Abstract: BACKGROUND: Previous clinical studies have found that acupoint dressing therapy using Expectorant Choking Formula is effective in improving swallowing function in patients with post-stroke swallowing disorders, but the mechanism of action is unclear. In the brainstem swallowing center, the nucleus ambiguus is the main component of the swallowing center in the ventral region, which can induce swallowing movements and swallowing time, while glutamate receptors, γ-aminobutyric acid receptors, and c-fos protein in the nucleus ambiguus are closely related to swallowing.
OBJECTIVE: To investigate the effects of acupoint dressing therapy using Expectorant Choking Formula on the expression of glutamate receptors, γ-aminobutyric acid receptors, and c-fos protein in the nucleus ambiguus of rats with ischemia-reperfusion injury, and to investigate the mechanism of swallowing disorder in rats with cerebral ischemia-reperfusion treated by acupoint dressing therapy using Expectorant Choking Formula. 
METHODS: Seventy Sprague-Dawley rats were randomly divided into normal group (n=16), ischemia-reperfusion injury model group (n=18), patching group (n=18), and sham patching group (n=18). The model group, patching group, and sham patching group were modeled by reperfusion after 90 minutes of transient cerebral ischemia using the thread-occlusion method. After 6 hours of modeling, neurological function was scored and the rats with a score of 2 were selected for subsequent experiments. The rats were treated with acupoint dressing therapy using Expectorant Choking Formula on the second day of modeling, the sham patching group was given drug-free dressing on the basis of the model preparation, and the other two groups were kept normally for 1 month. Body mass, swallowing initiation response time and the number of swallows were recorded in each group on days 2, 7, 14 and 30 after modeling. After 4 weeks of treatment, the water content in brain tissue was measured; the expression of gamma-aminobutyric acid A receptor α1, N-methyl-D-aspartate receptor 1 and c-fos protein in the nucleus ambiguus of the medullary swallowing center was detected by immunohistochemistry, RT-PCR and western blot.
RESULTS AND CONCLUSION: Compared with the normal group, the body mass, the number of swallows within 1 minute and swallow initiation reaction time of rats in the model, patching and sham patching groups decreased on days 14 and 30 after modeling (P < 0.05), and the swallow initiation reaction time was prolonged (P < 0.05); on day 30, the body mass and the number of swallows of rats increased in the patching group compared with the model group (P < 0.05), while the swallowing initiation time was shortened (P < 0.05). After 4 weeks of treatment, the water content of brain tissue was significantly reduced in the patching group compared with the model group (P < 0.05). Compared with the model group, the positive expression and the mRNA and protein expression of gamma-aminobutyric acid A receptor α1 in the nucleus ambiguus of the medulla oblongata were increased in the patching group but still lower than those in the normal group; the positive expression and the mRNA and protein expression of N-methyl-D-aspartate receptor 1 and c-fos were decreased in the patching group but significantly higher than those in the normal group (P < 0.05). These findings indicate that the acupoint dressing therapy using Expectorant Choking Formula could improve the swallowing function of rats with post-stroke swallowing disorder, and its mechanism of action might be related to improving the degree of brain edema, regulating the neurotransmitters glutamate receptors, gamma-aminobutyric acid A receptors and c-fos protein levels in the nucleus ambiguus.

Key words: swallowing disorder, transient cerebral ischemia-reperfusion, nucleus ambiguus, brain edema, gamma-aminobutyric acid A receptor α1, N-methyl-D-aspartate receptor 1, c-fos