REM sleep deprivation increases the levels of tyrosine hydroxylase and norepinephrine transporter mRNA in the locus coeruleus

Uncompetitive stimulation of rat brain Na-K ATPase activity by rapid eye movement sleep deprivation

Rapid eye movement sleep deprivation is associated with an increase in Na-K ATPase activity. In order to understand the possible biochemical mechanism of this increase, the kinetics of Na-K ATPase was studied. Although the enzyme activity increased after the deprivation, the catalytic efficiency of the enzyme remained unaltered. The rapid eye movement sleep deprivation increased both the Vmax and the Km suggesting an uncompetitive stimulation of the enzyme. While increase in norepinephrine resulted in an increased Vmax, that of calcium increased the Km. Since an increase in norepinephrine has been suggested after deprivation, the increased Vmax is attributed to increased norepinephrine level following deprivation. However, since rapid eye movement sleep deprivation is reported to be associated with a decrease in calcium levels, the increase in Km following deprivation may be attributed to changes in factor(s) other than calcium.

No evidence of brain cell degeneration after long-term sleep deprivation in rats

Sleep deprivation leads to cognitive impairments in humans and, if sustained for 2-3 weeks in rats, it is invariably fatal. It has been suggested that neural activity associated with waking, if it is not interrupted by periods of sleep, may damage brain cells through excitotoxic or oxidative mechanisms and eventually lead to cell death. To determine whether sustained waking causes brain cell degeneration, three parallel strategies were used. The presence and extent of DNA fragmentation was analyzed with the TUNEL technique on brain sections from rats sleep deprived for various periods of time (from 8 h to 14 days) and from their respective controls. Adjacent sections from the same animals were stained with a newly developed fluorochrome (Fluoro-Jade) specific for degenerating neurons. Finally, total RNA from the cerebral cortex of the same animals was used to determine whether the expression of several stress response genes and apoptosis-related genes is modified after sustained waking. In most long-term sleep deprived rats only a few scattered TUNEL positive nuclei (1-3) were found in any given brain section. The overall number, distribution, and morphology of TUNEL positive cells in long-term sleep deprived rats did not differ significantly from yoked controls, short-term sleep deprived rats, and sleep controls. No evidence of degenerating neurons as detected by Fluoro-Jade was found in any experimental group. mRNA levels of all the stress response genes and apoptosis-related genes tested did not differ between long-term sleep deprived rats and their yoked controls. These results argue against the hypothesis that sustained waking can significantly damage brain cells through excitotoxic or oxidative mechanisms and that massive cell death may explain the fatal consequences of sleep deprivation.

Differences in brain gene expression between sleep and waking as revealed by mRNA differential display and cDNA microarray technology

The consequences of sleep and sleep deprivation at the molecular level are largely unexplored. Knowledge of such molecular events is essential to understand the restorative processes occurring during sleep as well as the cellular mechanisms of sleep regulation. Here we review the available data about changes in neural gene expression across different behavioural states using candidate gene approaches such as in situ hybridization and immunocytochemistry. We then describe new techniques for systematic screening of gene expression in the brain, such as subtractive hybridization, mRNA differential display, and cDNA microarray technology, outlining advantages and disadvantages of these methods. Finally, we summarize our initial results of a systematic screening of gene expression in the rat brain across behavioural states using mRNA differential display and cDNA microarray technology. The expression pattern of approximately 7000 genes was analysed in the cerebral cortex of rats after 3 h of spontaneous sleep, 3 h of spontaneous waking, or 3 h of sleep deprivation. While the majority of transcripts were expressed at the same level among these three conditions, 14 mRNAs were modulated by sleep and waking. Six transcripts, four more expressed in waking and two more expressed in sleep, corresponded to novel genes. The eight known transcripts were all expressed at higher levels in waking than in sleep and included transcription factors and mitochondrial genes. A possible role for these known transcripts in mediating neural plasticity during waking is discussed.

Differences in gene expression during sleep and wakefulness

Compared with our understanding of the electrophysiological correlates of sleep and wakefulness, the search for correlates at the molecular level is still in its infancy. However, the evidence obtained so far supports the hypothesis that reliable molecular correlates do exist. As will be summarized in this review, levels of receptor binding, second messengers and protein phosphorylation differ between sleep and wakefulness. Moreover, compelling data obtained in different animal species suggest that the transition between sleep and wakefulness is accompanied by significant changes in gene expression. Many immediate early genes, transcription factors, plasticity-related genes and mitochondrial genes are expressed at higher levels in wakefulness than in sleep, while a few still unknown genes are up-regulated during sleep. The ongoing systematic screening of gene expression across behavioural states should prove crucial in elucidating the regulatory mechanisms of sleep homeostasis and the functions of sleep.

Transcriptional activity in the brain during sleep deprivation

Molecular biological techniques combined with experimental sleep deprivation have revealed alterations in gene transcriptional activity of several proteins which may mediate the effects of prolonged wakefulness in the brain. During sleep deprivation gene transcription is altered in neuronal systems known to participate in the regulation of vigilance and sleep, ie the norardenergic and cholinergic systems, and several neuropeptides and cytokines. The study of immediate early genes during sleep deprivation has revealed increased transcriptional activity in those brain areas that are active during wakefulness. Systemic search for alterated levels of messenger RNA in sleep-deprived brain has revealed signal transduction proteins and metabolic enzymes which may mediate changes in neuronal function during prolonged wakefulness. The purpose of this article is to give a short overview of those genes whose transcription is affected by sleep deprivation according to the current literature, and to characterize the possible role of these genes in sleep regulation.