The role of mouth state in the termination of drinking behavior in humans

Drinking behavior produces a reduction in the unpleasant dry-mouth sensatio ns that accompany thirst. However, it is unclear whether or not the termina tion of drinking behavior is governed by a mechanism that meters this proce ss. Twenty-two participants were tested in both a "dry mouth" and a control condition. In the dry-mouth condition, they exercised for 20 min. Particip ants then placed two cotton-wool rolls in each cheek, adjacent to the upper and the lower teeth with the mouth closed, and then drank water through a straw until they felt satiated. The control condition was identical except that participants placed only a single roll in each cheek, adjacent to the lower teeth. Pilot testing confirmed that using two rolls in each cheek red uced saliva volume in the main oral cavity more effectively than one roll. In both conditions, thirst increased after exercise. However, intake volume s, the number of drinking bouts, and the duration of the drinking episodes, were significantly greater in the dry-mouth condition (means; episode = 93 .8 s, bouts = 7.0, volume = 428 mt) than in the control condition (means; e pisode = 69.3 s, bouts = 4.7, volume = 300 mt). These findings suggest that the termination of drinking behavior is governed by changes in mouth dryne ss, More specifically, saliva production increases during drinking, and thi s attenuates the need to continue drinking to relieve mouth dryness. (C) 20 00 Elsevier Science Inc. All rights reserved.