Individual Differences in a Physiological Effect of Water Restriction in Rats

Abstract

WHEN their water intake is restricted, rats will learn to run a maze or press a bar to obtain water. Individual rats learn these tasks with varying speeds, and there are many factors which can contribute to speed of learning and hence to differences between individuals. Among these is the possibility that the same amount of time spent without water does not arouse the same “need” for water in different animals. A “need” for water arises at least in part from the dehydration of body tissues and this is in turn reflected by a fall in body weight which is larger than can be accounted for by the concurrent fall in food intake¹. There is little information on changes in body weight consequent on water restriction schedules in different animals. The experiments reported here were concerned with estimating the effect of a standard schedule of water restriction on the body weight of rats varying in age, sex or strain.