Interaction between primary afferent nerves in the elicitation of reflex swallowing.

In adult cats anesthetized with urethan, a number of observations were made that support the concept that some control over the rate of reflexly induced swallowing occurs in the intermediate network at the level of the nucleus of the solitary tract. It was shown that different nerves, e.g., the two superior laryngeal and glossopharyngeal nerves, when activated in sequence interact in such a manner as to facilitate reflex swallowing. It was also shown that the decrement in the reflex response observed to continuous stimulation of a primary afferent nerve, e.g., one superior laryngeal, can be reversed by switching the stimulation to another nerve either on the same or contralateral side. And finally, following discrete medullary lesions, it was observed that that portion of the nucleus of the solitary tract located 2 mm or more rostral to the rostralmost point of the dorsal medial sulcus appears to contain an integral component of the intermediate network that governs reflexly induced swallowing, whereas lesions restricted to the ventrolateral portion of the nucleus of the solitary tract have no effect on the reflex response.