Electroacupuncture Alleviates Pain and Anxiety in CFA-Induced Mice by Suppressing Glutamatergic Neurons in the Spinoparabrachial Pathway.

The spinoparabrachial tract is a major ascending pathway that transmits nociceptive signals from the spinal cord to the brain, but whether electroacupuncture (EA) relieves pain-anxiety comorbidity by modulating this pathway remains unclear. Here, we investigated the effects of EA on mechanical allodynia and anxiety-like behaviors in Complete Freund's adjuvant (CFA)-induced inflammatory pain mice using von Frey testing, the open field test, and the elevated plus maze, combined with chemogenetic manipulation of glutamatergic projections from the spinal dorsal horn (SDH) to the lateral parabrachial nucleus (LPBN). EA attenuated CFA-induced mechanical allodynia and anxiety-like behaviors and reduced c-Fos expression in both the SDH and LPBN. Chemogenetic inhibition of LPBN glutamatergic neurons mimicked the analgesic and anxiolytic effects of EA, whereas their activation abolished these effects. Activation of either ipsilateral or contralateral SDH→LPBN glutamatergic projections induced pain- and anxiety-like phenotypes that depended on intact LPBN glutamatergic output. Moreover, selective activation of spinoparabrachial glutamatergic terminals was sufficient to block the therapeutic efficacy of EA. These findings indicate that EA alleviates CFA-induced pain-anxiety comorbidity by inhibiting the SDH-LPBN glutamatergic circuit, identifying a key ascending pathway through which peripheral EA signals modulate central pain and affective processing.