1000 Section - Kilohertz electrical stimulation alleviates neuropathic pain and anxiety co-morbidity by inhibiting CaMKII neuronal hyperactivation in the basolateral amygdala-anterior cingulate cortex pathway

Neuropathic pain and anxiety often co-occur, yet clinical non-invasive therapies for both are lacking. Kilohertz electrical stimulation (KHES) is used for analgesia, but its efficacy and central mechanism for the co-morbidity are unclear. This study aimed to assess if KHES can relieve nociceptive hypersensitivity and anxiety-like behaviors after nerve injury, and clarify its mechanism by inhibiting the overexcitation of CaMKII neurons in the basolateral amygdala to anterior cingulate cortex (BLA-ACC) pathway.

Design:

A chronic compression injury (CCI) mouse model was established. Starting from postoperative day 7, 18-kHz KHES (30 minutes daily, 6 days per week) was administered for three weeks. Behavioural assessments were conducted using the von Frey test to evaluate mechanical pain thresholds, open field test (OFT) and elevated plus maze test (EPMT) to assess anxiety levels. Immunofluorescence was used to identify the co-labeled neurons of c-Fos and CaMKII in the BLA and ACC. Retrograde viral tracing confirmed the BLA-ACC projections, and chemical genetics was applied to validate the necessity of these projections in the co-morbidity of neuropathic pain and anxiety.

Results:

KHES intervention significantly increased mechanical pain thresholds and alleviated anxiety-like behaviors in CCI mice. This was evidenced by a notable rise in pain threshold in the von Frey test,  and increased time spent in central regions and open arms during OFT and EPMT. Chemical genetics activation of the BLA-ACC pathway induced nociceptive hypersensitivity and anxiety-like behaviors in normal mice and reversed the analgesic and anxiolytic effects of KHES in CCI mice, validating the critical role of this pathway in the rehabilitation of pain-emotion co-morbidities.

Conclusion:

KHES alleviates neuropathic pain and anxiety co-morbidities by inhibiting the over-activation of CaMKII neurons in the BLA-ACC pathway. This study provides a non-invasive, targeted neuromodulation program for co-morbid neural circuits. It offers a new pathway and theoretical basis for clinical pain-anxiety co-morbidity rehabilitation strategies.