Acupuncture at Gastric Back-Shu and Front-Mu Acupoints Enhances Gastric Motility via the Inhibition of the Glutamatergic System in the Hippocampus

A central amygdala input to the dorsal vagal complex controls gastric motility in mice under restraint stress

Background/aims: Psychological and physiological stress can cause gastrointestinal motility disorders. Acupuncture has a benign regulatory effect on gastrointestinal motility. However, the mechanisms underlying these processes remain unclear. Methods: Herein, we established a gastric motility disorder (GMD) model in the context of restraint stress (RS) and irregular feeding. The activity of emotional center-central amygdala (CeA) GABAergic neurons and gastrointestinal center-dorsal vagal complex (DVC) neurons were recorded by electrophysiology. Virus tracing and patch clamp analysis of the anatomical and functional connection between the CeA^GABA → dorsal vagal complex pathways were performed. Optogenetics inhibiting or activating CeA^GABA neurons or the CeA^GABA → dorsal vagal complex pathway were used to detect changes in gastric function. Results: We found that restraint stress induced delayed gastric emptying and decreased gastric motility and food intake. Simultaneously, restraint stress activated CeA GABAergic neurons, inhibiting dorsal vagal complex neurons, with electroacupuncture (EA) reversing this phenomenon. In addition, we identified an inhibitory pathway in which CeA GABAergic neurons project into the dorsal vagal complex. Furthermore, the use of optogenetic approaches inhibited CeA^GABA neurons and the CeA^GABA → dorsal vagal complex pathway in gastric motility disorder mice, which enhanced gastric movement and gastric emptying, whereas activation of the CeA^GABA and CeA^GABA → dorsal vagal complex pathway mimicked the symptoms of weakened gastric movement and delayed gastric emptying in naïve mice. Conclusion: Our findings indicate that the CeA^GABA → dorsal vagal complex pathway may be involved in regulating gastric dysmotility under restraint stress conditions, and partially reveals the mechanism of electroacupuncture.

The Influence of Stomach Back-Shu and Front-Mu Points on Insular Functional Connectivity in Functional Dyspepsia Rat Models

Functional Dyspepsia (FD) is a common functional gastrointestinal disease, which can reduce the quality of life in patients. Prior research has indicated that insula is closely related to FD and that acupuncture can regulate the functional connectivity (FC) of FD. Therefore, we hypothesized that acupuncture on FD was effected through the insular pathway. To test our hypothesis, we performed electroacupuncture (EA) on FD rat models and then examined the FC between insula and other brain regions through resting-state functional magnetic resonance imaging (rs-fMRI). Seven-day-old male infant Sprague-Dawley (SD) rats were randomly divided into control group, FD model group, and FD acupuncture group, with twelve rats per group (n = 36). Upon establishing successful models, the FD acupuncture group was subjected to EA intervention using Stomach back-shu (BL-21) and front-mu (RN-12) points for ten consecutive days for durations of 20 minutes each day. After intervention, each group was subject to rs-fMRI. The digital image data obtained were analyzed using FC analysis methods. Subsequently, gastric ligation was performed to measure gastric emptying rates. Before EA intervention, the FD model group exhibited decreased functional connections between the insula and a number of brain regions. After EA intervention, FD acupuncture group exhibited increasing FC between insula and regions when compared to the FD model group, such as the primary somatosensory cortex (S1), hippocampal CA3 (CA3), polymorphic layer of dentate gyrus (PoDG), caudate putamen (CPu), and oral pontine reticular nuclei (PnO) (P < 0.05); decreasing FC was also exhibited between insula and regions such as the bilateral primary and secondary motor cortexes (M1/2), paraventricular hypothalamic nucleus (PVA), and limbic cortex (LC). These findings indicate that the effective treatment of FD using EA may be through regulating the abnormal FC between insula and several brain regions, in particular CA3, PoDG, and PVA.