Oro-gastro-intestinal inhibition of hypernatremia-induced drinking in the goat

Reduction of drinking by slow (5 ml/min) administration for 20 min of nearly body-warm (35 degrees C) and cold (15 degrees C) water into the mouth, the abomasum, or the duodenal bulb was studied in goats made thirsty by the simultaneous i.v. infusion of hypertonic (2 M) NaCl at 2 ml/min. During the control experiments the drinking response to corresponding infusion of 1.7 M NaCl was recorded. This in order to eliminate the possible influence on the results of a postabsorptive thirst inhibition which would occur if the administered water was completely absorbed already during the saline infusion. The entrance of warm water into the mouth or into the abomasum caused about 20%, and into the duodenal bulb about 30% reduction of drinking during the infusion of hypertonic NaCl. The corresponding reduction for cold water was when introduced into the mouth and duodenal bulb about 50% and into the abomasum about 60%. Cold water also considerably delayed the onset of drinking. The inhibition obtained during cold water administration was partially compensated for by increased post-infusional drinking. As regards the sensory input underlying preabsorptive inhibition of thirst, it is concluded that (regardless of distension, swallowing, and other mechanical factors) the entrance of pure water into various parts of the alimentary tract contributes to reduce the thirst drive. In addition, stimulation of oral, gastric, and duodenal cold receptors obviously diminish the urge to drink considerably.