Swimming immobility of REM sleep deprived rats reared in different environments

This study tested the hypothesis that environmental rearing treatments which alter the REM sleep levels of rats affect swimming immobility, an adaptive, REM sleep sensitive behavior. At weaning, 72 female Sprague-Dawley rats were maintained in either an enriched, an impoverished, or a social control environment for 32-33 days. They were then placed in either a REM sleep depriving platform-in-water condition or in one of two control conditions (large platform or dry control) for 4 days before being scored for swimming immobility during a 10-min swimming test. A 3 (environments) X 3 (platforms) ANOVA revealed a main effect for environments, F(2,63) = 5.20, p less than 0.01. Enriched rats exhibited a behavioral advantage over impoverished rats under the large platform control condition, F(1,63) = 6.58, p less than 0.025, and under the dry control condition, F(1,63) = 6.14, p less than 0.025. However, under the REM depriving condition, their behavioral advantage was virtually eliminated, F(1,63), p less than 1. The conclusion that the REM sleep levels of the rat groups probably determined their swimming immobility scores is discussed.