Brain Mechanisms of Thirst

“体内平衡”的概念（身体倾向于平衡各种因素以维持稳定的内部状态的想法）是目前大多数对摄入行为的解释的关键部分，特别是水和盐的摄入。然而，包括罗兰博士自己的观察在内的一些观察表明，这种对摄食行为的机制和组织的看法过于简单。这个研究项目将以几种新的方式对体内平衡模型进行严格的检验，包括使用一种假装喝水的大鼠制剂，在这种制剂中，摄入的液体通过一根管子从动物的胃中流出。罗兰博士和其他人的研究表明，与正常饮酒相比，缺水会增加假饮酒。然而，令人惊讶的是，罗兰博士无法在假定的基本口渴刺激、低血容量（低血容量）和高渗透压（血液中溶解的化学物质浓度高）的情况下产生更大的假饮酒增加。第一个实验将在一天的不同时间使用不同的盐施用路线，以评估这一惊人发现的普遍性。罗兰博士还将研究饮水的微观结构（爆发和停顿），并试图评估极短期反馈回路对口腔饱腹感的作用，这种反馈回路可能会超越生理口渴信号（因此独立于液体稳态的控制）。虽然这种口服饱腹感因素多年来一直受到怀疑，但它们从未得到令人信服的分析。第二和第三个实验将处理控制盐摄入量的口服和全身因素，再次使用假摄入作为实验工具，将口服和全身（摄入前和摄入后）因素分开。由于盐偏好的遗传差异，至少有两种不同的大鼠将被研究。罗兰博士希望能够通过对假饮酒的微观结构分析来评估这种基因差异影响行为的机制。Rowland博士的研究为口腔因素作为维持体液平衡的主要机制提供了新的理论重要性，并对控制行为的系统状态和环境刺激之间的相互作用具有更广泛的意义。

The concept of "homeostasis" (the idea that the body tends to balance various factors to maintain a stable internal state) is a key part of most current explanations of ingestive behavior, in particular water and salt intake. However, a number of observations, including Dr. Rowland's own, suggest that this is too simple a view of the mechanism and organization of ingestive behaviors. This research project will critically examine the homeostatic model in several new ways, including the use of a sham-drinking rat preparation in which ingested fluids are lost through a tube from the stomach out of the animal. Dr. Rowland and others have shown that water deprivation increases sham drinking more than normal drinking. Surprisingly, however, Dr. Rowland has been unable to produce this greater increase in sham drinking with the presumed elementary thirst stimuli, hypovolemia (low blood volume) and hyperosmolarity (high concentration of chemicals dissolved in the blood). The first experiment will use different routes of administration of salt at different times of day in order to assess the generality of the surprising finding. Dr. Rowland will also examine the microstructure (bursts and pauses) of drinking and attempt to assess the role of very-short-term feedback loops on oral satiety that may override physiologic thirst signals (and thus be independent of the controls of fluid homeostasis). While such oral satiety factors have been suspected for many years, they have never been analyzed convincingly. The second and third experiments will deal with oral versus systemic factors in the control of salt intake, again using sham ingestion as an experimental tool to separate oral from systemic (pre- and post-ingestional) factors. At least two different strains of rats will be studied because of genetic differences in salt preference. Dr. Rowland hopes to be able to assess, from microstructural analysis of sham drinking, the mechanisms by which this genetic difference affects behavior. Dr. Rowland's studies place a new theoretical importance on oral factors as primary mechanisms in maintaining fluid balance and have wider implications for the interplay between systemic states and environmental stimuli in the control of behavior.