Objective To observe the effect of acupuncture of “Tianshu”(ST25) at different depths on colonic transportation function

expressions of colonic substance P(SP) and interstitial cells of Cajal(ICC) in rats with slow transit constipation(STC)

so as to explore its mechanisms underlying improvement of STC.Methods Fifty male Wistar rats were selected and randomly divided into control

STC model

conventional acupuncture

deep needling group 1 and deep needling group 2 groups

with 10 rats in each group.The STC model was established by gavage of 1 mg/mL compound diphenoxylate suspension(10 mg/kg)

once every other day for 21 days

and rats of the control group were given the same dose of distilled water by gavage.EA(2 Hz

2 mA) was applied to “Tianshu”(ST25)

with the acupuncture needle inserted to a depth of 3 mm for rats of the conventional acupuncture group

4.5 mm for those of deep needling group 1

and 10 mm for those of the deep needling group 2. The acupuncture needle was twirled for 1 min

then retained for 15 min each time

once a day for 15 consecutive days.Following modeling

rats of the 4 groups and the control group received gavage of active carbon 2 mL(100 g/L) for observing the excretion time of the first black stool grain to assess the intestinal transit function. The colonic myoelectric activities(frequency and amplitude) were recorded by using BIOPAC multichannel physiograph. The immunoactivity of SP and c-kit(a transmembrane protein kinase for identification of ICC) of colonic musculature was detected by immunohistochemistry. Results Compared with the control group

the time of excretion of the first black stool grain

and the amplitude of colonic electromyogram(EMG) were significantly increased(P<0.01)

while the frequency of EMG

expressions of SP and c-kit(ICC) were significantly decreased in the model group(P<0.01). In contrast to the model group

both deep needling group 1 and 2 had a decrease in the time of excretion of the first black stool grain

and amplitude of intestinal EMG

and an increase of frequency of intestinal EMG

and immunoactivity of SP and c-kit(P<0.01). The effect of deep needling 2 is superior to that of deep needling 1 in reducing the time of excretion of the first black stool grain(P<0.05)

lowering the amplitude of EMG of the gut smooth muscle(P<0.05) and in increasing the frequency of EMG(P<0.05) and the expressions of SP and c-kit(P<0.05). No significant changes were found in the levels of frequency and amplitude of EMG

and expressions of SP and c-kit after routine needling in comparison with the model group(P>0.05)

except the excretion time of the first black stool grain(P<0.05). Conclusion Deep needling at ST25 at depth of 4.5 mm and 10 mm

especially at depth of 10 mm

has a significant effect in promoting gut motility to ameliorate constipation in rats with STC

which may be related to its function in up-regulating the expressions of SP and ICC activity.