Thirst

The homeostasis of body fluid traditionally is viewed as involving the regu lation of its osmolality and of blood volume. However, the control of thirs t is more complex than can be described in a two-factor model, and consider ation of plasma sodium concentration and of arterial blood pressure also mu st be included in the discussion. This review is organized around those fou r variables and focuses on the seven distinct signals that appear to influe nce water intake in rats. These signals-include four that are excitatory fo r thirstincreased plasma osmolality detected by cerebral osmoreceptors, dec reased blood volume presumably detected by cardiac stretch receptors, incre ased circulating levels of angiotensin II detected by angiotensin II recept ors in the subfornical organ, and increased gastric sodium load apparently detected by putative sodium receptors in the abdominal viscera. There also appear to be three signals that inhibit thirst decreased plasma osmolality detected by, cerebral osmoreceptors, increased arterial blood pressure dete cted by arterial baroreceptors, and increased gastric water load apparently detected by putative sodium receptors in the abdominal viscera. Nutrition 2000;16:821-826. (C) Elsevier Science Inc. 2000.