Regulation Of Paradoxical Sleep Research Articles

Genetic inactivation of glutamate neurons in the rat sublaterodorsal tegmental nucleus recapitulates REM sleep behaviour disorder.

SEE SCHENCK AND MAHOWALD DOI101093/AWW329 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Idiopathic REM sleep behaviour disorder is characterized by the enactment of violent dreams during paradoxical (REM) sleep in the absence of normal muscle atonia. Accumulating clinical and experimental data suggest that REM sleep behaviour disorder might be due to the neurodegeneration of glutamate neurons involved in paradoxical sleep and located within the pontine sublaterodorsal tegmental nucleus. The purpose of the present work was thus to functionally determine first, the role of glutamate sublaterodorsal tegmental nucleus neurons in paradoxical sleep and second, whether their genetic inactivation is sufficient for recapitulating REM sleep behaviour disorder in rats. For this goal, we first injected two retrograde tracers in the intralaminar thalamus and ventral medulla to disentangle neuronal circuits in which sublaterodorsal tegmental nucleus is involved; second we infused bilaterally in sublaterodorsal tegmental nucleus adeno-associated viruses carrying short hairpin RNAs targeting Slc17a6 mRNA [which encodes vesicular glutamate transporter 2 (vGluT2)] to chronically impair glutamate synaptic transmission in sublaterodorsal tegmental nucleus neurons. At the neuroanatomical level, sublaterodorsal tegmental nucleus neurons specifically activated during paradoxical sleep hypersomnia send descending efferents to glycine/GABA neurons within the ventral medulla, but not ascending projections to the intralaminar thalamus. These data suggest a crucial role of sublaterodorsal tegmental nucleus neurons rather in muscle atonia than in paradoxical sleep generation. In line with this hypothesis, 30 days after adeno-associated virus injections into sublaterodorsal tegmental nucleus rats display a decrease of 30% of paradoxical sleep daily quantities, and a significant increase of muscle tone during paradoxical sleep concomitant to a tremendous increase of abnormal motor dream-enacting behaviours. These animals display symptoms and behaviours during paradoxical sleep that closely mimic human REM sleep behaviour disorder. Altogether, our data demonstrate that glutamate sublaterodorsal tegmental nucleus neurons generate muscle atonia during paradoxical sleep likely through descending projections to glycine/GABA premotor neurons in the ventral medulla. Although playing a role in paradoxical sleep regulation, they are, however, not necessary for inducing the state itself. The present work further validates a potent new preclinical REM sleep behaviour disorder model that opens avenues for studying and treating this disabling sleep disorder, and advances potential regions implicated in prodromal stages of synucleinopathies such as Parkinson's disease.

Sleep in prenatally restraint stressed rats, a model of mixed anxiety-depressive disorder.

Prenatal restraint stress (PRS) can induce persisting changes in individual's development. PRS increases anxiety and depression-like behaviors and induces changes in the hypothalamo-pituitary-adrenal (HPA) axis in adult PRS rats after exposure to stress. Since adaptive capabilities also depend on temporal organization and synchronization with the external environment, we studied the effects of PRS on circadian rhythms, including the sleep-wake cycle, that are parameters altered in depression. Using a restraint stress during gestation, we showed that PRS induced phase advances in hormonal/behavioral circadian rhythms in adult rats, and an increase in the amount of paradoxical sleep, positively correlated to plasma corticosterone levels. Plasma corticosterone levels were also correlated with immobility in the forced swimming test, indicating a depressive-like profile in the PRS rats. We observed comorbidity with anxiety-like profile on PRS rats that was correlated with a reduced release of glutamate in the ventral hippocampus. Pharmacological approaches aimed at modulating glutamate release may represent a novel therapeutic strategy to treat stress-related disorders. Finally, since depressed patients exhibit changes in HPA axis activity and in circadian rhythmicity as well as in the paradoxical sleep regulation, we suggest that PRS could represent an original animal model of depression.

Differential effect of procaine injection into the rostral and caudal part of the nucleus pontis oralis on hippocampal theta rhythm in urethane-anesthetized rats.

The nucleus reticularis pontis oralis (RPO) is a reticular structure important for the regulation of paradoxical sleep (PS). However, the data concerning the relation between the RPO and the main tonic indicator of PS, hippocampal theta rhythm, are contradictory: although electrical or cholinergic stimulation of the RPO evoked well-synchronized theta activity, the electrolytic lesion of the structure had no effect on theta. In our experiment, the effect of procaine injections into different parts of the RPO on the electrical activity of the hippocampus, as well as on tail pinch-elicited hippocampal theta rhythm was assessed in urethanized rats. Power spectral analysis was performed using a Fast Fourier Transform routine in 1-Hz and 3-Hz bands between 0.6 and 12 Hz frequency. We have found that unilateral procaine inactivation of neurons in the caudal part of the RPO blocked the sensory-elicited theta rhythm. The same injection into the rostral RPO either had no effect or evoked long-lasting episodes of theta rhythm without sensory stimulation. These results suggest functional diversity of the parts of the RPO in mechanisms underlying production of hippocampal theta.

Dopaminergic neurons expressing Fos during waking and paradoxical sleep in the rat

Formerly believed to contribute to behavioural waking (W) alone, dopaminergic (DA) neurons are now also known to participate in the regulation of paradoxical sleep (PS or REM) in mammals. Indeed, stimulation of postsynaptic DA1 receptors with agonists induces a reduction in the daily amount of PS. DA neurons in the ventral tegmental area were recently shown to fire in bursts during PS, but nothing is known about the activity of the other DA cell groups in relation to waking or PS. To fulfil this gap, we used a protocol in which rats were maintained in continuous W for 3 h in a novel environment, or specifically deprived of PS for 3 days with some of them allowed to recover from this deprivation. A double immunohistochemical labeling with Fos and tyrosine hydroxylase was then performed. DA neurons in the substantia nigra (A9) and ventral tegmental area (A10), and its dorsocaudal extension in the periaqueductal gray (A10dc), almost never showed a Fos-immunoreactive nucleus, regardless of the experimental condition. The caudal hypothalamic (A11) group showed a moderate activation after PS deprivation and novel environment. During PS-recovery, the zona incerta (A13) group contained a significant number and percentage of double-labeled neurons. These results suggest that some DA neurons (A11) could participate in waking and/or the inhibition of PS during PS deprivation whereas others (A13) would be involved in the control of PS.

Role of the melanin-concentrating hormone neuropeptide in sleep regulation

Melanin-concentrating hormone (MCH), a neuropeptide secreted by a limited number of neurons within the tuberal hypothalamus, has been drawn in the field of sleep only fairly recently in 2003. Since then, growing experimental evidence indicates that MCH may play a crucial role in the homeostatic regulation of paradoxical sleep (PS). MCH-expressing neurons fire specifically during PS. When injected icv MCH induces a 200% increase in PS quantities in rats and the lack of MCH induces a decrease in sleep quantities in transgenic mice. Here, we review recent studies suggesting a role for MCH in the regulation of the sleep–wake cycle, in particular PS, including insights on (1) the specific activity of MCH neurons during PS; (2) how they might be controlled across the sleep–wake cycle; (3) how they might modulate PS; (4) and finally whether MCH might take part in the expression of some symptoms observed in primary sleep disorders.

Role of the dorsal paragigantocellular reticular nucleus in paradoxical (rapid eye movement) sleep generation: a combined electrophysiological and anatomical study in the rat

It is well known that noradrenergic locus coeruleus neurons decrease their activity during slow wave sleep and are quiescent during paradoxical sleep. It was recently proposed that their inactivation during paradoxical sleep is due to a tonic GABAergic inhibition arising from neurons located into the dorsal paragigantocellular reticular nucleus (DPGi). However, the discharge profile of DPGi neurons across the sleep–waking cycle as well as their connections with brain areas involved in paradoxical sleep regulation remain to be described. Here we show, for the first time in the unanesthetized rat that the DPGi contained a subtype of neurons with a tonic and sustained firing activation specifically during paradoxical sleep (PS-on neurons). Noteworthy, their firing rate increase anticipated for few seconds the beginning of the paradoxical sleep bout. By using anterograde tract-tracing, we further showed that the DPGi, in addition to locus coeruleus, directly projected to other areas containing wake-promoting neurons such as the serotonergic neurons of the dorsal raphe nucleus and hypocretinergic neurons of the posterior hypothalamus. Finally, the DPGi sent efferents to the ventrolateral part of the periaqueductal gray matter known to contain paradoxical sleep-suppressing neurons. Taken together, our original results suggest that the PS-on neurons of the DPGi may have their major role in simultaneous inhibitory control over the wake-promoting neurons and the permissive ventrolateral part of the periaqueductal gray matter as a means of influencing vigilance states and especially PS generation.

L0017 Additional evidence concerning the role of brain adrenergic system in the regulation of paradoxical sleep

L0017 Additional evidence concerning the role of brain adrenergic system in the regulation of paradoxical sleep

Paradoxical Sleep in Mice Lacking M3 and M2/M4 Muscarinic Receptors

Acetylcholine is crucial for the regulation of paradoxical sleep (PS) and EEG theta activity. To determine the contribution of individual muscarinic receptors to these events, we analyzed the sleep-waking cycle and EEG activities of mice lacking functional M₃ or M₂/M₄receptors. Daily PS amounts were significantly decreased in M3–/– (–22%) but not in M2/M4–/– mice. Further, the theta peak frequency for PS was significantly increased in both M2/M4–/– and M3–/– mice. This study supports the potential role of M₃ rather than M₂ and M₄ muscarinic receptors in the modulation of PS in mice and strengthens the idea that multiple muscarinic receptors contribute to the regulation of the EEG theta activity during PS.

Changes in the sleep–wake cycle architecture and cortical nitric oxide release during ageing in the rat

Changes in sleep–wake states and nitric oxide release were examined in aged rats versus young-adult ones. Sleep-wake recordings and nitric oxide measurements were taken from animals chronically equipped with polygraphic and voltametric electrodes. Animals were examined in baseline conditions and in response to a 24-hour paradoxical sleep deprivation. In aged rats, basal amount of paradoxical sleep is decreased during the light phase versus young-adult animals. After paradoxical sleep deprivation, a paradoxical sleep rebound occurs with an amount and intensity that are less marked in aged animals than in young-adult rats. The amplitude of the circadian distribution for wakefulness, slow-wave sleep and paradoxical sleep amounts is reduced with age. Finally, δ-slow-wave sleep and θ-paradoxical sleep power spectra are attenuated either in baseline conditions or after paradoxical sleep deprivation in aged animals. It is also reported that cortical nitric oxide release exhibits a circadian rhythm with higher amplitude in aged rats than in young-adult ones. However, after paradoxical sleep deprivation, a limited overproduction of nitric oxide is obtained compared with young-adult ones. These results, evidencing the dynamics of the nitric oxide changes occurring in relation to the sleep-wake cycle, point out the homeostatic paradoxical sleep regulation as an age-dependent process in which the nitric oxide molecule is possibly involved.

A role of melanin-concentrating hormone producing neurons in the central regulation of paradoxical sleep

BackgroundPeptidergic neurons containing the melanin-concentrating hormone (MCH) and the hypocretins (or orexins) are intermingled in the zona incerta, perifornical nucleus and lateral hypothalamic area. Both types of neurons have been implicated in the integrated regulation of energy homeostasis and body weight. Hypocretin neurons have also been involved in sleep-wake regulation and narcolepsy. We therefore sought to determine whether hypocretin and MCH neurons express Fos in association with enhanced paradoxical sleep (PS or REM sleep) during the rebound following PS deprivation. Next, we compared the effect of MCH and NaCl intracerebroventricular (ICV) administrations on sleep stage quantities to further determine whether MCH neurons play an active role in PS regulation.ResultsHere we show that the MCH but not the hypocretin neurons are strongly active during PS, evidenced through combined hypocretin, MCH, and Fos immunostainings in three groups of rats (PS Control, PS Deprived and PS Recovery rats). Further, we show that ICV administration of MCH induces a dose-dependant increase in PS (up to 200%) and slow wave sleep (up to 70%) quantities.ConclusionThese results indicate that MCH is a powerful hypnogenic factor. MCH neurons might play a key role in the state of PS via their widespread projections in the central nervous system.

Involvement of 5-HT1A Receptors in Homeostatic and Stress-Induced Adaptive Regulations of Paradoxical Sleep: Studies in 5-HT1A Knock-Out Mice

For the last two decades, the involvement of 5-HT(1A) receptors in the regulation of vigilance states has been studied extensively thanks to pharmacological tools, but clear-cut conclusion has not been reached yet. By studying mutant mice that do not express this receptor type (5-HT(1A)-/-) and their wild-type 129/Sv counterparts, we herein demonstrate that 5-HT(1A) receptors play key roles in the control of spontaneous sleep-wakefulness cycles, as well as in homeostatic regulation and stress-induced adaptive changes of paradoxical sleep. Both strains of mice exhibited a diurnal sleep-wakefulness rhythm, but 5-HT(1A)-/- animals expressed higher amounts of paradoxical sleep than wild-type mice during both the light and the dark phases. In wild-type mice, pharmacological blockade of 5-HT(1A) receptors by WAY 100635 (0.5 mg/kg, i.p.) promoted paradoxical sleep, whereas the 5-HT(1A) agonist 8-OH-DPAT (0.25-1 mg/kg, s.c.) had an opposite effect. In contrast, none of the 5-HT(1A) receptor ligands affected sleep significantly in 5-HT(1A)-/- mice. However, 5-HT(1B) receptor stimulation by CP 94253 (1-3 mg/kg, i.p.) induced a reduction in paradoxical sleep in both strains, this effect being more pronounced in 5-HT(1A)-/- mutants. Finally, in contrast to wild-type mice, 5-HT(1A)-/- mutants did not exhibit any rebound of paradoxical sleep after either a 9 hr instrumental paradoxical sleep deprivation or a 90 min immobilization stress. Altogether, these data indicate that, in the mouse, 5-HT(1A) receptors participate in the spontaneous and homeostatic regulation, as well as in stress-induced adaptive changes of paradoxical sleep.

Involvement of 5-HT1A receptors in homeostatic and stress-induced adaptive regulations of paradoxical sleep: studies in 5-HT1A knock-out mice.

For the last two decades, the involvement of 5-HT(1A) receptors in the regulation of vigilance states has been studied extensively thanks to pharmacological tools, but clear-cut conclusion has not been reached yet. By studying mutant mice that do not express this receptor type (5-HT(1A)-/-) and their wild-type 129/Sv counterparts, we herein demonstrate that 5-HT(1A) receptors play key roles in the control of spontaneous sleep-wakefulness cycles, as well as in homeostatic regulation and stress-induced adaptive changes of paradoxical sleep. Both strains of mice exhibited a diurnal sleep-wakefulness rhythm, but 5-HT(1A)-/- animals expressed higher amounts of paradoxical sleep than wild-type mice during both the light and the dark phases. In wild-type mice, pharmacological blockade of 5-HT(1A) receptors by WAY 100635 (0.5 mg/kg, i.p.) promoted paradoxical sleep, whereas the 5-HT(1A) agonist 8-OH-DPAT (0.25-1 mg/kg, s.c.) had an opposite effect. In contrast, none of the 5-HT(1A) receptor ligands affected sleep significantly in 5-HT(1A)-/- mice. However, 5-HT(1B) receptor stimulation by CP 94253 (1-3 mg/kg, i.p.) induced a reduction in paradoxical sleep in both strains, this effect being more pronounced in 5-HT(1A)-/- mutants. Finally, in contrast to wild-type mice, 5-HT(1A)-/- mutants did not exhibit any rebound of paradoxical sleep after either a 9 hr instrumental paradoxical sleep deprivation or a 90 min immobilization stress. Altogether, these data indicate that, in the mouse, 5-HT(1A) receptors participate in the spontaneous and homeostatic regulation, as well as in stress-induced adaptive changes of paradoxical sleep.

Key Role of 5-HT1BReceptors in the Regulation of Paradoxical Sleep as Evidenced in 5-HT1BKnock-Out Mice

The involvement of 5-HT1B receptors in the regulation of vigilance states was assessed by investigating the spontaneous sleep-waking cycles and the effects of 5-HT receptor ligands on sleep in knock-out (5-HT1B-/-) mice that do not express this receptor type. Both 5-HT1B-/- and wild-type 129/Sv mice exhibited a clear-cut diurnal sleep-wakefulness rhythm, but knock-out animals were characterized by higher amounts of paradoxical sleep and lower amounts of slow-wave sleep during the light phase and by a lack of paradoxical sleep rebound after deprivation. In wild-type mice, the 5-HT1B agonists CP 94253 (1-10 mg/kg, i.p.) and RU 24969 (0.25-2.0 mg/kg, i.p.) induced a dose-dependent reduction of paradoxical sleep during the 2-6 hr after injection, whereas the 5-HT1B/1D antagonist GR 127935 (0.1-1.0 mg/kg, i.p.) enhanced paradoxical sleep. In addition, pretreatment with GR 127935, but not with the 5-HT1A antagonist WAY 100635, prevented the effects of both 5-HT1B agonists. In contrast, none of the 5-HT1B receptor ligands, at the same doses as those used in wild-type mice, had any effect on sleep in 5-HT1B-/- mutants. Finally, the 5-HT1A agonist 8-OH-DPAT (0.2-1.2 mg/kg, s.c.) induced in both strains a reduction in the amount of paradoxical sleep. Altogether, these data indicate that 5-HT1B receptors participate in the regulation of paradoxical sleep in the mouse.

Effects of the CLIP fragment ACTH 20-24 on the duration of REM sleep episodes.

Substances acting upon rapid eye movement (REM) sleep or paradoxical sleep (PS) can affect the number and/or the duration of PS episodes. In the present study, we investigated the effects of the proopiomelanocortin-derived peptide CLIP (corticotropin-like intermediate lobe peptide, ACTH 18-39) and its N-terminal fragments ACTH 18-24 and ACTH 20-24 on the duration of PS episodes in rats. Intracerebroventricular injection of ACTH 20-24 caused a pronounced prolongation of PS episodes (up to 7 min duration, never seen under baseline conditions), whereas ACTH 18-24 acted in a similar way but without reaching statistical significance. We suggest that short N-terminal CLIP fragment(s) may represent endogenous hypnogenic factor(s) involved in the regulation of paradoxical sleep.

Effects of CLIP (corticotropin-like intermediate lobe peptide) and CLIP fragments on paradoxical sleep in rats

The effects of the POMC-derived peptide CLIP [corticotropin-like intermediate lobe peptide; ACTH(18–39)] and its shorter fragments ACTH(25–39), ACTH(18–24), and ACTH(20–24) on sleep were investigated in rats housed under normal 12-h light/12-h dark conditions (0600 light on). CLIP (10 ng) or equimolar doses of CLIP fragments, respectively, were injected intracerebroventricularly immediately before the 8-h recording period (0800–1600). It was found that paradoxical sleep (PS) was increased by CLIP (+20%) as well as by the N- terminal CLIP fragment ACTH(18–24) (+18%) and by the pentapeptide ACTH(20–24) (+25%), whereas the C- terminal fragment ACTH(25–39) was ineffective. Slow-wave sleep (SWS) was not influenced. These results clearly demonstrate that CLIP and its N- terminal fragments have selective PS-enhancing effects. CLIP and/or CLIP partial sequences are possible candidates for endogenous PS-inducing peptides involved in the physiological regulation of paradoxical sleep.

Paradoxical sleep-promoting effects of brain extract from paradoxical sleep-deprived rats

Brain extract was obtained from whole brains of donor rats following four days of paradoxical sleep deprivation (PSD). Intraperitoneal injection of this brain extract in normal (i.e., not pretreated) recipient rats led to a significant increase of paradoxical sleep (PS) which was beginning at the third hour postinjection and still present on the day after treatment. Both PS episode number and PS episode duration were increased by the PSD extract, whereas slow-wave sleep was not influenced. Brain extract of nondeprived control rats, on the other hand, had no significant effects. In the present experiments, an extract volume obtained from two donor brains was transferred to one recipient. Compared to our earlier investigations (one donor brain/one recipient) this higher “dose” of PSD extract exerted a more pronounced and prolonged effect. These results support the idea that some PS-inducing factor(s) accumulating in the brain during PS deprivation may be involved in the regulation of paradoxical sleep.

The regulation of paradoxical sleep by the hypothalamo-hypophysis.

The regulation of paradoxical sleep by the hypothalamo-hypophysis.

β1 and β2 adrenergic receptors: Their role in the regulation of paradoxical sleep in the rat

The influences of β adrenergic transmission on the regulation of paradoxical sleep (PS) were analysed in the rat. Pharmacological experiments have use β 1,2 as well as preferential β 1 or β 2 compounds. The blockade of the β 1 adrenoceptors induced a dose-related PS decrease, and stimulation of these preblocked receptors prevented this PS insomnia. SWS was generally not affected. It is concluded that β 1 neurotransmission is directly involved in the regulation of PS.

Biochemical pharmacology of paradoxical sleep.

The role of noradrenergic cells in the regulation of paradoxical sleep is still controversial, and experimental data have given rise to contradictory interpretations. Early investigations focused primarily on chemical neurotransmissions. However, the process of information transmission between cells involves many other factors, and the cell surface is an important site for transduction of messages into modifications of the activity of postsynaptic cells. alpha-adrenoceptors are believed to play an important role in the control of wakefulness and paradoxical sleep. Experimental evidence suggests that physiological modulation of receptor sensitivity, possibly by specific neuro-modulators, may be a key mechanism in synaptic transmission. In the investigation of the mechanisms involved in paradoxical sleep regulation, lesions of the locus coeruleus have given equivocal results. Collateral inhibition, probably mediated by alpha 2-adrenoceptors, appears to be a powerful mechanism. The exact temporal relationship between noradrenergic cell activation and paradoxical sleep production is not established, but 5-HT appears to be involved. Differences between paradoxical sleep and waking may be related to a physiological modulation of alpha 2-adrenoceptor sensitivity.

Regulation of sleep after neonatal locus coeruleus lesion: Functional evidence of β-adrenergic supersensitivity

In the present report we analyzed the long-term effects of neonatal noradrenergic denervation on the regulation of paradoxical sleep in the rat. The locus coeruleus was destroyed bilaterally at 4 days of age by direct infusion of 6-hydroxydopamine into the nuclei. After they reached adulthood, the rats received either i.p. injections of a β-blocker, propranolol, or the same treatment combined with intraventricular infusion of a β-agonist, isoproterenol. Several doses of each drug were tested. The effects of propranolol, alone and together with isoproterenol, on paradoxical sleep (a decrease for the former drug and a restoration for the latter combination) were significantly more pronounced in the lesioned group than in age-paired controls. These data illustrate a functional aspect of the denervation supersensitivity phenomenon in β-receptors.