Abstract
In the present study, the role of sensory inputs from oral mucosal receptors in voluntary swallowing in humans was investigated. Twenty healthy volunteers were enrolled. A fine tube was inserted into the pharyngolaryngeal region (PL). In animal experiments, it has been reported that excitation of laryngeal water receptors elicit swallowing reflex and 0.3 M NaCl strongly inhibits water receptors. In this study, water or 0.3 M NaCl solution was delivered into the PL through this tube at slow infusion rates (0.2-5.0 ml/min). Each subject was instructed to repeat swallowing as fast as possible. The swallowing interval (SI) between two consecutive swallows in each infusion was measured. SIs were shorter in the case of water infusion than in the case of 0.3 M NaCl. Increasing infusion rate shortened SIs. The results suggest that sensory inputs from water and mechanical receptors can facilitate voluntary swallowing. Values of SI with surface anesthesia of the PL (diminution of sensation) by voluntary swallowing varied greatly in the subjects, suggesting that the ability of the swallowing center to perform repetitive voluntary swallowing varies among subjects. There was a linear relationship between SI with anesthesia and the sensory effect: the longer the SI with anesthesia was, the stronger was the sensory effect. It appears that sensory inputs in the PL strongly compensate for difficulty in swallowing in subjects showing a long SI. [J Physiol Sci. 2007;57 Suppl:S100]
