Sleep rebound in animals deprived of paradoxical sleep by the modified multiple platform method

The objective of the present study was to assess the sleep rebound of animals exposed to the modified multiple platform method (MMPM), in which cage-mate rats were placed onto narrow platforms (NP=6.5 cm in diameter), onto wide platforms (WP=14 cm in diameter) or onto a grid (GR). The last two groups were included as environmental controls for the deprivation method. Animals were implanted with bipolar electrodes in the cortex, hippocampus and neck muscle. Baseline sleep was recorded for 6 h, after which the animals were placed in one of the above-mentioned settings for 90 h and their sleep was again recorded. Comparison between baseline and post-GR recordings revealed no sleep differences in these animals. Placement of animals onto WP resulted in augmented sleep time (16%), time spent in PS (+99%), duration of PS episodes (+77%), sleep efficiency (+16%), and in reduced latency to PS (-84.8%). Finally, NP animals exhibited a dramatic increase in Sleep time (+34.3%), time spent in PS (+184.7%), duration of PS episodes (+106%), and in sleep efficiency (+34.4%). Moreover, sleep latency (-52.2%) and time spent in SWS (-12.2%) were reduced. Based on the results of sleep rebound, the data indicated that placement of animals onto narrow platforms in the MMPM was an effective PS deprivation method and the grid should be considered as an adequate environmental control. (C) 2000 Elsevier Science B.V. All rights reserved.