Initiation of reflex swallowing from the naso- and oropharynx.

SINCLAIR, WILLIAM J. Initiation of rejlex swallowing from the nasoand oropharynx. Am. J. Physiol. 218(4) : 956-960. 1970.~In 15 electrolytically decerebrated cats, the pharynx was exposed surgically from the ventral aspect and divided in the midline. The pharynx was mechanically stimulated with light pressure using a wooden applicator 4 mm in diameter. Swallowing was noted visually and later verified electromyographically. Areas eliciting swallows which occurred within l-3 set after application of the stimulus were recorded on a map of the pharynx. Observations were made on the effects of surface area stimulated, pressure, and movement patterns. The results showed that the posterior pillars were most reflexogenic, the posterior pharyngeal wall was slightly less, and the lateral pharyngeal wall was least reflexogenic. These areas extended into the nasopharynx. Larger diameter probes and heavier pressures appeared to be no more effective. Movement made mechanical stimulation more effective and showed directional sensitivity. Selective sectioning of the glossopharyngeal nerve (GPN) and the pharyngeal branch of the vagus nerve (PhX) demonstrated that the GPN is the prime afferent of the swallow reflex initiated from the pharynx and that the PhX plays a minor role.