Sleep responses to light and dark are shaped by early experience.

Light regulates sleep timing through circadian entrapment and by eliciting acute changes in behavior. These behaviors are mediated by the subcortical visual system, retinorecipient nuclei distinct from the geniculocortical system. To test the hypothesis that early visual experience shapes light regulation of behavior, the authors recorded sleep in albino rats reared in continuous dark, continuous light, or a 12-hr light-dark cycle. Dark rearing strengthened and light rearing weakened acute responses to light, including light modulation of REM sleep, a marker for pretectal function in albino rats. However, neither dark nor light rearing altered daily amounts of wakefulness, non-REM sleep, or REM sleep. Thus, light and dark rearing might differentially affect the balance between acute and circadian responses to light that, in concert, govern sleep timing.

REM sleep deprivation induces changes in coping responses that are not reversed by amphetamine.

STUDY OBJECTIVE: Although sleep deprivation often occurs during stressful or threatening situations, the effects of sleep loss on defensive and coping behaviors are not well known. The purpose of the present study was to measure the effects of selective rapid eye movement (REM) sleep deprivation (RSD) on responses elicited by threatening situations and to assess the extent to which RSD-induced changes are reversed by amphetamine. DESIGN: Animals were divided into 3 groups; home-cage control, apparatus control, and REM sleep-deprived groups. The flowerpot method was used to produce RSD for up to 5 days. One set of rats was tested in the elevated plus maze, open field, shock-induced freezing, and analgesia tests. A second set of rats was evaluated for locomotor activity. A third set of animals was assessed in the defensive burying test. For the amphetamine studies, groups of home-cage control and REM sleep-deprived rats received an intraperitoneal injection of amphetamine prior to administration of the shock-induced freezing test or the defensive burying test. SETTING: Sleep Research Laboratory at UW-Madison. PARTICIPANTS AND INTERVENTIONS: 186 male Long-Evans rats approximately 3 months old. MEASUREMENTS AND RESULTS: RSD increased the proportion of time spent in open arms of the elevated plus maze and center of the open field, decreased freezing time, and reduced defensive burying. Amphetamine did not reverse RSD-induced changes in freezing or burying responses. CONCLUSIONS: RSD causes widespread abnormalities in coping and defensive responses in threatening situations; these deficits are not reversed and, in some cases, may be exacerbated by amphetamine.