Effects of Electroacupuncture at ST36 on Visceral Pain and Inflammatory Markers in IBS Rats.

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by recurrent visceral pain associated with low-grade gut inflammation. Electroacupuncture (EA) at acupoint ST36 (Zusanli) is reputed to alleviate gastrointestinal disorders, but its effects on IBS-related visceral hypersensitivity and inflammation remain to be fully elucidated. This study evaluated whether EA at ST36 attenuates visceral pain and modulates key inflammatory mediators in the IBS rat model.

METHODS

Forty male rats were randomly assigned to Control, IBS model, IBS + EA, and IBS + Sham groups (n = 10 each). IBS was induced by intracolonic acetic acid enema combined with daily restraint stress for 1 week, validating the IBS-D model. EA was applied at bilateral ST36 (2/100 Hz alternating frequency, ~0.5 mA, 20 min) every other day for 2 weeks; sham treatment used superficial needling with no electrical current. Visceral pain was assessed by abdominal withdrawal reflex (AWR) scores and electromyographic responses to graded colorectal distension. Colonic tissues were analyzed for pro-inflammatory cytokines (interleukin-1β, IL-6, tumor necrosis factor-α) by ELISA and for the expression of pain or inflammation-related proteins (TRPV1 and nuclear factor kappa B, NF-κB) by Western blot analyses.

RESULTS

IBS model rats exhibited pronounced visceral hypersensitivity, with AWR scores significantly elevated (e.g., score 3 threshold volume reduced by ~40% vs. controls, p < 0.01). EA at ST36 markedly alleviated visceral pain, increasing pain threshold and reducing AWR scores by ~30%-50% compared to untreated IBS (p < 0.05). EA also significantly downregulated colonic IL-1β, IL-6, and TNF-α levels (by 45%-60% vs. IBS, p < 0.01) and reduced TRPV1 and NF-κB expression toward normal levels.

CONCLUSION

EA at ST36 produced significant analgesic and anti-inflammatory effects in IBS model rats. Visceral hypersensitivity was blunted and colonic inflammatory biomarkers (cytokines, TRPV1, NF-κB) were suppressed by EA, suggesting that EA at ST36 modulates neuro-immune pathways to relieve IBS-related pain. These findings support the therapeutic potential of ST36-targeted electroacupuncture for managing IBS visceral pain via inflammatory mechanism attenuation.