Orogastric, hydrational, and behavioral controls of drinking following water deprivation in rats

Drinking and its associated behaviors were studied in rats deprived of fluid for 8,24, or 48 hr. The behavior of rats drinking water could be divided into three successive stages: (a) an initial intense burst of drinking that could not be easily disrupted; (b) intermittent drinking, often distinguished by the brief appearance of conflict behavior directed at the drinking spout; and (c) termination of drinking. Drinking stopped well before the fluid loss, reflected in a sizable extracellular deficit, was restored. Intake of water was terminated when serum hyponatremia and hypoosmolality (and presumably cellular overhydration) developed in temporal continguity with drinking. These and other considerations suggest that the cellular fluid phase exerts significant inhibitory as well as excitatory control over drinking.