Electroacupuncture at ST36 ameliorates gastric dysmotility in rats with diabetic gastroparesis via the nucleus tractus solitarius-vagal axis

BACKGROUND Diabetic gastroparesis (DGP), characterized by delayed gastric emptying and impaired motility, poses significant therapeutic challenges due to its complex neural and molecular pathophysiology. Emerging evidence suggests that electroacupuncture (EA) at ST36 modulates gastrointestinal function; however, the precise neuromolecular pathways underlying its efficacy in DGP remain incompletely defined. AIM To elucidate the neural mechanisms underlying EA at ST36 improving DGP gastric motility through the nucleus tractus solitarius (NTS)-vagal axis. METHODS The DGP model was established via a single high-dose intraperitoneal injection of 2% streptozotocin combined with an 8-week high-sugar/high-fat diet. Interventions included EA at ST36, pharmacological modulation [choline acetyltransferase (ChAT) agonist polygalacic acid (PA) and inhibitor antagonist alpha-NETA], and subdiaphragmatic vagotomy. Post-intervention observations included body weight and blood glucose levels. Gastric emptying was evaluated using phenol red assays, gastric slow-wave recordings, and dynamic positron emission tomography-computed tomography imaging. Histopathological analysis (hematoxylin-eosin staining) and molecular assessments (Western blot, immunofluorescence) were performed to quantify gastric smooth muscle-associated factors [neuronal nitric oxide synthase (nNOS), cluster of differentiation 117 (C-kit), stem cell factor (SCF)] and vagal targets [ChAT, α7 nicotinic acetylcholine receptor (α7nAChR)] in the ST36 acupoint region, L4-L6 spinal segments, and NTS. Gastrointestinal peptides [gastrin (Gas), motilin (MLT) and vasoactive intestinal peptide (VIP)] were measured via enzyme-linked immunosorbent assay. RESULTS The study found that EA significantly increased the rate of gastric emptying, restored the slow-wave rhythms of the stomach, and improved the architecture of the smooth muscles in the stomach. This was evidenced by a reduction in inflammatory infiltration and an increase in the expression of nNOS, C-kit, and SCF. Mechanistically, EA activated vagal targets (ChAT and α7nAChR) at ST36, transmitting signals via spinal segments L4-L6 to the NTS, subsequently regulating gastrointestinal peptides (Gas, MLT, VIP) and restoring interstitial cells of Cajal (ICCs) function via subdiaphragmatic vagal efferent pathways. It is crucial to note that subdiaphragmatic vagotomy led to the abrogation of EA-induced enhancements in gastric motility and ICC recovery, thereby confirming the indispensable role of vagal efferent signalling. CONCLUSION EA provides a novel molecular mechanism for improving gastrointestinal motility in DGP via a peripheral stimulation (ST36), spinal afferent (L4-L6), brainstem integration (NTS), vagal efferent (gastric) circuit.