[Comparison of effects of electroacupuncture at "Tianshu" (ST25) and "Dachangshu" (BL25) on intestinal sensitivity and expression of muscarinic MR and 5-HTR in irritable bowel syndrome rats].

Objective: To observe and compare the effect of electroacupuncture (EA) of "Tianshu" (ST25) and "Dachangshu" (BL25) on intestinal sensitivity and the expression of M muscarinic acetylcholine receptor (MR) and 5-hydroxytryptamine 3A receptor (5-HTR) in the colon tissue in irritable bowel syndrome (IBS) rats, so as to explore its mechanism underlying improvement of IBS.

Methods: Forty newborn Wistar rats were randomly divided into blank control, model, ST25 and BL25 groups (＝10 rats per group). The IBS model was established by joint application of maternal separation, acetic acid enema plus colorectal distension from day 8 to 21 after birth. At the age of 9 weeks, EA (2 Hz/100 Hz, 0.1－0.3 mA) was applied to ST25 and BL25 for 20 min, once every other day for 5 times. The modified method was used to record the abdominal withdrawal reflex (AWR), so as to evaluate the visceral sensitivity by referring to the modified Al-Chaer's and colleagues' methods. The threshold (initial wave), the number and peak-peak value of contraction waves (AWR) within 90 s were recorded. The immunoactivity of MR and 5-HTR in the colon tissue was detected by immunohistochemistry.

Results: After modeling, the latency was obviously shortened, the number and peak-peak values of contraction waves of intestine were significantly increased, and the immunoactivity of MR and 5-HTR was notably up-regulated in the model group compared with the blank control group (<0.01). After the EA intervention, the latency was obviously prolonged, the peak-peak value in both ST25 and BL25 groups, and the number of contraction waves in the ST25 group were significantly decreased (<0.01), and the expression levels of M and 5-HT R were considerably down-regulated in both ST25 and BL25 groups relevant to the model group (<0.01). The therapeutic effects were significantly better in the ST25 group than in the BL25 group in prolonging the latency and reducing the contraction wave number, and in down-regulating the expression of colonic MR and 5-HTR (<0.05, <0.01).

Conclusion: EA at ST25 and BL25 can reduce the intestinal sensitivity in IBS rats, which is probably associated with its effects in down-regulating the expression of MR and 5-HTR in the colon. The therapeutic effects of ST25 were obviously better than those of BL25 in suppressing intestinal sensitivity and expression of colonic MR and 5-HTR.