Electroacupuncture at ST36 Alleviates Visceral Hypersensitivity and Anxiety via ACC-AIC Circuit Modulation in IBS Rats.

PURPOSE: This study aimed to explore the effects of Electroacupuncture (EA) at the Zusanli (ST36) point on Irritable Bowel Syndrome (IBS), along with its associated visceral hypersensitivity and anxiety-like behaviors. METHODS: To establish the IBS rat model, Water Avoidance Stress (WAS) was used. After successful modeling, rats were randomly divided into four groups: Normal group, IBS group, ST36 group, and Sham EA group. The ST36 group received EA at bilateral ST36 acupoints, while the Sham EA group underwent identical procedures without electrical stimulation. Visceral hypersensitivity was assessed using abdominal withdrawal reflex (AWR) scores, and anxiety-like behaviors were evaluated through open field test and elevated plus maze. Neuronal activation was measured via c-Fos expression, and multi-channel electrophysiological recordings from the anterior cingulate cortex (ACC) and anterior insular cortex (AIC) regions were analyzed for neural activity patterns. Autonomic nervous function was assessed through heart rate variability analysis. RESULTS: EA at ST36 acupoint effectively alleviated visceral hypersensitivity and anxiety-like behaviors in IBS rats. The treatment normalized abnormal neural activity and local field potential (LFP) oscillations in the ACC and AIC regions. Specifically, EA corrected the pathologically increased firing rates and irregular discharge patterns in both neuronal types within these brain regions. Furthermore, EA reduced the pathologically enhanced synchronization between ACC and AIC in delta (0.5-3 Hz) and theta (3-8 Hz) frequency bands. EA also ameliorated autonomic nervous dysfunction associated with IBS manifestations. CONCLUSION: These findings indicate that EA at ST36 acupoint modulates neuronal activity in the ACC and AIC regions, thereby alleviating visceral hypersensitivity and anxiety-like behaviors in IBS rats, and improving autonomic nervous function.