Stimulatory role of calcium in rapid eye movement sleep deprivation-induced noradrenaline-mediated increase in Na-K-ATPase activity in rat brain

Abstract

Rapid eye movement (REM) sleep deprivation elevates noradrenaline level, which upon acting on alpha1-adrenoceptors increases Na-K-ATPase activity; however, the detailed intracellular mechanism of action was unknown. Since membrane integrity is crucial for maintaining Na-K-ATPase activity as well as ionic exchange and noradrenaline affects membrane lipid-peroxidation, we proposed that the deprivation might modulate membrane lipid-peroxidation, which would modulate intracellular ionic concentration and thereby increase Na-K-ATPase activity. Hence, in this in vivo and in vitro study, rats were deprived of REM sleep for 4 days by the flowerpot method and suitable control experiments were conducted. The deprivation simultaneously decreased membrane lipid-peroxidation as well as increased Na-K-ATPase activity by its dephosphorylation and all the effects were induced by noradrenaline. Further, in vitro experiments showed that hydrogen peroxide (H₂O₂)-induced enhanced lipid-peroxidation increased synaptosomal calcium (Ca²⁺)-influx, which was also prevented by noradrenaline and nifidipine, an L-type Ca²⁺-channel blocker. Additionally, both nifidipine and cyclopiazonic acid, which have opposite effects on intracellular Ca²⁺-concentration, prevented deprivation induced increased Na-K-ATPase activity. We propose that REM sleep deprivation elevates noradrenaline level in the brain that acting on alpha1-adrenoceptor simultaneously reduces membrane lipid-peroxidation but activates phospholipase-C, resulting in closure of L-type Ca²⁺-channel and releasing membrane bound Ca²⁺; the latter then dephosphorylates Na-K-ATPase, the active form, causing its increased activity.