Effect of procurement wheel running on the rate of drinking in rats

Four rats, 22.5 hr deprived of water, were tested in 3 conditions, in which they were required to run zero, 5 or 300 one-sixth revolutions in a wheel to gain 30 min access to water in a drinking tube. The number of licks performed in the 30 min increased monotonically with the procurement cost, and was 20% greater following the larger cost than when there was no cost. However, examination of the rates of drinking throughout the 30 min revealed that differences occurred between the conditions only at the beginning of the period. In the first 3 min there was a monotonic relationship between the proportion of time spent drinking and the procurement cost, but no effect of the cost on the rate could be detected after the first 6 min. The results are consistent with the hypothesis that the effect is mediated by a transient elevation of the subject's arousal level.