ヒト咽頭・喉頭部への水および食塩水注入による嚥下誘発

抄録

In humans, infusion of water to the pharyngolaryngeal region elicits swallowing. Thus, it has been thought that water receptors reside in the pharyngolaryngeal region. In the present study, we investigated how water receptors are involved in the initiation of swallowing in humans. Ten healthy subjects were studied. Each subject was instructed to repeat swallowing as fast as possible. Water (distilled water) or 0.05-0.3 M NaCl solution was delivered to the pharyngolaryngeal region through a fine tube at slow rates of 0.2, 2.0 and 5.0ml/min. The intervals between two consecutive swallowings in a test were measured. Swallowing intervals increased with increasing concentration of NaCl, suggesting that excitation of water receptors was inhibited by the presence of NaCl. The effect of water on swallowing was determined by subtracting the mean swallowing interval using water from that using 0.3 M NaCl in each subject. Under the same stimulating condition, swallowing intervals varied with subjects. There was a linear relationship between the effect of water on swallowing for eliciting a swallow and the swallowing interval in 10 subjects such that the longer swallowing intervals, the stronger the effect of water on swallowing. Current findings were discussed with respect to the interplay between volition and sensory stimulation in the timing of initiation of swallowings. The present results indicate that the inhibition of water receptors by NaCl is due to Clions. Since saliva secreted in a resting state contains relatively low concentrations of Clions, accumulated secretions of saliva from the pharynx may excite water receptors continuously, thereby shortening the interval between spontaneous swallowings that operate to clear the mouth of saliva.