Reproductive hormone replacement alters sleep in mice

Several studies have reported that reproductive hormones can alter baseline sleep-wake states, however, no studies in mice have examined whether reproductive hormone replacement in adult females and males influences sleep. In this study, we determined whether androgen replacement in males and estrogen replacement in females alter sleep-wake amount and sleep rebound after extended wakefulness. The gonads from adult male and female C57BL/6J mice were removed and animals were implanted with continuous release hormone or placebo pellets. Male mice received testosterone and females received 17 beta-estradiol. Recording electrodes were implanted to monitor sleep-wake states under baseline conditions and in response to 6 h of sleep deprivation. During baseline recording estradiol-treated females exhibited a reduction in NREM sleep amount that was predominant during the dark phase. Testosterone-treated males conversely, exhibited an increase in NREM sleep amount. After sleep deprivation, hormone-treated males and females exhibited similar amounts of recovery sleep however males exhibited slightly more sleep than placebo-treated controls. The results of these experiments demonstrate that the androgens and estrogens are primarily responsible for sex differences in baseline sleep-wake amount but do not have substantial effects on homeostatic sleep rebound after extended wakefulness. (C) 2009 Elsevier Ireland Ltd. All rights reserved.