Drinking characteristics of normal rats and rats heterozygous or homozygous for diabetes insipidus

Abstract

Rats heterozygous for the mutant gene for diabetes insipidus did not drink more water than normal rats without the mutant, but did drink more of dilute quinine solutions (0.03% or less) and ingested more 3% NaCl. Heterozygous rats were the same as normal controls in regard to intake of 20% sucrose and the shape of the circadian rhythm function of drinking. In heterozygous and normal rats, but not rats, homozygous for the mutant, the addition of food deprivation to water deprivation sharply reduced drinking during a subsequent test period. Compared to heterozygous and normal rats, homozygous rats drank more water, more dilute QHCl solution (0.03% or less), but the same amount of concentrated QHCl (0.06 and 0.12%) and approximately the same amount of 20% sucrose. Homozygous rats, in spite of their renal defect, ingested less 3% NaCl than heterozygous rats, but approximately the same amount as normals. Half the homozygous rats died following the self-imposed NaCl load indicating that there is no protective taste-mediated rejection mechanism for NaCl. The circadian rhythm function of drinking was approximately the same shape for all three groups of rats, but the homozygous rats consumed a larger proportion of their daily intake during the light cycle than do the two other genotypes. Water intakes for all three types of rats are less during fasting than during ad lib feeding suggesting that a large segment of the water intakes of the 3 groups probably is utilized to facilitate the feeding and digestion of food.