Effect Of Auricular Acupuncture (Vagus Nerve Stimulation) On Gastrointestinal Motility And Its Relationship With Vagal Activity

Background: Vagus nerve stimulation is capable of regulating autonomic nervefunction. In Traditional Chinese Medicine, the effect of auricular acupuncture ismediated by the vagus. There is a closely relationship between gastrointestinal (GI)motility and vagus, and acetylcholine (Ach) releasing from the ending branch ofvagal nerve could promote GI motility. Developed based on these facts, this study isdesigned to investigate auricular acupuncture’s effect on GI motility as well as therelationship of this effect with the vagus nerve.Methods:50rats were divided into5groups for observation of effects of differenttypes of acupuncture and influencing factors: control, auricular acupuncture (AA),somatic acupuncture (SA), atropine, and atropine+AA. The acupuncture points usedfor AA were the “Stomach” and “Small intestine”, whereas the SA point was ST-36.In addition, electroacupuncture (EA) was performed for15minutes for each group.A model of reduced GI motility was established using ethanol, and GI transit ratewas used to measure GI motility. Heart rate variability and the effect of atropineadministration were included in data collection to study the relationship between AAand vagal activity.Results: The GI transit rate was observed to increase in both AA and SA groupscompared with control, and no significant difference was found between their effects.In addition, after atropine was administered to the mice, AA was found to beineffective in influencing GI transit rate. In the HRV analysis, no significant differences were found in the absolute low-frequency normalised units,high-frequency normalised units or the low frequency/high frequency componentratio in AA or SA compared with control. After the rats were given atropine, AA stillhad no effect on HRV.Conclusions: AA’s function in improving GI motility was similar to that of SA, andthis effect could be blocked by presence of atropine, indicating that this effect wasregulated by the vagus. However, HRV did not reflect the acupuncture-inducedchanges in vagal nerve function.