Electro‐acupuncture at ST37 and ST25 induce different effects on colonic motility via the enteric nervous system by affecting excitatory and inhibitory neurons

Abstract Background On the basis of the importance of the enteric nervous system ( ENS ) in gastrointestinal motility, we hypothesized that the ENS may mediate the therapeutic efficacy of electro‐acupuncture ( EA ) in constipation by regulating the mechanisms underlying the effects of EA on gastrointestinal function. Methods Model mice with constipation were generated by gastric instillation of 0‐4°C normal saline. Defecation time and stool (form and wet and dry weight) were assessed. The effect of EA at ST 37 or ST 25 on colorectal motility and proximal colonic motility was assessed using a water‐filled balloon. The expression of protein gene product 9.5 ( PGP 9.5), the cholinergic neuron marker acetyltransferase (Ch AT ) and the anticholinergic neuron marker nitric oxide synthase ( nNOS ) was detected by immunohistochemistry, real‐time quantitative polymerase chain reaction ( qPCR ) and western blot analysis. Key Results ST 37 and ST 25 improved colorectal pressure; however, ST 37 but not ST 25 improved proximal colonic pressure. In the proximal colon, the expression of PGP 9.5 returned to normal after EA at ST 37, while EA at ST 25 did not have this effect. In addition, qPCR and western blot analysis showed that ST 37 could downregulate the expression of nNOS and upregulate the expression of Ch AT to normal levels, while ST 25 could only downregulate the expression of nNOS to normal levels. Conclusions and Inferences Electro‐acupuncture at specific acupoints can improve intestinal motility in constipation by altering the ENS and differentially affecting excitatory and inhibitory neurons, restoring the coordination between contraction and relaxation muscles, and working in concert with the central nervous system and peripheral neural pathways.