Acupuncture at heterotopic acupoints enhances jejunal motility in constipated and diarrheic rats.

AIM To investigate the effect and mechanism of acupuncture at heterotopic acupoints on jejunal motility, particularly in pathological conditions. METHODS Jejunal motility was assessed using a manometric balloon placed in the jejunum approximately 18-20 cm downstream from the pylorus and filled with approximately 0.1 mL warm water in anesthetized normal rats or rats with diarrhea or constipation. The heterotopic acupoints including LI11 (Quchi), ST37 (Shangjuxu), BL25 (Dachangshu), and the homotopic acupoint ST25 (Tianshu), and were stimulated for 60 s by rotating acupuncture needles right and left at a frequency of 2 Hz. To determine the type of afferent fibers mediating the regulation of jejunal motility by manual acupuncture, the ipsilateral sciatic A or C fibers of ST37 were inactivated by local application of the A-fiber selective demyelination agent cobra venom or the C fiber blocker capsaicin. Methoctramine, a selective M2 receptor antagonist, was injected intravenously to identify a specific role for M2 receptors in mediating the effect of acupuncture on jejunal motility. RESULTS Acupuncture at heterotopic acupoints, such as LI11 and ST37, increased jejunal motility not only in normal rats, but also in rats with constipation or diarrhea. In normal rats, manual acupuncture at LI11 or ST37 enhanced jejunal pressure from 7.34 ± 0.19 cmH2O to 7.93 ± 0.20 cmH2O, an increase of 9.05% ± 0.82% (P < 0.05), and from 6.95 ± 0.14 cmH2O to 8.97 ± 0.22 cmH2O, a significant increase of 27.44% ± 1.96% (P < 0.01), respectively. In constipated rats, manual acupuncture at LI11 or ST37 increased intrajejunal pressure from 8.17 ± 0.31 cmH2O to 9.86 ± 0.36 cmH2O, an increase of 20.69% ± 2.10% (P < 0.05), and from 8.82 ± 0.28 cmH2O to 10.83 ± 0.28 cmH2O, an increase of 22.81% ± 1.46% (P < 0.05), respectively. In rats with diarrhea, MA at LI11 or ST37 increased intrajejunal pressure from 11.95 ± 0.35 cmH2O to 13.96 ± 0.39 cmH2O, an increase of 16.82% ± 2.35% (P < 0.05), and tended to increase intrajejunal pressure (from 12.42 ± 0.38 cmH2O to 13.05 ± 0.38 cmH2O, an increase of 5.07% ± 1.08%, P > 0.05), respectively. In contrast, acupuncture ST25, a homotopic acupoint, decreased not only intrajejunal pressure, but also significantly decreased frequency in normal rats and rats with constipation or diarrhea. Following demyelination of Aδ fibers, acupuncture at ST37 again augmented intrajejunal pressure to 121.48% ± 3.06% of baseline. Following capsaicin application for 24 h, acupuncture at ipsilateral ST37 increased intrajejunal pressure significantly to 106.63% ± 1.26% of basal levels when compared to measurements prior to capsaicin treatment (P < 0.05). Acupuncture at LI11, ST37, or BL25 significantly rescued methoctramine-mediated inhibition of jejunal motility amplitude from 42.83% ± 1.65% to 53.43% ± 1.95% of baseline (P < 0.05), from 45.15% ± 2.22% to 70.51% ± 2.34% of baseline (P < 0.01), and from 38.03% ± 2.34% to 70.12% ± 2.22% of baseline (P < 0.01), respectively. CONCLUSION Acupuncture at heterotopic acupoints increases the amplitude of jejunal motility in rats. C fibers and M2 receptors predominantly and partially mediate the regulation of jejunal motility by acupuncture, respectively.