Multi-targeting regulation of auricular vagus nerve stimulation on gastric hypersensitivity and gastric dysmotility in a rodent model of functional dyspepsia

Abstract

Background: Evidences have shown the auricular vagus nerve stimulation (aVNS) is effective for functional dyspepsia (FD) recently. This study aimed to observe the mechanism of aVNS on facilitatory mediators of the inflammation in a rat model of functional dyspepsia. Methods: Thirty-six 5 d-old male Sprague Dawley rats were randomly divided into control groups (n = 12), model group (n = 12), aVNS group (n = 6) and sham-aVNS group (n = 6). Except for the control rats, all other rats were treated with iodoacetamide gavage. After the model was developed successfully, rats in aVNS group and sham-aVNS group received aVNS and sham-aVNS respectively, 30 min/1 time per day for 14 consecutive days. The control group and model group received no intervention. Gastric sensitivity after 1-week of intervention and gastric emptying after 2-week of intervention were adopted to assess the effect of aVNS. Brain-gut peptides, facilitatory mediators of the inflammation in serum were tested by ELISA, and α7 nicotinic acetylcholine receptor (α7-nAchR) in antrum tissue were tested by Immunohistochemistry to explore the mechanism of aVNS. Results: Compared with the control group, the gastric sensitivity was increased, gastric emptying decreased, and there was no structural damage in the gastric antrum in the model group. aVNS reduced visceral hypersensitivity and improved gastric emptying but not sham-aVNS. cholecystokinin, glucagon-like peptide-1, peptide, tumor necrosis factorα and interleukin 6 were all increased, while ghrelin and α7-nAchR decreased in model rats (P < 0.01 for all, compared with the control group). aVNS can normalize them. Conclusion: The aVNS can decrease the gastric sensitivity and increase gastric emptying, the mechanism was related to its regulation of brain-gut peptides and facilitatory mediators of the inflammation. The ameliorating effect was related to cholinergic mechanism.