CMAPs in pharyngeal and hyoid muscles evoked by nucleus solitarius stimulation in dogs

Electrical stimulation of the solitary nucleus with a single pulse of 150 to 500 microA caused visible contractions of the muscles involved in swallowing but did not activate the central pattern generator for swallowing. Electromyographically there were short bursts of activity characterized by an onset of activity within 1 to 7 ms, a duration of 14 to 26 ms, and an amplitude of 10 to 4,800 microV. The CMAPs were recorded in the pharyngeal and hyoid muscles on both the ipsilateral and the contralateral sides of the stimulated solitary nucleus. Across all five pairs of muscles in which the recordings were made the latencies of the CMAPs in the contralateral muscles were significantly greater and the amplitudes significantly lower, but the durations were not significantly different. Bilateral activation of the muscles by unilateral stimulation may not result in symmetrical contraction of the pharyngeal muscles.