Electroacupuncture at “Lianquan” (CV23) improves post-stroke dysphagia via hypoglossal nucleus

To investigate the mechanisms by which the hypoglossal nucleus (12N) modulates swallowing-related activities and mediates the therapeutic effects of electroacupuncture (EA) at “Lianquan” (CV23) in alleviating post-stroke dysphagia (PSD).

Tracer viruses were used to investigate the brain regions that directly project to CV23. C57BL/6J mice were divided into 7 groups: control, model, model+EA, normal+12N inhibition control, normal+12N inhibition, model+EA+12N inhibition control, and model+EA+12N inhibition groups (7 mice/group). Three additional C57BL/6J mice were used for the virus tracing experiment. A photochemical thrombosis model was established in C57BL/6J mice to simulate PSD, by intraperitoneally injecting 0.2 mL of 1.5% rose bengal solution combined with laser irradiation to induce ischemic pathological changes in the primary motor cortex; EA at CV23 (2 Hz, 1 mA, for 15 minutes, once in total) to study the effect of electroacupuncture on swallowing function in PSD mice. Chemogenetic viral inhibition was applied to suppress neuronal activity in the 12N, and changes in vocal fold movements and swallowing electromyography were observed under physiological conditions, by laryngoscopy and electrophysiological recorder respectively. After PSD model establishment, EA combined with chemogenetic inhibition of 12N was followed to observe the effect of chemogenetic inhibition of 12N on EA at CV23 in improving PSD. Tracer viruses were used to trace the upper brain region of the 12N.

The 12N directly projected to the surrounding tissues of CV23. Compared with the control group, in the model group, food residues were observed in the pharyngeal cavity and piriform recesses, along with prolonged vocal cord movement cycle time, a reduced number of vocal cord movement cycles within 10 seconds (P<0.01), and decreased electromyographic area under the curve as well as reduced number of swallows (P<0.001, P<0.01). Compared with the model group, the model+EA group showed shortened vocal cord movement cycle time, an increased number of vocal cord movement cycles within 10 seconds (P<0.01), and an enlarged electromyographic area under the curve (P<0.001). Physiologically, compared with the normal+12N inhibition control group, the normal+12N inhibition group showed a reduction in the area under the swallowing electromyography curve and a decrease in the number of swallows (P<0.05). Pathologically, laryngoscopy showed that compared with the model+EA+12N inhibition control group, the vocal fold movement cycle time of the model+EA+12N inhibition group was prolonged, and the number of movement cycles within 10 seconds was reduced (P<0.01), the area under the swallowing electromyography curve was decreased (P<0.05). The upstream brain regions of the 12N projecting to the surrounding tissues of CV23 were mainly identified in the nucleus tractus solitarii (NTS), intermediate reticular nucleus (IRt), spinal trigeminal nucleus caudalis (SP5C) and lateral paragigantocellular nucleus (LPGi), etc.

The 12N directly projects to the surrounding tissues of CV23 and contributes to EA-mediated improvement in PSD.