[Effects of electroacupuncture at "Zhongliao" and "Xialiao" on serotonin signaling system and short-chain fatty acids in slow transit constipation rats].

Objective: To observe the effect of electroacupuncture (EA) at "Zhongliao" (BL33) and "Xialiao" (BL34) on the 5-hydroxytryptamine (5-HT) signaling system in colon tissue and short-chain fatty acids in feces of rats with slow transit constipation (STC), so as to explore the underlying mechanisms of EA in the treatment of STC.

Methods: A total of 32 SD rats were randomly divided into normal, model, drug control and EA groups, with 8 rats in each group. The STC model was established by intragastric administration of loperamide for 14 days. The EA stimulation (2 Hz/15 Hz) was performed at bilateral BL33 and BL34 for 30 min, once a day for 14 days. The first black stool de-fecation time and fecal water content were detected after treatment. The expressions of 5-hydroxytryptamine 4 receptor (5-HT4R), tryptophan hydroxylase 1 (TPH1) and 5-HT transporter (SERT) in colon tissues were detected by Western blot. The contents of substance P (SP) and vasoactive intestinal peptide (VIP) in serum were detected by ELISA. The contents of 5-HT in colon tissue and short chain fatty acid (SCFA) in feces were detected by mass spectrometry.

Results: Compared with the normal group, the fecal water content, the expressions of 5-HT, 5-HT4R, TPH1 and SERT in colon tissue, the content of serum SP were significantly decreased (<0.05), the first black stool de-fecation time, and the content of serum VIP was significantly increased (<0.05), the contents of SCFA in feces were significantly decreased except isobutyric acid (<0.05) in the model group. Compared with the model group, the fecal water content, the expressions of 5-HT, 5-HT4R, TPH1 and SERT in colon tissues, the contents of acetic acid and butyrate in feces were significantly increased (<0.05) in the EA and drug control groups, the first black stool defecation time was decreased (<0.05) in the EA and drug control groups, and the content of serum SP was increased and the content of serum VIP was decreased (<0.05) in the EA group. Compared with the drug control group, the content of serum VIP was significantly decreased (<0.05), and the expressions of TPH1 and SERT in colon tissue were significantly increased (<0.05) in the EA group.

Conclusion: EA at BL33 and BL34 can promote intestinal motility by intervening multiple links of 5-HT signaling system in treating STC.