Effect characteristics of electroacupuncture at the acupoints of different regions in regulating gastric motility of the rats: response time.

OBJECTIVES: To observe the effect of electroacupuncture (EA) at "Zhongwan" (CV 12) and "Zusanli" (ST 36) on gastric motility and explore the response time of the acupoints at different regions for regulating gastric motility and its neuromechanism.

METHODS: Thirty-three SD rats were randomly divided into a normal group, a vagectomy group and a splanchnicotomy group, 11 rats in each one. Vagectomy and splanchnicotomy were operated in the rats of the vagectomy group and the splanchnicotomy group, respectively. In each group, EA was delivered at "Zhongwan" (CV 2) and "Zusanli"(ST 36) on the left successively (with disperse-dense wave, 2 Hz/15 Hz in frequency and 2 mA in intensity); and it was performed at one acupoint for 1 min. Using multiple physiological signal collecting system, the intragastric pressure was measured 1 min before EA and in 0 s to 60 s, 0 s to 30 s and 30 s to 60 s of EA in the rats of each group, separately. The change rate of intragastric pressure was calculated to compare the effect size among groups.

RESULTS: 1) Compared with that before intervention, in the normal group, the intragastric pressure was dropped in 0 s to 60 s, 0 s to 30 s and 30 s to 60 s of EA at "Zhongwan" (CV 12) ( P< 0.01); and it was elevated in 0 s to 60 s and 30 s to 60 s of EA at "Zusanli" (ST 36) ( P< 0.01). 2) In 0 s to 60 s, 0 s to 30 s and 30 s to 60 s of EA at "Zhongwan" (CV 12), the intragastric pressure decreased when compared with that before intervention in both the vagectomy group and the splanchnicotomy group ( P< 0.01, P< 0.05); and it increased in 0 s to 60 s, 0 s to 30 s and 30 s to 60 s of EA at "Zusanli" (ST 36) in the splanchnicotomy group ( P< 0.05). 3) Compared with the normal group, the inhibition effect size was reduced in 30 s to 60 s of EA at "Zhongwan" (CV 12) in the vagectomy group ( P <0.01), and in 0 s to 30 s and 30 s to 60 s of EA at "Zhongwan" (CV 12) in the splanchnicotomy group ( P< 0.01). During EA at "Zhongwan" (CV 12) for 0 s to 30 s and 30 s to 60 s, the inhibition effect size was declined more obviously in the splanchnicotomy group when compared with that in the vagectomy group ( P <0.01). The excitation effect size was dropped in the vagectomy group when EA at "Zusanli" (ST 36) for 30 s to 60 s compared with the normal group ( P <0.01), while it increased during 0 s to 30 s in the splanchnicotomy group ( P <0.05). Compared with that of the vagectomy group, the excitation effect size increased more remarkably in the splanchnicotomy group when EA at "Zusanli" (ST 36) for 0 s to 30 s and 30 s to 60 s ( P <0.01).

CONCLUSIONS: Electroacupuncture at the acupoints of different regions differ in the response time and neuromechanism for regulating gastric motility of normal rats. The response time at "Zhongwan" (CV 12) is short and the effect of this acupoint works fast within 30 s; while that at "Zusanli" (ST 36) is prolonged and the effect starts 30 s later. In 0 s to 30 s of EA, the effect of "Zhongwan" (CV 12) and "Zusanli" (ST 36) is predominated by the splanchnic nerve; and in 30 s to 60 s, the effect of "Zhongwan" (CV 12) may be co-innervated by the splanchnic nerve and the vagus nerve, and that of "Zusanli" (ST 36) only by the vagus nerve.