitude and the longest peak latency during open arm exploration. Moreover, astrocytic calcium activity exhibited different changes across behavioral states in SD tests. Our findings show that mPFC astrocytes exhibit distinct patterns of calcium activity in response to various negative stimuli, indicating that the dynamic activity of astrocytes may reflect the stress-related behavioral state under different stimulus conditions.