Electroacupuncture Ameliorates Gastric Hypersensitivity via Adrenergic Pathway in a Rat Model of Functional Dyspepsia

Objective: Electroacupuncture (EA) is effective in treating visceral pain associated with functional dyspepsia (FD). The aim of this study was to explore the effect of chronic EA (CEA) on gastric hypersensitivity and the involvement of sympathetic nervous system in a rodent model of FD. Materials and Methods: Gastric hypersensitivity in adulthood was induced by iodoacetamide (IA) in neonatal rats. The IA-treated rats were randomized to receive no treatment (control), sham-CEA, CEA, or adrenergic antagonists, for one week. Gastric sensitivity to graded gastric distensions was then assessed by electromyogram (EMG) analysis. Autonomic functions were assessed from the spectral analysis of heart rate variability (HRV) to derive the low-frequency (LF, sympathetic activity) and high-frequency (HF, mainly vagal activity) components expressed as percentage of total spectral power. Blood was collected for the measurement of corticosterone (CORT) and norepinephrine (NE). Results: 1) CEA, but not sham-CEA, reduced the EMG response to graded gastric distension in IA-treated control rats at 40 mmHg (128 ± 6% vs. 171 ± 15%, p = 0.009), 60 mmHg (204 ± 14% vs. 271 ± 24%, p = 0.010) and 80 mmHg (269 ± 19% vs. 364 ± 33%, p = 0.025), respectively. 2) CEA, but not sham CEA, increased HF component (0.61 ± 0.02 vs. 0.46 ± 0.04 in IA-treated rats, p = 0.003) and decreased LF component (0.39 ± 0.02 vs. 0.54 ± 0.04, p = 0.003). 3) Adrenergic antagonists reduced the EMG response to graded gastric distension. 4) CEA significantly reduced plasma CORT and NE in IA-treated rats. Conclusions: EA ameliorates gastric hypersensitivity in IA-treated rats and the effect may be related to the improved sympathovagal balance and the decrease of stress hormones.