Electroacupuncture relieves neuropathic pain-induced anxio-depression-like behaviors by regulating glutamatergic neurons in the ventrolateral orbital cortex of mice

To investigate whether electroacupuncture (EA) at “Yanglingquan” (GV34) and “Xuanzhong” (GB34) can alleviate anxio-depression-like behaviors induced by neuropathic pain and whether the effect of EA is in connection with the activity of glutamatergic neurons in the ventrolateral orbital cortex (VLO).

The neuropathic pain model was established by common peroneal nerve ligation (CPNL). GV34 and GB34 were selected in EA treatment (2 Hz/15 Hz, 1 mA), 15 min each time, once a day for 7 d. Chemogenetic mixture viruses rAAV-VGLUT1-CRE-WPREs and rAAV-Ef1a-DIO-hM3Dq-mCherry-WPREs or rAAV-Ef1a-DIO-hM4Di-mCherry-WPREs were injected into the VLO, respectively. Clozapine-N-oxide (CNO) was injected intraperitoneally to regulate the activity of glutamatergic neurons in the VLO precisely. Mechanical withdrawal threshold (MWT) and paw withdrawal latency (PWL) were measured by dynamic plantar tactile instruments and plantar thermal nociceptor instruments. Anxiodepression-like behaviors were measured by behavioral tests, including open field test, elevated plus maze test, forced swimming test, and tail suspension test. The activation and inhibition levels of neurons were observed by immunofluorescence staining.

Compared with the sham group, the MWT and PWL of CPNL mice were significantly decreased (P<0.001) on the 3^rd day after surgery and lasted until the 28^th day. After CPNL, the activity time spent in the central area of open field test reduced (P<0.001), the percentage of entries and activity time in the open arm of elevated plus maze test were significantly reduced (P<0.001, P<0.05) ；the immobile duration of forced swimming test and tail suspension test were remarkably prolonged (P<0.01, P<0.05) of mice in the CPNL group. However, after EA treatment, compared with the CPNL group, the anxio-depression-like behaviors of the mice were alleviated (P<0.05, P<0.01, P<0.001). Activating glutamatergic neurons of VLO produced an anti-anxio-depression effect (P<0.05, P<0.01) in neuropathic pain mice. Compared with the inhibited+EA+saline group, inhibiting glutamatergic neurons of VLO reversed (P<0.001, P<0.01, P<0.05) the effect of EA.

EA at GV34 and GB34 can alleviate anxio-depression-like behaviors induced by neuropathic pain through the modulation of glutamatergic neuron activity in the VLO.