Gentle Manual Acupuncture Could Better Regulate Gastric Motility and Vagal Afferent Nerve Discharge of Rats with Gastric Hypomotility

Abstract

The variation of stimulus intensity of manual acupuncture (MA) may produce diverse acupuncture effects. However, the intensity-effect relationship and the underlying mechanism of MA are still elusive. In this study, the effects of MA regulation of gastric motility were investigated after lifting-thrusting MA treatment with four different frequencies (1 Hz, 2 Hz, 3 Hz, and 4 Hz) at ST36. The experiments were conducted on rats with gastric hypomotility caused by atropine. The results showed that the gastric motility amplitude decreased after atropine injection, while the treatment of four types of MA affected the gastric motility amplitude in varying degrees. Specifically, 2 Hz MA exhibited the most effective results, while 4 Hz MA had the least effect; the effects of 1 Hz MA and 3 Hz MA were between the effects induced with 2 Hz and 4 Hz. Furthermore, the response of gastric vagal afferent nerve discharge and gastric motility was examined after MA treatment with frequencies of 2 Hz and 4 Hz, respectively, on ST36 in order to elucidate the mechanism of MA regulation of gastric motility. The results showed that 2 Hz MA was able to increase the amplitude of gastric motility and discharge frequency of gastric vagal afferent nerves, while 4 Hz MA exhibited seldom effects. These findings suggest that gentle MA (2 Hz) has more stimulating effects than strong stimulation with MA (4 Hz) on gastric hypomotility. In addition, gastric motility regulated by MA was associated with vagal afferent nerve activation.

Figure 1

Schematic diagram of the experiments.

Figure 2

Gastric motility responses to atropine and MA with different frequencies (1 Hz, 2 Hz, 3 Hz, and 4 Hz) at ST36. (a, b) Changes in the frequency and amplitude of gastric motility induced by atropine and different MA simulations at ST36, respectively (normal, model, 1 Hz, 2 Hz, 3 Hz, and 4 Hz; n = 5, 6, 5, 6, 6, and 6, respectively; ^#p < 0.05 versus the normal group at the indicated time point; ^∗p < 0.05 versus the atropine group at the indicated time point).

Figure 3

Responses of gastric motility and gastric vagal afferent fiber discharge due to atropine and MA treatment with different frequencies (2 Hz and 4 Hz) at ST36. (a, b) Examples of the alterations of gastric motility and gastric vagal afferent fiber discharge induced by atropine and MA stimulations with different frequencies (2 and 4 Hz) at ST36. In each panel, the top trace is the wave of gastric motility, the middle trace is the action potentials of the gastric vagal afferent fibers, and the bottom trace represents the PSTH (1 s bin width). (c, d) Changes in the gastric motility and vagal afferent fibers after the atropine injection and MA stimulation at ST36 (normal, model, 2 Hz, and 4 Hz, and n = 5, respectively; ^#p < 0.05 versus the normal group at the indicated time point; ^∗p < 0.05 versus the atropine group at the indicated time point; ※p < 0.05 versus the 4 Hz group after modeling).