Effect of stimulating peripheral and central neural pathways on pharyngeal muscle contraction timing during swallowing in dogs.

The effect of stimulating peripheral and central neural pathways on the electromyographic activity in the hyopharyngeal, thyropharyngeal, and cricopharyngeal muscles was studied in eight dogs during 1) eating, 2) unilateral electrical stimulation of the superior laryngeal nerve, and 3) unilateral electrical stimulation of the solitary nucleus. The duration of pharyngeal swallowing was significantly shorter during eating than during stimulation of the solitary nucleus in the anesthetized dog (mean difference 127 ms, SEM 9, n = 15). The duration of pharyngeal swallowing was significantly shorter during eating than during stimulation of the superior laryngeal nerve in the awake dog (mean difference 84 ms, SEM 13, n = 9). The duration of pharyngeal swallowing during stimulation of the superior laryngeal nerve under anesthesia was significantly shorter than during stimulation of the solitary nucleus under anesthesia (mean difference 58 ms, SEM 18, n = 9). The difference in duration of pharyngeal swallowing during stimulation of the superior laryngeal nerve between the awake state and during anesthesia was not significant (mean 19 ms, SEM 14, n = 9). It was concluded that stimulation of peripheral and central neural pathways resulted in different pharyngeal muscle contraction timing during swallowing in dogs.