Contribution of transcriptional and translational mechanisms to the recovery aspect of sleep regulation

Wakefulness/sleep architecture and electroencephalographic activity in mice lacking the translational repressor 4E-BP1 or 4E-BP2

Sleep and sleep loss are affecting protein synthesis in the brain, but the contribution of translational control to wakefulness and sleep regulation remains poorly understood. Here, we studied the role of two suppressors of protein synthesis, the eukaryotic translation initiation factor 4E-binding proteins 1 and 2 (4E-BP1 and 4E-BP2), in sleep architecture and electroencephalographic (EEG) activity as well as in the EEG and molecular responses to acute sleep loss. The EEG of mice mutant for the genes encoding 4E-BP1 or 4E-BP2 (Eif4ebp1 and Eif4ebp2 knockout [KO] mice) was recorded under undisturbed conditions and following a 6-hour sleep deprivation (SD). The effect of SD on the expression of genes known to respond to SD was also measured in the prefrontal cortex of Eif4ebp1 and Eif4ebp2 KO mice. Eif4ebp1 KO mice differed from wild-type mice in parameters of wakefulness and sleep quantity and quality, and more subtly in the gene expression response to SD. For instance, Eif4ebp1 KO mice spent more time in slow-wave sleep (SWS) and showed altered baseline 24-h time courses of SWS delta (1-4 Hz) activity and sigma (10-13 Hz) activity. Eif4ebp2 KO mice differed from wild-type mice only for wakefulness and sleep quality, expressing changes in EEG spectral activity generally revealed during and after SD. These findings suggest different roles of effectors of translational control in the regulation of wakefulness and sleep and of synchronized cortical activity.

PKC in rat dorsal raphe nucleus plays a key role in sleep-wake regulation

Studies suggest a tight relationship between protein kinase C (PKC) and circadian clock. However, the role of PKC in sleep-wake regulation remains unclear. The present study was conducted to investigate the role of PKC signaling in sleep-wake regulation in the rat. Our results showed that the phosphorylation level of PKC in dorsal raphe nucleus (DRN) was decreased after 6h sleep deprivation, while no alterations were found in ventrolateral preoptic nucleus (VLPO) or locus coeruleus (LC). Microinjection of a pan-PKC inhibitor, chelerythrine chloride (CHEL, 5 or 10nmol), into DRN of freely moving rats promoted non rapid eye movement sleep (NREMS) without influences on rapid eye movement sleep (REMS). Especially, CHEL application at 5nmol increased light sleep (LS) time while CHEL application at 10nmol increased slow wave sleep (SWS) time and percentage. On the other hand, microinjection of CaCl2 into DRN not only increased the phosphorylation level of PKC, but also reduced NREMS time, especially SWS time and percentage. While CHEL abolished the inhibitory effect of CaCl2 on NREMS and SWS. These data provide the first direct evidence that inhibition of intracellular PKC signaling in DRN could increase NREMS time including SWS time and percentage, while activation of PKC could suppress NREMS and reduce SWS time and percentage. These novel findings further our understanding of the basic cellular and molecular mechanisms of sleep-wake regulation.