Effects of chronic ethanol exposure on sleep in rats

Sleep disturbance is a common complaint in alcoholics. When polysomnographi c studies are performed in alcoholics, reductions in slow wave sleep are a common finding; however, few studies have evaluated the effects of chronic alcohol exposure on sleep in animal models. In the present study, the sleep EEG was evaluated in 40 Wistar rats who were exposed to chronic alcohol or control conditions in vapor chambers. Rats were exposed to ethanol vapors or control chambers for 6 weeks and then withdrawn. Sleep EEG was recorded before exposure (baseline), immediately following exposure, and 5 weeks aft er withdrawal from the ethanol/control chambers. In the ethanol-exposed ani mals, blood ethanol levels averaged 192 mg/dL over 6 weeks of exposure. Chr onic ethanol exposure and withdrawal was not found to affect either slow wa ve sleep latency or slow wave sleep duration; however, overall spectral pow er as well as power in the delta, theta, and beta frequencies were signific antly reduced following chronic exposure (2-4 Hz, [F(1, 17) = 18.11, p = 0. 001], 4-6 Hz, [F(1, 17) = 15.98, p = 0.001], 6-8 Hz [F(1, 17) = 15.52, p = 0.001], 8-16 Hz band [F(1, 17) = 18.73, p < 0.0001], 16-32 Hz [F(1, 17) = 1 0.13, p = 0.005], and 1-50 Hz [F(1, 17) = 17.03, p = 0.001]. After 5 weeks of withdrawal, significant decreases still persisted in the delta and theta frequencies (2-4 Hz [F(1, 16) = 6.21, 0.024], 4-6 Hz [F(1, 16) = 6.26, 0.0 24]. and 6-8 Hz [F(1: 16) = 4.84, p = 0.043]). These findings suggest that spectral analysis of the EEG is a highly sensitive measure of the effects o f ethanol on sleep. These findings additionally demonstrate that chronic et hanol exposure can produce persistent diminution in the systems that genera te cortical slow waves in the rat and thus may provide a model for understa nding the mechanisms underlying sleep disturbances associated with alcoholi sm. (C) 2000 Elsevier Science Inc. All rights reserved.