Effect of body weight reduction on spontaneous wheel running in rats

Abstract

Twenty-nine Wistar rats were tested for their spontaneous wheel running activity in daily 1-h sessions first under a free-feeding condition for 7 days, next with body weights decreased to 85% of their free-feeding weights. In the free-feeding phase, the number of wheel turns did not increase over the phase. In the 85%-body-weight phase, the number of wheel turns increased over the phase. In contrast, the number of wheel turns per 3 minutes decreased from the start to the end of the session on day 1 and day 7 of both phases. And, the number of wheel turns in the 85%-body-weight phase was greater on day 7 than on day 1. Spontaneous wheel running can reinforce other operant responses and such self-reinforcing mechanisms could be more effective during the 85%-body-weight phase.