Effects of adult-onset calorie restriction on anxiety-like behavior in rats

Calorie restriction (CR) has consistently been shown to increase lifespan and ameliorate disease outcomes. Its effects on behavior are less clear, although anxiolytic-like effects have been observed. Rats were subjected to 1 of 4 dietary regimens: control, CR25%, CR50% and, an acute episode of CR and tested in 3 tests of anxiety: the open field test, the elevated plus maze, and the modified open field test. In the open field test, the CR25% and CR50% groups made more central zone entries than the control and Acute groups, which was primarily due to differences in the initial 5 min of the test. Moreover, both CR groups engaged in greater exploration of the central zone than the control group in the initial 5 min of the test. The Acute group also exhibited significantly longer latencies to leave the central zone at test onset than the control and CR50% group. In the elevated plus maze, the Acute group also displayed longer latencies to open arm entry as compared to the control and CR50% group and showed a lower ratio of open to total arm entries compared to all other groups. There were no effects of CR on any variable of the modified open field test. Possible neurochemical mechanisms underlying the anxiolytic-like effect of CR are discussed. (C) 2007 Elsevier Inc. All rights reserved.