Calcium/Calmodulin Kinase II in the Pedunculopontine Tegmental Nucleus Modulates the Initiation and Maintenance of Wakefulness

Abstract

The pedunculopontine tegmentum nucleus (PPT) is critically involved in the regulation of wakefulness (W) and rapid eye movement (REM) sleep, but our understanding of the mechanisms of this regulation remains incomplete. The present study was designed to determine the role of PPT intracellular calcium/calmodulin kinase (CaMKII) signaling in the regulation of W and sleep. To achieve this aim, three different concentrations (0.5, 1.0, and 2.0 nmol) of the CaMKII activation inhibitor, KN-93, were microinjected bilaterally (100 nl/site) into the PPT of freely moving rats, and the effects on W, slow-wave sleep (SWS), REM sleep, and levels of phosphorylated CaMKII (pCaMKII) expression in the PPT were quantified. These effects, which were concentration-dependent and affected wake–sleep variables for 3 h, resulted in decreased W, due to reductions in the number and duration of W episodes; increased SWS and REM sleep, due to increases in episode duration; and decreased levels of pCaMKII expression in the PPT. Regression analyses revealed that PPT levels of pCaMKII were positively related with the total percentage of time spentin W (R2 = 0.864; n = 28 rats; p < 0.001) and negatively related with the total percentage of time spentin sleep (R2 = 0.863; p < 0.001). These data provide the first direct evidence that activation of intracellular CaMKII signaling in the PPT promotes W and suppresses sleep. These findings are relevant for designing a drug that could treat excessive sleepiness by promoting alertness.

The primate pedunculopontine nucleus region: towards a dual role in locomotion and waking state

“…More recently, in naturally sleeping/waking rodent, PPN cholinergic and putative glutamatergic neurons were also found to increase their FR before cortical activation (Boucetta et al 2014) similar to what we observed in the present study in behaving NHP. This is in accordance with an active role of these MRF neurons in the generating mechanisms of the wakefulness/REM cycle in the rat (Datta and Siwek 2002;Datta et al 2011). Interestingly, it has been shown that lesion of the cholinergic PPN neurons in a NHP model of PD only induced transient (up to 3 weeks post lesion) sleep disorders and emergence of cortical delta wave activity during waking (Belaid et al 2014) while unspecific lesion of the PPN in rat had no major effect on sleep architecture (Deurveilher and Hennevin 2001) possibly because other pathways also involved in arousal, e.g., orexin, histamine, were still intact.…”

High-threshold Ca2+channels behind gamma band activity in the pedunculopontine nucleus (PPN)

“…For example, the CaMKII activation inhibitor, KN‐93, microinjected into the PPN of freely moving rats (in vivo) resulted in decreased waking but not REM sleep (Datta et al. ). We have shown (in vitro) that beta/gamma band oscillations in PPN neurons are blocked by superfusion of KN‐93 (Garcia‐Rill et al.…”

REM Sleep Regulating Mechanisms in the Cholinergic Cell Compartment of the Brainstem

“…Collectively, the results of this study suggest that the increased CaMKII activity within the PPT neurons is associated with increased wakefulness at the expense of REM sleep, and this process is accomplished through the activation of a specific gene expression profile 52 . Moreover, a more recent study that utilized a combination of behavioral, pharmacological, and molecular techniques has provided direct evidence that CaMKII intracellular signaling within PPT neurons is indeed involved in the induction and maintenance of wakefulness that ultimately terminates REM sleep 53 . Since within the normal sleep-wake cycle, the end of REM sleep corresponds with the beginning of wakefulness —a transition that requires increased PPT neuronal activity — and also based on the results discussed above, it is therefore reasonable to suggest that increased CaMKII activity in the PPT neurons is the intracellular signaling mechanism for the behavioral transition from REM sleep to wakefulness (Fig.…”

“…These differential interactions of numerous signaling pathways regulate the distribution, duration, intensity and specificity of the cellular response 65,69,78–82 . Recent studies have shown that the activation of the PKA signaling pathway in PPT cells promotes REM sleep 40,41,43 , whereas activation of the CaMKII pathway in PPT cells promotes wakefulness by suppressing REM sleep 52,53 . Additionally, activation of the ERK1/2 signaling pathway in PPT cells promotes both SWS and REM sleep by suppressing wakefulness 71 .…”