Rapid eye movement sleep deprivation increases chloride-sensitive Mg-ATPase activity in the rat brain

Acute 2-phenyl-3-(phenylselanyl)benzofuran treatment reverses the neurobehavioral alterations induced by sleep deprivation in mice

Sleep is a fundamental state for maintaining the organism homeostasis. Disruptions in sleep patterns predispose to the appearance of memory impairments and mental disorders, including depression. Recent pre-clinical studies have highlighted the antidepressant-like properties of the synthetic compound 2-phenyl-3-(phenylselanyl)benzofuran (SeBZF1). To further investigate the neuromodulatory effects of SeBZF1, this study aimed to assess its therapeutic efficacy in ameliorating neurobehavioral impairments induced by sleep deprivation (SD) in mice. For this purpose, a method known as multiple platforms over water was used to induce rapid eye movement (REM) SD. Two hours after acute SD (24 h), male Swiss mice received a single treatment of SeBZF1 (5 mg/kg, intragastric route) or fluoxetine (a positive control, 20 mg/kg, intraperitoneal route). Subsequently, behavioral tests were conducted to assess spontaneous motor function (open-field test), depressive-like behavior (tail suspension test), and memory deficits (Y-maze test). Brain structures were utilized to evaluate oxidative stress markers, monoamine oxidase (MAO) and acetylcholinesterase (AChE) activities. Our findings revealed that SD animals displayed depressive-like behavior and memory impairments, which were reverted by SeBZF1 and fluoxetine treatments. SeBZF1 also reverted the increase in lipoperoxidation levels and glutathione peroxidase activity in the pre-frontal cortex in mice exposed to SD. Besides, the increase in hippocampal AChE activity induced by SD was overturned by SeBZF1. Lastly, cortical MAO-B activity was reestablished by SeBZF1 in mice that underwent SD. Based on the main findings of this study, it can be inferred that the compound SeBZF1 reverses the neurobehavioral alterations induced by sleep deprivation in male Swiss mice.

Rapid eye movement sleep loss associated cytomorphometric changes and neurodegeneration

Rapid eye movement sleep (REMS) is essential for leading normal healthy living at least in higher-order mammals, including humans. In this review, we briefly survey the available literature for evidence linking cytomorphometric changes in the brain due to loss of REMS. As a mechanism of action, we add evidence that REMS loss elevates noradrenaline (NA) levels in the brain, which affects neuronal cytomorphology. These changes may be a compensatory mechanism as the changes return to normal after the subjects recover from the loss of REMS or if during REMS deprivation, the subjects are treated with NA-adrenoceptor antagonist prazosin (PRZ). We had proposed earlier that one of the fundamental functions of REMS is to maintain the level of NA in the brain. We elaborate on this idea to propose that if REMS loss continues without recovery, the sustained level of NA breaks down neurophysiologically active compensatory mechanism/s starting with changes in the neuronal cytomorphology, followed by their degeneration, leading to acute and chronic pathological conditions. Identification of neuronal cytomorphological changes could prove to be of significance for predicting future neuronal (brain) damage as well as an indicator for REMS health. Although current brain imaging techniques may not enable us to visualize changes in neuronal cytomorphology, given the rapid technological progress including use of artificial intelligence, we are optimistic that it may be a reality soon. Finally, we propose that maintenance of optimum REMS must be considered a criterion for leading a healthy life.

Rapid Eye Movement Sleep Deprivation Induces Neuronal Apoptosis by Noradrenaline Acting on Alpha1 Adrenoceptor and by Triggering Mitochondrial Intrinsic Pathway

Many neurodegenerative disorders are associated with rapid eye movement sleep (REMS) loss; however, the mechanism was unknown. As REMS loss elevates noradrenaline (NA) level in the brain as well as induces neuronal apoptosis and degeneration, in this study, we have delineated the intracellular molecular pathway involved in REMS deprivation (REMSD)-associated NA-induced neuronal apoptosis. Rats were REMS deprived for 6 days by the classical flower pot method; suitable controls were conducted and the effects on apoptosis markers evaluated. Further, the role of NA was studied by one, intraperitoneal (i.p.) injection of NA-ergic alpha1 adrenoceptor antagonist prazosin (PRZ) and two, by downregulation of NA synthesis in locus coeruleus (LC) neurons by local microinjection of tyrosine hydroxylase siRNA (TH-siRNA). Immunoblot estimates showed that the expressions of proapoptotic proteins viz. Bcl2-associated death promoter protein, apoptotic protease activating factor-1 (Apaf-1), cytochrome c, caspase9, caspase3 were elevated in the REMS-deprived rat brains, while caspase8 level remained unaffected; PRZ treatment did not allow elevation of these proapoptotic factors. Further, REMSD increased cytochrome c expression, which was prevented if the NA synthesis from the LC neurons was blocked by microinjection of TH-siRNA in vivo into the LC during REMSD in freely moving normal rats. Mitochondrial damage was re-confirmed by transmission electron microscopy, which showed distinctly swollen mitochondria with disintegrated cristae, chromosomal condensation, and clumping along the nuclear membrane, and all these changes were prevented in PRZ-treated rats. Combining findings of this study along with earlier reports, we propose that upon REMSD NA level increases in the brain as the LC, NA-ergic REM-OFF neurons do not cease firing and TH is upregulated in those neurons. This elevated NA acting on alpha1 adrenoceptors damages mitochondria causing release of cytochrome c to activate intrinsic pathway for inducing neuronal apoptosis in REMS-deprived rat brain.

REM sleep loss increases brain excitability: role of noradrenaline and its mechanism of action

Ever since the discovery of rapid eye movement sleep (REMS), studies have been undertaken to understand its necessity, function and mechanism of action on normal physiological processes as well as in pathological conditions. In this review, first, we briefly surveyed the literature which led us to hypothesise REMS maintains brain excitability. Thereafter, we present evidence from in vivo and in vitro studies tracing behavioural to cellular to molecular pathways showing REMS deprivation (REMSD) increases noradrenaline level in the brain, which stimulates neuronal Na-K ATPase, the key factor for maintaining neuronal excitability, the fundamental property of a neuron for executing brain functions; we also show for the first time the role of glia in maintaining ionic homeostasis in the brain. As REMSD exerts a global effect on most of the physiological processes regulated by the brain, we propose that REMS possibly serves a housekeeping function in the brain. Finally, subject to confirmation from clinical studies, based on the results reviewed here, it is being proposed that the subjects suffering from REMS loss may be effectively treated by reducing either noradrenaline level or Na-K ATPase activity in the brain.

Cytomorphometric changes in the dorsal raphe neurons after rapid eye movement sleep deprivation are mediated by noradrenalin in rats

OBJECTIVES

This study was carried out to investigate the effect of rapid eye movement sleep (REMS) deprivation (REMSD) on the cytomorphology of the dorsal raphe (DR) neurons and to evaluate the possible role of REMSD-induced increased noradrenalin (NA) in mediating such effects.

METHODS

Rats were REMS deprived by the flowerpot method; free moving normal home cage rats, large platform and post REMS-deprived recovered rats were used as controls. Further, to evaluate if the effects were induced by NA, separate sets of experimental rats were treated (i.p.) with α1-adrenoceptor antagonist, prazosin (PRZ). Histomorphometric analysis of DR neurons in stained brain sections were performed in experimental and control rats; neurons in inferior colliculus (IC) served as anatomical control.

RESULTS

The mean size of DR neurons was larger in REMSD group compared to controls, whereas, neurons in the recovered group of rats did not significantly differ than those in the control animals. Further, mean cell size in the post-REMSD PRZ-treated animals was comparable to those in the control groups. IC neurons were not affected by REMSD.

CONCLUSIONS

REMS loss has been reported to impair several physiological, behavioral and cellular processes. The mean size of the DR neurons was larger in the REMS deprived group of rats than those in the control groups; however, in the REMS deprived and prazosin treated rats the size was comparable to the normal rats. These results showed that REMSD induced increase in DR neuronal size was mediated by NA acting on α1-adrenoceptor. The findings suggest that the sizes of DR neurons are sensitive to REMSD, which if not compensated could lead to neurodegeneration and associated disorders including memory loss and Alzheimer's disease.

Cytomorphometric changes in rat brain neurons after rapid eye movement sleep deprivation

Rapid eye movement sleep plays a vital role in the survival of animals. Its deprivation causes alterations in brain functions and behaviors including activities of important enzymes, neurotransmitter levels, impairment of neural excitability and memory consolidation. However, there was a lack of knowledge regarding the effects of rapid eye movement sleep deprivation on neuronal morphology that may get affected much earlier than any permanent damage to the neurons. In the present study, some of these issues have been addressed by studying the effects of rapid eye movement sleep deprivation on various morphological parameters viz. neuronal perimeter, area and shape of neurons located in brain areas known to regulate rapid eye movement sleep and as a control in other brain areas which do not regulate rapid eye movement sleep. The results showed that rapid eye movement sleep deprivation differentially affected neurons depending on their physiological correlates of rapid eye movement sleep and neurotransmitter content. The effects could be reversed if the animals were allowed to recover from rapid eye movement sleep loss or by applying alpha1-adrenergic antagonist, prazosin. The findings in rats support reported data and help explaining previous observations.

Role of norepinephrine in the regulation of rapid eye movement sleep

Sleep and wakefulness are instinctive behaviours that are present across the animal species. Rapid eye movement (REM) sleep is a unique biological phenomenon expressed during sleep. It evolved about 300 million years ago and is noticed in the more evolved animal species. Although it has been objectively identified in its present characteristic form about half a century ago, the mechanics of how REM is generated, and what happens upon its loss are not known. Nevertheless, extensive research has shown that norepinephrine plays a crucial role in its regulation. The present knowledge that has been reviewed in this manuscript suggests that neurons in the brain stem are responsible for controlling this state and presence of excess norepinephrine in the brain does not allow its generation. Furthermore, REM sleep loss increases levels of norepinephrine in the brain that affects several factors including an increase in Na-K ATPase activity. It has been argued that such increased norepinephrine is ultimately responsible for REM sleep deprivation, associated disturbances in at least some of the physiological conditions leading to alteration in behavioural expression and settling into pathological conditions.

The neurophysiology of sleep and waking: intracerebral connections, functioning and ascending influences of the medulla oblongata

This paper focuses on the successive historical papers related to medulla oblongata (M.O.) intracerebral connections, its activities and ascending influences regulating sleep waking behavior. The M.O. certainly influences the quantitative and qualitative processes of waking. However, its neurophysiological properties are often concealed by those of the upper-situated brain stem structures. The M.O., particularly the solitary tract nucleus, is involved in sleep-inducing processes. This nucleus seem to act as a deactivating system of the above situated reticular formation, but it also impacts directly on the thalamocortical slow wave and spindle-inducing processes. The M.O. is significantly involved in paradoxical sleep mechanisms. Indeed, the mesopontine executive centers are unable to induce paradoxical sleep without the M.O. Moreover, stimulation of the solitary tract nucleus afferents can induce paradoxical sleep, and the M.O. metabolic functioning is specifically disturbed by paradoxical sleep deprivation. Finally. there seems to be a paradoxical sleep Zeitgeber. Our current knowledge shows that this lowest brain stem level is crucial for sleep waking mechanisms. It will undoubtedly be further highlighted by future electrophysiologial and neurochemical studies.

Alterations in synaptosomal calcium concentrations after rapid eye movement sleep deprivation in rats

Rapid eye movement sleep deprivation alters behavioral and physiological, as well as cellular functioning and responsiveness. Since intracellular calcium concentration plays an important role in regulating cellular functions, it was hypothesized that such deprivation might induce changes in intracellular calcium concentration. Therefore, in this study, rats were deprived of rapid eye movement sleep by the flower-pot technique, and total, bound and free calcium concentrations were estimated in synaptosomal preparations from the cerebrum, cerebellum, brainstem, midbrain, pons and medulla. Rapid eye movement sleep deprivation was continued for two or four days and suitable control experiments were conducted to rule out the effects of non-specific factors. Total calcium concentration increased in the brainstem but showed a decrease in the cerebellum and cerebrum. After four days deprivation, the free calcium concentration always decreased; however, the bound calcium concentration decreased in the cerebrum and cerebellum but increased in the brainstem. After two days' deprivation, the medulla was the only region where the bound calcium increased while the free form decreased; only the free form decreased in the pons, while the midbrain was never affected. The results suggest that there was a net efflux of calcium in the cerebellum and cerebrum, but a net influx in the brainstem. The findings support our hypothesis and help to explain earlier observations. Since it is known that calcium plays an important role in cellular functioning, these changes in calcium concentration may be the underlying mechanism for rapid eye movement sleep deprivation-induced cellular expressions and behavior of neurons.

Rapid eye movement sleep deprivation decreases membrane fluidity in the rat brain

In this study we examined the effects of rapid eye movement sleep (REMS) deprivation on synaptosomal and microsomal membrane fluidity by studying 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization in control as well as REMS-deprived rats. The flower pot technique was used to perform 24, 48 and 96 h REMS deprivation. Suitable control experiments were carried out to rule out the nonspecific effects. The results showed that DPH fluorescence polarization increased both in the microsome as well as in the synaptosome in REMS-deprived animals, except in the cerebellum, indicating that there was a generalized decrease in membrane fluidity in the rat brain. The alterations in membrane fluidity returned to baseline upon recovery from REMS deprivation. Control experiments suggested that the alterations were primarily caused by REMS deprivation and not due to nonspecific effects. This finding supports REMS deprivation induced other changes reported earlier. This increase in membrane rigidity could be at least one of the possibilities for REMS loss induced alterations in physiological phenomena including membrane bound enzyme activities and receptor densities.

Possible mechanism of rapid eye movement sleep deprivation induced increase in Na-K ATPase activity

Rapid eye movement sleep deprivation increases Na-K ATPase activity and decreases aminergic neuronal firing rate as well as norepinephrine degrading enzyme, monoamine oxidase, activity. On the other hand, norepinephrine is known to increase Na-K ATPase activity. Hence, this study was conducted to find if the deprivation induced increase in Na-K ATPase activity is mediated by norepinephrine. Rapid eye movement sleep deprived rats were injected with either alpha-1 or beta adrenoceptor antagonist or alpha-2 adrenoceptor agonist and after 8 h the Na-K ATPase activity of the brain was estimated. In an attempt to simulate in vivo conditions, norepinephrine was added to an in vitro brain homogenate preparation in the presence or absence of alpha or beta adrenoceptor blockers and the enzyme activity was estimated. The results showed that the enzyme activity was decreased by alpha-1 antagonist as well as by alpha-2 agonist treatment in in vivo preparations. Norepinephrine increased enzyme activity in the in vitro preparation and the increase was prevented by the alpha-1 antagonist. The results of this study suggest that rapid eye movement sleep deprivation induced increase in Na-K ATPase activity may be mediated by norepinephrine acting on either alpha-1 and/or alpha-2 receptors.