[Effect of electroacupuncture on E/I balance of prefrontal cortex and hippocampal pyramidal neurons in anxiety-like mice].

Objectives: To observe the effect of electroacupuncture (EA) on the excitatory/inhibitory (E/I) balance of prefrontal cortex and hippocampal pyramidal neurons in anxiety-like mice induced by chronic unpredictable mild stress (CUMS).

Methods: Forty-eight male C57BL/6 mice were randomly divided into control, control+EA (CE), model, and model+EA (ME) groups, with 12 mice in each group. The anxiety model was established by using CUMS (restraint, day-night reversal, forced swimming in warm water, food/water deprivation for 24 h, rearing in a humid environment, and shaking the cage) for 21 consecutive days. EA (2 Hz, 1 mA) was applied to "Baihui" (GV20) and "Yintang" (GV24⁺) for 30 min, once daily for 10 consecutive days. The anxiety-like behaviors of mice were evaluated by open field test and elevated plus maze (EPM) test. The E/I balance of the prefrontal cortex and hippocampal pyramidal neurons of the mice were observed by whole-cell recording.

Results: After modeling, the exploration time in the central area of open field test, the times of entries and residence time in the open arm of EPM test were significantly reduced (P<0.01) in the model group, while the spontaneous excitatory postsynaptic current (sEPSC) frequency, capacitance and E/I ratio of sEPSC in the dorsolateral prefrontal cortex (dlPFC), medial prefrontal cortex (mPFC) and ventral hippocampal CA1 (vCA1) were increased significantly (P<0.01). Compared with the model group, the exploration time in the central area of the open field, the times of entries and residence time in the open arm of EPM test were significantly increased (P<0.05, P<0.01), while the frequency, capacitance and E/I ratio of sEPSC in the dlPFC, mPFC and vCA1 were significantly decreased (P<0.01, P<0.05) in the ME group. In comparison with the CE group, the exploration time in the central area of the open field, the times of entries and residence time in the open arm of EPM test were significantly reduced (P<0.01), while the frequency, capacitance and E/I ratio of sEPSC in the dlPFC, mPFC and vCA1 were significantly increased (P<0.01, P<0.05) in the ME group.

Conclusions: Chronic stress may induce anxiety in mice by increasing the E/I of pyramidal neurons in dlPFC, mPFC and vCA1. EA may improve anxiety-like behaviors in mice by regulating the E/I balance of the above brain regions.