Effects of electroacupuncture at auricular points on excitability of glutamatergic neurons in the anterior cingulate cortex of posttraumatic stress disorder mice

To elucidate the relationship between the auricular point stimulation and the activity of glutamatergic neurons in the anterior cingulate cortex (ACC) from the perspective of intrinsic excitability plasticity of neurons in mice with posttraumatic stress disorder (PTSD), so as to explore the underlying mechanisms of acupuncture at auricular points in improving emotional diseases induced by PTSD.

C57BL/6J male mice were randomly divided into control, PTSD model, sham electroacupuncture (EA), and EA groups, with 5 mice in each group. The glutamatergic neurons were labelled by injection of AAV2/9-CaMK Ⅱ α-EGFP viral fluid into the bilateral ACC. Fourteen days after the injection, the PTSD model was established by single prolonged stress (restraint stress, forced swimming, ether exposure) and plantar electrical shock. EA (2 Hz/15 Hz, 1 mA) was applied to bilateral "Xin" points and the center of auriculae of auricular concha area for 30 min, once daily for 7 days. Mice of the sham EA group were anesthetized for 30 min per day for 7 days, but no EA treatments were given. The anxiety-like behavior of mice was evaluated by open field (OF) and elevated plus maze (EPM) tests after 2 weeks of modeling. The whole-cell patchclamp method was used to record the intrinsic excitability level of ACC glutamatergic neurons.

Compared with the control group, the dwell time and locomotor distance in the central area of the OF, the dwell time and entry times percentage in the open arms of the EPM in the model group were significantly reduced (P < 0.001, P < 0.01). At the same time, the intrinsic excitability of ACC glutamatergic neurons in model mice was suppressed, presenting as enhanced rheobase currents (P < 0.01) and decreased spike number (P < 0.05, P < 0.01, P < 0.001). Compared with the model group, the dwell time and locomotor distance in the central area of the OF, the dwell time and entry times percentage in the open arms of the elevated plus maze were significantly increased (P < 0.001, P < 0.01), and the intrinsic excitability of ACC glutamatergic neurons was significantly improved, presenting as reduced rheobase currents (P < 0.05) and an increased spike number (P < 0.05) in the EA group. Compared with the sham EA group, the dwell time and locomotor distance in the central area of the OF, the dwell time and entry times percentage in the open arms of the EPM were significantly increased (P < 0.001, P < 0.01) in the EA group, and the intrinsic excitability of ACC glutamatergic neurons was significantly improved, presenting as reduced rheobase currents (P < 0.01) and an increased spike number (P < 0.05).

EA of auricular points can effectively alleviate the anxiety-like behavior of PTSD mice and increase the intrinsic excitability level of glutamatergic neurons in ACC, which may be one of the neural mechanisms of auricular point stimulation in the treatment of emotional diseases.