If norepinephrine levels are high the animal s awake
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The results of our work ( Pompeiano et al. In addition, c-fos and other IEGs function as transcriptional regulators ( Sheng and Greenberg 1990) and may therefore regulate the transcription of a number of target genes that could be directly relevant to the homeostasis and functions of sleep.
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The expression of c-fos can thus serve as a marker of neuronal activity. The best known of such genes, c-fos, shows increased mRNA levels after a few minutes of stimulation, and its protein product, Fos, is synthesized shortly thereafter and can be detected for several hours. Our initial studies focused on the expression of the so-called immediate early genes (IEGs), which are rapidly induced by a large number of extracellular stimuli. Although the characterization of the molecular correlates of sleep, wakefulness, and sleep deprivation is still in progress, it is already apparent that the transition from sleep to waking can affect basic cellular functions such as RNA and protein synthesis, neural plasticity, neurotransmission, and metabolism. Known genes expressed at higher levels in wakefulness and sleep deprivation could be grouped into functional categories: immediate early genes/transcription factors, genes related to energy metabolism, growth factors/adhesion molecules, chaperones/heat shock proteins, vesicle and synapse-related genes, neurotransmitter/hormone receptors, neurotransmitter transporters, enzymes, and others. Almost all the genes upregulated in sleep, and several genes upregulated in wakefulness and sleep deprivation, did not match any known sequence. Most genes were upregulated in wakefulness and sleep deprivation relative to sleep, while only a few were upregulated in sleep relative to wakefulness and sleep deprivation. Out of the ∼10,000 genes screened so far, a small minority ( ∼0.5%) was differentially expressed in the cerebral cortex across behavioral states. In order to determine what molecular changes occur during the sleep-waking cycle, we have recently performed a systematic screening of gene expression in the brain of sleeping, sleep deprived, and spontaneously awake rats.
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The characterization of the molecular correlates of sleep and wakefulness is essential to understand the restorative processes occurring during sleep and the cellular mechanisms underlying sleep regulation.