Cholinergic neurons in the dorsal nucleus of the vagus nerve are involved in the mechanism of action of electroacupuncture at HT7 in a mouse model of chronic heart failure

Objective: To investigate the role and mechanism of the dorsal motor nucleus of the vagus nerve (DMV) in the effects of electroacupuncture (EA) at HT7 in a mouse model of chronic heart failure (CHF). Methods: A CHF model was established in male C57 mice by ligating the anterior descended branch of the left coronary artery. In part I of the experiment, mice were randomly divided into Control, untreated model (CHF) and EA-treated model (CHF + EA) groups (n = 6 each). In part II, mice were randomly divided into the following groups (n = 6 each): EA-treated model group (CHF + EA); EA-treated model group receiving cholinergic neuron promoter chemogenetic activating virus encoding human M4 muscarinic (hM4) receptor (hM4D) and clozapine-N-oxide (CNO) (CHF + hM4D + CNO + EA); EA-treated model group additionally receiving “empty” virus encoding enhanced green fluorescence protein (EGFP) and CNO (CHF + EFGP + CNO + EA); EA-treated model group receiving hM4D only (CHF + hM4D + EA); and EA-treated model group receiving CNO only (CHF + CNO + EA). All mice except those in the Control and CHF groups were treated with bilateral EA at HT7 (frequency 2 Hz, intensity 2mA, pulse width 0.2 ms ± 20%) once a day (20 min each time) for 7 days. Left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), scar area and serum inflammatory factor levels were evaluated using a Doppler ultrasound imaging system, Masson staining, ELISA and other methods. Results: Compared with the Control group, LVEF/LVFS in the CHF group decreased ( p < 0.001), the scar area was larger, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and interleukin (IL)-6 levels increased significantly, and acetylcholine (ACh) decreased significantly ( p < 0.001) in the CHF group. Compared with the CHF group, LVEF/LVFS increased ( p < 0.001), scar area was smaller, ANP, BNP and IL-6 decreased significantly and ACh increased significantly ( p < 0.001) in the CHF + EA group. Compared with the CHF + EA group, the CHF + hM4D + CNO + EA group exhibited a decrease in LVEF/LVFS ( p < 0.001), a larger scar area, a significant increase in ANP, BNP and IL-6, and a significant decrease in ACh ( p < 0.001),while there was no significant difference in each index between the CHF + CNO + EA and CHF + hM4D + EA groups ( p > 0.05). Compared with the CHF + hM4D + CNO + EA group, the CHF + EGFP + CNO + EA exhibited an increase in LVEF/LVFS ( p < 0.001), a smaller scar area, a significant decrease in ANP, BNP and IL-6, and a significant increase in ACh ( p < 0.001). Conclusion: Electroacupuncture at (HT7) may activate DMV Ach and reduce myocardial fibrosis, thereby improving CHF, in a mouse model.