Objective To observe and compare the effect of electroacupuncture(EA)of"Tianshu"(ST25)and"Dachangshu"(BL25)on intestinal sensitivity and the expression of M3 muscarinic acetylcholine receptor(M_(3R))and5-hydroxytryptamine 3 Areceptor(5-HT_(3A)R)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(n=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 swere recorded.The immunoactivity of M_(3R) and 5-HT_(3A)R 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 M_(3R) and 5-HT_(3A)R was notably up-regulated in the model group compared with the blank control group(P<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(P<0.01)

and the expression levels of M3 and 5-HT_(3A)R were considerably down-regulated in both ST25 and BL25 groups relevant to the model group(P<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 M_(3R) and 5-HT_(3A)R(P<0.05

P<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 M_(3R) and 5-HT_(3A)R in the colon.The therapeutic effects of ST25 were obviously better than those of BL25 in suppressing intestinal sensitivity and expression of colonic M_(3R) and 5-HT_(3A)R.