Introduction: Currently, the conceptualization of thirst is based nearly entirely on osmoregulation, with some acknowledgment of anticipatory-thirst, though with no testable mechanism. Such a model of thirst is unable to explain many thirst-related phenomena, such as why drinking can occur with hypoosmolality or how quantity of intake at a drinking occasion is regulated. Discussion: This model aimed to unify various lines of thinking from different disciplines surrounding thirst by presenting a 4-compartment model comprising true-thirst (primarily osmo-regulated), contextual-thirst (e.g., mouth-breathing), pharmacological-thirst (induced from drugs), and impulsive-thirst (everyday spontaneous drinking). Within this framework, xerostomia (dry mouth) is the primary regulator of drinking, with a further differentiation between a literal dry mouth (“true-xerostomia,” hyposalivation) and the sensation of dry mouth (“sensational-xerostomia,” a typically nonoverwhelming desire to drink based on a feeling of dry mouth without hyposalivation). Based on pharmacological-thirst mechanisms, the cholinergic system is proposed to initiate impulsive-thirst by triggering a (sensation of) dry mouth in everyday life. Food-appetite constructs that are centrally regulated (sensory-specific satiety, palatability, and pleasantness) are applied to thirst to explain everyday drinking patterns. Conclusion: This model helps to explain some anomalies that are thus far unexplained by true-thirst, though there are several other factors which may need to be included after further exploration in the future.

Keywords:
Appetite, Acetylcholine, Hydration, Osmolality, Thirst, Xerostomia

This is a theory paper; no human or animal participants were used as no study was conducted.

H.A.C. has received research funding from the Economic and Social Research Council, the European Hydration Institute, and the Esther Olssons stiftelse II & Anna Jonssons Minnesfond; has conducted research for Tate & Lyle; has received speakers fees from Danone Research; has a scientific advisory role at Hyduro; and holds an honorary research position at the University of Aberdeen.

No funding was acquired for this work.

No data were collected for this theory paper; as such there are no accompanying data. Full paper available from doi: 10.31232/osf.io/q7gvd.

© 2022 The Author(s). Published by S. Karger AG, Basel
2022
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