Effects of electroacupuncture of different frequencies on SP and VIP expression levels in colon of rats with slow transit constipation

Abstract

To observe the effects of electroacupuncture (EA) of different frequencies on the expression levels of substance P (SP) and vasoactive intestinal peptide (VIP) in the colon of rats with slow transit constipation (STC). One hundred healthy male Sprague-Dawley (SD) rats were randomly divided into a normal group, a model group, a low-frequency EA group, a high-frequency EA group and a variable-frequency EA group, with 20 rats in each group. The rats in the normal group were fed with normal diet. The rats in the other groups were fed with phenethylpiperidine in the diet at a dose of 8 mg/(kg·bw) per day, for 120 d, to establish the STC model. Rats in the normal group and the model group did not receive any treatment; rats in the low-frequency EA group were treated with 2 Hz continuous wave EA, rats in the high-frequency EA group were treated with 100 Hz continuous wave EA, and rats in the variable-frequency EA group were treated with 2 Hz/100 Hz sparse-dense EA. The current intensity of the EA was determined by the slight vibration of the rat limbs without painful screaming. The intervention was performed once a day, 15 min/time for continuous 15 d. After treatment, the intestinal transit function and the expression levels of SP and VIP in the colon of the rats in each group were determined. After treatment, the defecation duration of the first dark stool in the model group was significantly longer than that in the normal group (P<0.05); the defecation durations of the first dark stool in the low-frequency EA group, high-frequency EA group and variable-frequency EA group were significantly shorter than the duration in the model group (all P<0.05); compared with the low-frequency EA group, the first dark stool defecation duration of rats in the variable-frequency EA group was significantly shorter (P<0.05); compared with the normal group, the SP and VIP expression levels in the colon of the model group were significantly decreased (both P<0.01); the SP and VIP expression levels in the colon of the low-frequency EA group, the high-frequency EA group and the variable-frequency EA group were significantly higher than those in the model group (all P<0.05); compared with the high-frequency EA group, the SP expression levels in the colon in the low-frequency EA group and the variable-frequency EA group were significantly increased (both P<0.05); compared with the low-frequency EA group, the VIP expression levels in the colon in the high-frequency EA group and the variable-frequency EA group were significantly increased (both P<0.05). EA improves the intestinal function of STC model rats by regulating the expression levels of SP and VIP in rat colon. The EA stimulation with 100 Hz continuous wave, 2 Hz/100 Hz sparse-dense wave shows a better improvement in the colonic transit function in STC rats, followed by 2 Hz continuous wave.