Relation of route of administration and types of fluid to satisfaction of thirst in the dog

¹ Departments of Medicine and Physiology, University of Colorado, School of Medicine, Denver, Colorado

In 13 dogs, using intravenous injection of 20% sodium chloride as a stimulus for inducing a standardized drinking pattern, the substitution for water of various drinking solutions such as 5% glucose, 5% sucrose, 1.8% urea, 1.3% sodium sulfate, 0.9% sodium bicarbonate, 0.85% ammonium chloride, 1.15% sodium acetate and 0.9% magnesium chloride did not alter significantly the total intake. However, with 0.9% sodium chloride the intake averaged 2.4 times that observed for water. Temperature differences of solution did not significantly alter the intake. Introduction of 0.9% sodium chloride, 5% glucose, 1.8% urea and water into the stomach 40 minutes prior to intravenous injection of 20% sodium chloride had an inhibitory effect on drinking response. When similar solutions were given intravenously 40 minutes prior to the salt injection, there was no inhibition of drinking, in fact, the total intake was increased. In these two situations the different drinking response could not be explained by differences in hematocrit or serum concentrations of protein or chloride. Thus, direct introduction of fluids into the blood stream cannot substitute during the 1st hour for the gastric factor in satiation of thirst.