REM sleep deprivation reduces auditory evoked inhibition of dorsolateral pontine neurons

REM Sleep Loss-Induced Elevated Noradrenaline Plays a Significant Role in Neurodegeneration: Synthesis of Findings to Propose a Possible Mechanism of Action from Molecule to Patho-Physiological Changes

Wear and tear are natural processes for all living and non-living bodies. All living cells and organisms are metabolically active to generate energy for their routine needs, including for survival. In the process, the cells are exposed to oxidative load, metabolic waste, and bye-products. In an organ, the living non-neuronal cells divide and replenish the lost or damaged cells; however, as neuronal cells normally do not divide, they need special feature(s) for their protection, survival, and sustenance for normal functioning of the brain. The neurons grow and branch as axons and dendrites, which contribute to the formation of synapses with near and far neurons, the basic scaffold for complex brain functions. It is necessary that one or more basic and instinct physiological process(es) (functions) is likely to contribute to the protection of the neurons and maintenance of the synapses. It is known that rapid eye movement sleep (REMS), an autonomic instinct behavior, maintains brain functioning including learning and memory and its loss causes dysfunctions. In this review we correlate the role of REMS and its loss in synaptogenesis, memory consolidation, and neuronal degeneration. Further, as a mechanism of action, we will show that REMS maintains noradrenaline (NA) at a low level, which protects neurons from oxidative damage and maintains neuronal growth and synaptogenesis. However, upon REMS loss, the level of NA increases, which withdraws protection and causes apoptosis and loss of synapses and neurons. We propose that the latter possibly causes REMS loss associated neurodegenerative diseases and associated symptoms.

REM sleep loss-induced elevated noradrenaline could predispose an individual to psychosomatic disorders: a review focused on proposal for prediction, prevention, and personalized treatment

Historically and traditionally, it is known that sleep helps in maintaining healthy living. Its duration varies not only among individuals but also in the same individual depending on circumstances, suggesting it is a dynamic and personalized physiological process. It has been divided into rapid eye movement sleep (REMS) and non-REMS (NREMS). The former is unique that adult humans spend the least time in this stage, when although one is physically asleep, the brain behaves as if awake, the dream state. As NREMS is a pre-requisite for appearance of REMS, the latter can be considered a predictive readout of sleep quality and health. It plays a protective role against oxidative, stressful, and psychopathological insults. Several modern lifestyle activities compromise quality and quantity of sleep (including REMS) affecting fundamental physiological and psychopathosomatic processes in a personalized manner. REMS loss-induced elevated brain noradrenaline (NA) causes many associated symptoms, which are ameliorated by preventing NA action. Therefore, we propose that awareness about personalized sleep hygiene (including REMS) and maintaining optimum brain NA level should be of paramount significance for leading physical and mental well-being as well as healthy living. As sleep is a dynamic, multifactorial, homeostatically regulated process, for healthy living, we recommend addressing and treating sleep dysfunctions in a personalized manner by the health professionals, caregivers, family, and other supporting members in the society. We also recommend that maintaining sleep profile, optimum level of NA, and/or prevention of elevation of NA or its action in the brain must be seriously considered for ameliorating lifestyle and REMS disturbance-associated dysfunctions.

Relevance of deprivation studies in understanding rapid eye movement sleep

Rapid eye movement sleep (REMS) is a unique phenomenon essential for maintaining normal physiological processes and is expressed at least in species higher in the evolution. The basic scaffold of the neuronal network responsible for REMS regulation is present in the brainstem, which may be directly or indirectly influenced by most other physiological processes. It is regulated by the neurons in the brainstem. Various manipulations including chemical, elec-trophysiological, lesion, stimulation, behavioral, ontogenic and deprivation studies have been designed to understand REMS genesis, maintenance, physiology and functional significance. Although each of these methods has its significance and limitations, deprivation studies have contributed significantly to the overall understanding of REMS. In this review, we discuss the advantages and limitations of various methods used for REMS deprivation (REMSD) to understand neural regulation and physiological significance of REMS. Among the deprivation strategies, the flowerpot method is by far the method of choice because it is simple and convenient, exploits physiological parameter (muscle atonia) for REMSD and allows conducting adequate controls to overcome experimental limitations as well as to rule out nonspecific effects. Notwithstanding, a major criticism that the flowerpot method faces is that of perceived stress experienced by the experimental animals. Nevertheless, we conclude that like most methods, particularly for in vivo behavioral studies, in spite of a few limitations, given the advantages described above, the flowerpot method is the best method of choice for REMSD studies.

Enhanced emotional reactivity after selective REM sleep deprivation in humans: an fMRI study

Converging evidence from animal and human studies suggest that rapid eye movement (REM) sleep modulates emotional processing. The aim of the present study was to explore the effects of selective REM sleep deprivation (REM-D) on emotional responses to threatening visual stimuli and their brain correlates using functional magnetic resonance imaging (fMRI). Twenty healthy subjects were randomly assigned to two groups: selective REM-D, by awakening them at each REM sleep onset, or non-rapid eye movement sleep interruptions (NREM-I) as control for potential non-specific effects of awakenings and lack of sleep. In a within-subject design, a visual emotional reactivity task was performed in the scanner before and 24 h after sleep manipulation. Behaviorally, emotional reactivity was enhanced relative to baseline (BL) in the REM deprived group only. In terms of fMRI signal, there was, as expected, an overall decrease in activity in the NREM-I group when subjects performed the task the second time, particularly in regions involved in emotional processing, such as occipital and temporal areas, as well as in the ventrolateral prefrontal cortex, involved in top-down emotion regulation. In contrast, activity in these areas remained the same level or even increased in the REM-D group, compared to their BL level. Taken together, these results suggest that lack of REM sleep in humans is associated with enhanced emotional reactivity, both at behavioral and neural levels, and thus highlight the specific role of REM sleep in regulating the neural substrates for emotional responsiveness.

Neurochemical and electrophysiological changes induced by paradoxical sleep deprivation in rats

The present study aims to investigate the effects of paradoxical sleep deprivation (PSD) on the waking EEG and amino acid neurotransmitters in the hippocampus and cortex of rats. Animals were deprived of paradoxical sleep for 72h by using the multiple platform method. The EEG power spectral analysis was carried out to assess the brain's electrophysiological changes due to sleep deprivation. The concentrations of amino acid neurotransmitters were assessed in the hippocampus and cortex using HPLC. Control data showed slight differences from normal animals in the delta, theta and alpha waves while an increase in the beta wave was obtained. After 24h of PSD, delta relative power increased and the rest of EEG wave's power decreased with respect to control. After 48h and 72h the spectral power analysis showed non-significant changes to control. The amino acid neurotransmitter analysis revealed a significant increase in cortical glutamate, glycine and taurine levels while in the hippocampus, glutamate, aspartate, glutamine and glycine levels increased significantly. Both the waking EEG and neurotransmitter analyses suggest that PSD induced neurochemical and electrophysiological changes that may affect brain proper functionality.

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.

Increased apoptosis in rat brain after rapid eye movement sleep loss

Rapid eye movement (REM) sleep loss impairs several physiological, behavioral and cellular processes; however, the mechanism of action was unknown. To understand the effects of REM sleep deprivation on neuronal damage and apoptosis, studies were conducted using multiple apoptosis markers in control and experimental rat brain neurons located in areas either related to or unrelated to REM sleep regulation. Furthermore, the effects of REM sleep deprivation were also studied on neuronal cytoskeletal proteins, actin and tubulin. It was observed that after REM sleep deprivation a significantly increased number of neurons in the rat brain were positive to apoptotic markers, which however, tended to recover after the rats were allowed to undergo REM sleep; the control rats were not affected. Further, it was also observed that REM sleep deprivation decreased amounts of actin and tubulin in neurons confirming our previous reports of changes in neuronal size and shape after such deprivation. These findings suggest that one of the possible functions of REM sleep is to protect neurons from damage and apoptosis.

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.

Increased turnover of Na-K ATPase molecules in rat brain after rapid eye movement sleep deprivation

It has been shown that rapid eye movement (REM) sleep deprivation increases Na-K ATPase activity. Based on kinetic study, it was proposed that increased activity was due to enhanced turnover of enzyme molecules. To test this, anti-alpha1 Na-K ATPase monoclonal antibody (mAb 9A7) was used to label Na-K ATPase molecules. These labeled enzymes were quantified on neuronal membrane by two methods: histochemically on neurons in tissue sections from different brain areas, and by Western blot analysis in control and REM sleep-deprived rat brains. The specific enzyme activity was also estimated and found to be increased, as in previous studies. The results confirmed our hypothesis that after REM sleep deprivation, increased Na-K ATPase activity was at least partly due to increased turnover of Na-K ATPase molecules in the rat brain.

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.

Uncompetitive stimulation of rat brain Na-K ATPase activity by rapid eye movement sleep deprivation

Rapid eye movement sleep deprivation is associated with an increase in Na-K ATPase activity. In order to understand the possible biochemical mechanism of this increase, the kinetics of Na-K ATPase was studied. Although the enzyme activity increased after the deprivation, the catalytic efficiency of the enzyme remained unaltered. The rapid eye movement sleep deprivation increased both the Vmax and the Km suggesting an uncompetitive stimulation of the enzyme. While increase in norepinephrine resulted in an increased Vmax, that of calcium increased the Km. Since an increase in norepinephrine has been suggested after deprivation, the increased Vmax is attributed to increased norepinephrine level following deprivation. However, since rapid eye movement sleep deprivation is reported to be associated with a decrease in calcium levels, the increase in Km following deprivation may be attributed to changes in factor(s) other than calcium.

Norepinephrine induced alpha-adrenoceptor mediated increase in rat brain Na-K ATPase activity is dependent on calcium ion

It has been reported that norepinephrine increases Na-K ATPase activity by acting on alpha-1 adrenoceptors. The mechanism of such an increase was investigated. The norepinephrine induced increase in synaptosomal Na-K ATPase activity was prevented by pretreating the rat brain homogenate with either EDTA, a divalent cation chelator or prazosin, an alpha-1 adrenoceptor blocker. The norepinephrine and EGTA increased the Na-K ATPase activity in the synaptosome prepared from rat brain homogenate untreated with EDTA. The EGTA was ineffective in stimulating the enzyme activity if the synaptosome was prepared from homogenate treated with norepinephrine. However, the EGTA was effective in increasing the enzyme activity if the synaptosome was prepared from the homogenate treated with norepinephrine in the presence of prazosin. Thus, norepinephrine did not increase the Na-K ATPase activity in the presence of EDTA or alpha-1 adrenoceptor blocker. Similarly, the Ca++ chelator, EGTA, could not increase the enzyme activity if the homogenate was pretreated with norepinephrine alone. However, if norepinephrine action was blocked by alpha-1 antagonist prazosin, EGTA increased the enzyme activity possibly by chelation of Ca++. Further, chlorotetracycline fluorescence study showed that norepinephrine removes membrane bound Ca++. Thus, it is likely that norepinephrine acts on adrenoceptors and removes membrane bound Ca++ and thereby increases the Na-K ATPase activity in the synaptosome.

Comparison of Na-K ATPase activity in rat brain synaptosome under various conditions

Rapid eye movement (REM) sleep deprivation alters neuronal excitability possibly by increasing Na-K ATPase activity. The enzyme activity is known to be affected by norepinephrine as well as calcium (Ca++) and both are affected by REM sleep deprivation. Before studying its molecular mechanism of action, synaptosomal Na-K ATPase activity was estimated under various conditions. The enzyme activity in synaptosome increased after lysis and in the presence of EDTA. The increase in the lysed preparation was possibly because almost all the active sites of the enzyme molecules were exposed to express their activity, unlike unlysed preparation where half are likely to be inside out. EDTA possibly increased the enzyme activity by chelating the Ca++ which is known to have an inhibitory effect on the enzyme activity. Also, the REM sleep deprivation induced increase in the enzyme activity was observed in lysed preparations and in the presence of EDTA only. These observations fit with the existing knowledge, however, the molecular mechanism of the increase needs to be investigated.

Heterogeneous effects of rapid eye movement sleep deprivation on binding to alpha- and beta-adrenergic receptor subtypes in rat brain

Quantitative receptor autoradiography was used to map alterations in binding to alpha1-, alpha2-, beta1- and beta2-adrenergic receptors throughout the brain of rats deprived of rapid eye movement sleep for 96 h. Binding of [3H]prazosin to alpha1 sites, while not significantly different in any of 46 brain regions examined, showed a clear overall tendency towards decreased values after sleep deprivation. [3H]UK-14,314-labeled alpha2 binding sites were not significantly affected by sleep deprivation in any of 91 brain regions analysed, despite a trend towards increased values. In contrast, beta-adrenergic binding was significantly reduced throughout the brain. Binding to beta1 sites labeled by [125I]iodopindolol in the presence of ICI-11855 was significantly reduced in 13 of 69 brain areas examined; binding to beta2 sites labeled by [125I]iodopindolol in the presence of CGP-20712A was likewise reduced throughout the brain and significantly so in 25 of the 72 brain areas analysed. Rank ordering of the binding changes indicated that reductions in beta1 vs beta2 binding were maximal in different brain areas. This pattern of results may reflect a particular configuration of effects specifically associated with sleep loss stress. The results are consistent with evidence of persisting noradrenergic cell activity during sleep deprivation. The observed heterogeneity of effects suggests that not all norepinephrine receptors are equally affected by rapid eye movement sleep deprivation.

REM sleep deprivation increases the levels of tyrosine hydroxylase and norepinephrine transporter mRNA in the locus coeruleus

The present study was conducted to determine the effects of REM sleep deprivation on the levels of tyrosine hydroxylase (TH) and norepinephrine transporter (NET) mRNA in the locus coeruleus (LC) of rats. The animals were deprived of REM sleep for 1, 3 or 5 days, then killed and changes in the mRNA levels were determined using in situ hybridization. The levels of both TH and NET mRNA increased in animals deprived of REM sleep for 3 days or longer whereas no change in these messages were observed in the LC of control animals. REM sleep deprivation has been used as a mode of treatment for major depression. Others have shown that treatment with tricyclic antidepressants also results in increased levels of TH and NET mRNA in LC. Our results suggest that the antidepressant effect of REM sleep deprivation and tricyclic antidepressants may share similar molecular changes in the norepinephrine system.

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.

Mild electrical stimulation of pontine tegmentum around locus coeruleus reduces rapid eye movement sleep in rats

The norepinephrinergic neurons in the locus coeruleus (LC) cease firing during REM sleep (REMS) and increase firing during REMS deprivation. Most of the earlier studies used lesion and transection techniques which could not confirm the role of LC in REMS generation and/or its maintenance, if at all. Hence, in this study it was hypothesized that if the LC REM-off neurons must cease firing before the onset of REMS, its continuous activation should eliminate or at least reduce REMS. Electrophysiological parameters characterizing sleep-wakefulness-REMS were recorded in freely moving male albino rats. In an attempt not to allow the REM-off LC neurons to cease firing, low intensity (200 microA), low frequency (2 Hz) rectangular (300 microseconds) pulses were continuously delivered to the LC bilaterally through chronically implanted electrodes, and the effects on sleep-wakefulness-REMS were investigated. Although the stimulation did not affect sleep state of the animals, it reduced REMS significantly. The effect on REMS was similar to that of REMS deprivation. Total duration of REMS was significantly reduced during stimulation and showed a rebound increase during the post stimulation period. This reduction in REMS duration was primarily due to a significant reduction in the REMS frequency/h while the mean REMS duration/episode was not affected. Thus, the results of this study suggest that the stimulated area (LC) affects REMS, most likely by suppression of REMS generation process.

Firing of inferior colliculus neurons in response to low-frequency sound stimulation during sleep and waking

In vivo extracellular recordings of 102 units in the central nucleus of the inferior colliculus (IC), were made in chronically implanted guinea-pigs during the sleep/wake cycle. During wakefulness, the units were classified according to their response characteristics. Most neurons (63%) recorded showed changes, increasing or decreasing in the number of evoked discharges during the animal's transitions between wakefulness and slow-wave sleep. In the paradoxical sleep phase, the result was similar; changes were observed in most neurons, while only 11% of units did not shift their discharge pattern during ipsilateral sound stimulation. The post-stimulus time histogram of the overall evoked pattern of discharge showed sleep/wake dependency, i.e. changed in 35% of the units recorded during the 50 ms of sound stimulation. Fifty-five percent of auditory neurons did not show any change in the spontaneous firing rate during slow-wave sleep as compared to the previous waking period, while 22% exhibited a discharge increase and 23% decreased their firing. During paradoxical sleep, 14 out of 17 cells increased their spontaneous firing rate. The IC auditory neurons send descending connections to regions such as the dorsal pontine nuclei, known to mediate sleep processes. Thus, for constant auditory input, the firing rate or number of discharge variations are due to functional shifts in the sleeping brain. Auditory processing is present during sleep and differs from that observed during wakefulness. Differences were observed in the evoked firing number and/or spontaneous rate, as well as in the pattern of discharge. The ultimate reason for auditory unit shifts during sleep remains yet unexplained.

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.

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

Rapid eye movement sleep deprivation is known to affect central neuronal excitability and responsiveness. Because chloride-sensitive Mg-ATPase is known to affect the neuronal transmembrane potential, this study was conducted to investigate if the enzyme activity might be affected on deprivation. The flower pot method was used for 2 and 4 days of deprivation and suitable control experiments were conducted. The enzyme activity was estimated in the microsomal preparation of the whole brain as well as in different areas of the brain in rats. The results suggested that the deprivation increased the enzyme activity although the chloride-insensitive Mg-ATPase activity remained unaffected. The increase in the enzyme activity is likely to reduce the neuronal hyperpolarization. The findings fit in with existing knowledge and help in explaining earlier observations.

Effect of rapid eye movement sleep deprivation on rat brain Na-K ATPase activity

Since rapid eye movement (REM) sleep deprivation has been reported to affect the neuronal excitability in the brain, it was hypothesized that a change in the neuronal membrane-bound Na-K ATPase activity might be at least one of the factors inducing such a change. Therefore, in this study rats were deprived of REM sleep by using the platform technique and enzyme activity was estimated in the whole brain, in different regions of the brain and in microsomal preparations. Deprivation was carried out for varying periods and suitable control experiments were conducted to rule out the possibility of nonspecific effects. The observation supported our hypothesis and showed primarily that the deprivation increased the enzyme activity in the rat brain. It showed also that the pons and the medulla were the first sites to be affected by deprivation. The probable mechanism producing such a change is discussed.

Sleep and dreaming: induction and mediation of REM sleep by cholinergic mechanisms

The most important recent work on the neurobiology of sleep has focused on the precise cellular and biochemical mechanisms of rapid eye movement sleep mediation. Direct and indirect evidence implicates acetylcholine-containing neurons in the peribrachial pons as critical in the triggering and maintenance of rapid eye movement sleep. Other new studies provide support for the hypothesis that the cholinergic generator system is gated during waking by serotonergic and noradrenergic influences. A growing consensus regarding the basic neurobiology has stimulated new thinking about the brain basis of consciousness during waking and dreaming.

Short-term REM sleep deprivation increases acetylcholinesterase activity in the medulla of rats

Involvement of cholinergic ponto-medullary brainstem mechanism regulating rapid eye movement (REM) sleep is known. Recently it was found that though short term REM deprivation influenced brainstem neuronal excitability, the activity of the brainstem acetylcholinesterase was not affected until after 96 h deprivation. Therefore, it was hypothesized that short-term REM deprivation might influence acetylcholinesterase in a restricted brainstem region. Results of this study show that the enzyme activity increased only in the medulla after 24 and 48 h REM deprivation. The flower pot technique was used for depriving the experimental rats of REM sleep. Suitable control experiments were conducted to rule out the possibility of non-specific effects. Thus, the medullary cholinergic mechanism probably is more important for REM.