Search

The timing and quality of sleep-wake cycles are regulated by interacting circadian and homeostatic mechanisms. Although the suprachiasmatic nucleus (SCN) is the principal clock, circadian clocks are active across the brain and the respective sleep-regulatory roles of SCN and local clocks are unclear. To determine the specific contribution(s) of the SCN, we used virally mediated genetic complementation, expressing Cryptochrome1 (Cry1) to establish circadian molecular competence in the suprachiasmatic hypothalamus of globally clockless, arrhythmic maleCry1/Cry2-null mice. Under free-running conditions, the rest/activity behavior ofCry1/Cry2-null controls expressing EGFP (SCNCon) was arrhythmic, whereas Cry1-complemented mice (SCNCry1) had coherent circadian behavior, comparable to that of Cry1,2-competent wild types (WTs). In SCNConmice, sleep-wakefulness, assessed by electroencephalography (EEG)/electromyography (EMG), lacked circadian organization. In SCNCry1mice, however, it matched WTs, with consolidated vigilance states [wake, rapid eye movement sleep (REMS) and non-REMS (NREMS)] and rhythms in NREMS δ power and expression of REMS within total sleep (TS). Wakefulness in SCNConmice was more fragmented than in WTs, with more wake-NREMS-wake transitions. This disruption was reversed in SCNCry1mice. Following sleep deprivation (SD), all mice showed a homeostatic increase in NREMS δ power, although the SCNConmice had reduced NREMS during the inactive (light) phase of recovery. In contrast, the dynamics of homeostatic responses in the SCNCry1mice were comparable to WTs. Finally, SCNConmice exhibited poor sleep-dependent memory but this was corrected in SCNCry1mice. In clockless mice, circadian molecular competence focused solely on the SCN rescued the architecture and consolidation of sleep-wake and sleep-dependent memory, highlighting its dominant role in timing sleep.SIGNIFICANCE STATEMENTThe circadian timing system regulates sleep-wake cycles. The hypothalamic suprachiasmatic nucleus (SCN) is the principal circadian clock, but the presence of multiple local brain and peripheral clocks mean the respective roles of SCN and other clocks in regulating sleep are unclear. We therefore used virally mediated genetic complementation to restore molecular circadian functions in the suprachiasmatic hypothalamus, focusing on the SCN, in otherwise genetically clockless, arrhythmic mice. This initiated circadian activity-rest cycles, and circadian sleep-wake cycles, circadian patterning to the intensity of non-rapid eye movement sleep (NREMS) and circadian control of REMS as a proportion of total sleep (TS). Consolidation of sleep-wake established normal dynamics of sleep homeostasis and enhanced sleep-dependent memory. Thus, the suprachiasmatic hypothalamus, alone, can direct circadian regulation of sleep-wake.

The high prevalence of sleep disturbance in neurodegenerative and psychiatric conditions is often interpreted as evidence for both sleep's sensitivity to and causal involvement in brain pathology. Nevertheless, how and which aspects of sleep contribute to brain function remains largely unknown. This review provides a critical evaluation of clinical and animal literature describing sleep and circadian disturbances in two distinct conditions and animal models thereof: Alzheimer's disease (AD) and schizophrenia. Its goal is to identify commonalities and distinctiveness of specific aspects of sleep disturbance and their relationship to symptoms across conditions. Despite limited standardisation, data imply that reductions in sleep continuity and alterations in sleep timing are common to AD and schizophrenia, whereas reductions in REM sleep and sleep spindle activity appear more specific to AD and schizophrenia, respectively. Putative mechanisms underlying these alterations are discussed. A standardised neuroscience based quantification of sleep and disease-independent assessment of symptoms in patients and animal models holds promise for furthering the understanding of mechanistic links between sleep and brain function in health and disease.

The timing and quality of sleep-wake cycles are regulated by interacting circadian and homeostatic mechanisms. Although the suprachiasmatic nucleus (SCN) is the principal circadian clock, local clocks are active across the brain and the respective sleep-regulatory roles of SCN and extra-SCN clocks are unclear. To determine the specific contribution(s) of the SCN, we used virally mediated genetic complementation, expressing Cryptochrome1 (Cry1) to restore circadian molecular competence to the SCN of globally clockless Cry1/Cry2-null mice. Under free-running conditions, the rest/activity behaviour of Cry1/Cry2-null controls which received EGFP (SCNCon) was arrhythmic, whereas Cry1-complemented mice (SCNCry1) had circadian behaviour comparable to that of Cry1,2-competent wild-types (WT). In SCNCon mice, sleep-wakefulness, assessed by electroencephalography/electromyography, also lacked circadian organisation. In SCNCry1 mice, however, it was comparable to WT, with consolidated vigilance states (wake, REM and NREM sleep) and rhythms in NREMS delta power and expression of REMS within total sleep. Wakefulness in SCNCon mice was more fragmented than in WT, with more wake-NREMS-wake transitions. This disruption was corrected in SCNCry1 mice. Following sleep deprivation, all mice showed an initial homeostatic increase in NREMS delta power. The SCNCon mice, however, had reduced, non-consolidated NREMS during the inactive phase of the recovery period. In contrast, the dynamics of homeostatic responses in the SCNCry1 mice were equivalent to WT. Finally, SCNCon mice exhibited poor sleep-dependent memory but this was corrected in SCNCry1mice. Therefore, the SCN clock is sufficient for circadian control of sleep-wake, facilitating initiation and maintenance of wake, promoting sleep consolidation, homeostatic dynamics, and sleep-dependent memory.Significance statementThe circadian timing system regulates sleep-wake cycles. The hypothalamic suprachiasmatic nucleus (SCN) is the principal circadian clock, but local clocks are also active across the brain and the respective roles of SCN and local clocks in regulating sleep are unclear. To determine, explicitly, the contribution of the SCN, we used virally mediated genetic complementation to restore SCN molecular circadian functions in otherwise genetically clockless mice. This initiated circadian activity-rest cycles, accompanied by circadian sleep-wake cycles, circadian patterning to the intensity of NREM sleep and circadian control of REM sleep as a proportion of total sleep. Consolidation of sleep-wake established normal dynamics of sleep homeostasis and enhanced sleep-dependent memory. Thus, the SCN is the principal and sufficient circadian regulator of sleep-wake.

Study Objectives Sleep restriction (SR) leads to performance decrements across cognitive domains but underlying mechanisms remain largely unknown. The impact of SR on performance in rodents is often assessed using tasks in which food is the reward. Investigating how the drives of hunger and sleep interact to modulate performance may provide insights into mechanisms underlying sleep loss-related performance decrements. Methods Three experiments were conducted in male adult Wistar rats to assess: (1) effects of food restriction on performance in the simple response latency task (SRLT) across the diurnal cycle (n = 30); (2) interaction of food restriction and SR (11 h) on SRLT performance, sleep electroencephalogram, and event-related potentials (ERP) (n = 10–13); and (3) effects of food restriction and SR on progressive ratio (PR) task performance to probe the reward value of food reinforcement (n = 19). Results Food restriction increased premature responding on the SRLT at the end of the light period of the diurnal cycle. SR led to marked impairments in SRLT performance in the ad libitum-fed group, which were absent in the food-restricted group. After SR, food-restricted rats displayed a higher amplitude of cue-evoked ERP components during the SRLT compared with the ad libitum group. SR did not affect PR performance, while food restriction improved performance. Conclusions Hunger may induce a functional resilience to negative effects of sleep loss during subsequent task performance, possibly by maintaining attention to food-related cues.

Significance Sleep disturbances are common in stress-related disorders but the nature of these sleep disturbances and how they relate to changes in the stress hormone corticosterone and changes in gene expression remained unknown. Here we demonstrate that in response to chronic mild stress, rapid–eye-movement sleep (REMS), a sleep state involved in emotion regulation and fear conditioning, changed first and more so than any other measured sleep characteristic. Transcriptomic profiles related to REMS continuity and theta oscillations overlapped with those for corticosterone, as well as with predictors for anhedonia, and were enriched for apoptotic pathways. These data highlight the central role of REMS in response to stress and warrant further investigation into REMS’s involvement in stress-related mental health disorders., One of sleep’s putative functions is mediation of adaptation to waking experiences. Chronic stress is a common waking experience; however, which specific aspect of sleep is most responsive, and how sleep changes relate to behavioral disturbances and molecular correlates remain unknown. We quantified sleep, physical, endocrine, and behavioral variables, as well as the brain and blood transcriptome in mice exposed to 9 weeks of unpredictable chronic mild stress (UCMS). Comparing 46 phenotypic variables revealed that rapid–eye-movement sleep (REMS), corticosterone regulation, and coat state were most responsive to UCMS. REMS theta oscillations were enhanced, whereas delta oscillations in non-REMS were unaffected. Transcripts affected by UCMS in the prefrontal cortex, hippocampus, hypothalamus, and blood were associated with inflammatory and immune responses. A machine-learning approach controlling for unspecific UCMS effects identified transcriptomic predictor sets for REMS parameters that were enriched in 193 pathways, including some involved in stem cells, immune response, and apoptosis and survival. Only three pathways were enriched in predictor sets for non-REMS. Transcriptomic predictor sets for variation in REMS continuity and theta activity shared many pathways with corticosterone regulation, in particular pathways implicated in apoptosis and survival, including mitochondrial apoptotic machinery. Predictor sets for REMS and anhedonia shared pathways involved in oxidative stress, cell proliferation, and apoptosis. These data identify REMS as a core and early element of the response to chronic stress, and identify apoptosis and survival pathways as a putative mechanism by which REMS may mediate the response to stressful waking experiences.

One of sleep’s putative functions is mediation of adaptation to waking experiences. Chronic stress is a common waking experience, however, which specific aspect of sleep is most responsive, and how sleep changes relate to behavioral disturbances and molecular correlates remain unknown. We quantified sleep, physical, endocrine and behavioral variables and the brain and blood transcriptome in mice exposed to nine weeks of unpredictable chronic mild stress (UCMS). Comparing 46 phenotypical variables revealed that rapid-eye-movement sleep (REMS), corticosterone regulation and coat state were most responsive to UCMS. REMS theta oscillations were enhanced whereas delta oscillations in non-REMS were unaffected. Transcripts affected by UCMS in the prefrontal cortex, hippocampus, hypothalamus and blood were associated with inflammatory and immune responses. A machine learning approach controlling for unspecific UCMS effects identified transcriptomic predictors for specific phenotypes and their overlap. Transcriptomic predictor sets for the inter-individual variation in REMS continuity and theta activity shared many pathways with corticosterone regulation and in particular pathways implicated in apoptosis, including mitochondrial pathways. Predictor sets for REMS and anhedonia, one of the behavioral changes following UCMS, shared pathways involved in oxidative stress, cell proliferation and apoptosis. RNA predictor sets for non-NREMS parameters showed no overlap with other phenotypes. These novel data identify REMS as a core and early element of the response to chronic stress, and identify apoptotic pathways as a putative mechanism by which REMS mediates adaptation to stressful waking experiences.Significance StatementSleep is responsive to experiences during wakefulness and is altered in stress-related disorders. Whether sleep changes primarily concern rapid-eye-movement sleep (REMS) or non-REM sleep, and how they correlate with stress hormones, behavioral and transcriptomic responses remained unknown. We demonstrate using unpredictable chronic (9-weeks) mild stress that REMS is the most responsive of all the measured sleep characteristics, and correlates with deficiency in corticosterone regulation. An unbiased machine learning, controlling for unspecific effects of stress, revealed that REMS correlated with RNA predictor sets enriched in apoptosis including mitochondrial pathways. Several pathways were shared with predictors of corticosterone and behavioral responses. This unbiased approach point to apoptosis as a molecular mechanism by which REMS mediates adaptation to an ecologically relevant waking experience.

Addiction to psychostimulants is a major public health problem with no available treatment. Adenosine A2A receptors (A2A R) co-localize with metabotropic glutamate 5 receptors (mGlu5 R) in the striatum and functionally interact to modulate behaviours induced by addictive substances, such as alcohol. Using genetic and pharmacological antagonism of A2A R in mice, we investigated whether A2A R-mGlu5 R interaction can regulate the locomotor, stereotypic and drug-seeking effect of methamphetamine and cocaine, two drugs that exhibit distinct mechanism of action. Genetic deletion of A2A R, as well as combined administration of sub-threshold doses of the selective A2A R antagonist (SCH 58261, 0.01 mg/kg, i.p.) with the mGlu5 R antagonist, 3-((2-methyl-4-thiazolyl)ethynyl)pyridine (0.01 mg/kg, i.p.), prevented methamphetamine- but not cocaine-induced hyperactivity and stereotypic rearing behaviour. This drug combination also prevented methamphetamine-rewarding effects in a conditioned-place preference paradigm. Moreover, mGlu5 R binding was reduced in the nucleus accumbens core of A2A R knockout (KO) mice supporting an interaction between these receptors in a brain region crucial in mediating addiction processes. Chronic methamphetamine, but not cocaine administration, resulted in a significant increase in striatal mGlu5 R binding in wild-type mice, which was absent in the A2A R KO mice. These data are in support of a critical role of striatal A2A R-mGlu5 R functional interaction in mediating the ambulatory, stereotypic and reinforcing effects of methamphetamine but not cocaine-induced hyperlocomotion or stereotypy. The present study highlights a distinct and selective mechanistic role for this receptor interaction in regulating methamphetamine-induced behaviours and suggests that combined antagonism of A2A R and mGlu5 R may represent a novel therapy for methamphetamine addiction.

Given the role that sleep plays in modulating plasticity, we hypothesized that increasing sleep would restore memory to canonical memory mutants without specifically rescuing the causal molecular-lesion. Sleep was increased using three independent strategies: activating the dorsal Fan Shaped Body (FB), increasing the expression of Fatty acid binding protein (dFabp) or by administering the GABA-A agonist 4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridine-3-ol (THIP). Short-term memory (STM) or Long-term memory (LTM) was evaluated in rutabaga (rut) and dunce (dnc) mutants using Aversive Phototaxic Suppression (APS) and courtship conditioning. Each of the three independent strategies increased sleep and restored memory to rut and dnc mutants. Importantly, inducing sleep also reverses memory defects in a Drosophila model of Alzheimer’s disease. Together these data demonstrate that sleep plays a more fundamental role in modulating behavioral plasticity than previously appreciated and suggests that increasing sleep may benefit patients with certain neurological disorders.

There is mounting evidence that the neuropeptide oxytocin is a possible candidate for the treatment of drug addiction. Oxytocin was shown to reduce methamphetamine self-administration, conditioned place-preference, hyperactivity and reinstatement in rodents, highlighting its potential for the management of methamphetamine addiction. Thus, we hypothesised that the central endogenous oxytocinergic system is dysregulated following chronic methamphetamine administration. We tested this hypothesis by examining the effect of chronic methamphetamine administration on oxytocin receptor density in mice brains with the use of quantitative receptor autoradiographic binding. Saline (4 ml/kg/day, i.p.) or methamphetamine (1 mg/kg/day, i.p.) was administered daily for 10 days to male, CD1 mice. Quantitative autoradiographic mapping of oxytocin receptors was carried out with the use of [I]-vasotocin in brain sections of these animals. Chronic methamphetamine administration induced a region specific upregulation of oxytocin receptor density in the amygdala and hypothalamus, but not in the nucleus accumbens and caudate putamen. As there is evidence suggesting an involvement of central adenosine A receptors on central endogenous oxytocinergic function, we investigated whether these methamphetamine-induced oxytocinergic neuroadaptations are mediated via an A receptor-dependent mechanism. To test this hypothesis, autoradiographic oxytocin receptor binding was carried out in brain sections of male CD1 mice lacking A receptors which were chronically treated with methamphetamine (1 mg/kg/day, i.p. for 10 days) or saline. Similar to wild-type animals, chronic methamphetamine administration induced a region-specific upregulation of oxytocin receptor binding in the amygdala and hypothalamus of A receptor knockout mice and no genotype effect was observed. These results indicate that chronic methamphetamine use can induce profound neuroadaptations of the oxytocinergic receptor system in brain regions associated with stress, emotionality and social bonding and that these neuroadaptations are independent on the presence of A receptors. These results may at least partly explain some of the behavioural consequences of chronic methamphetamine use. © 2013 Elsevier Inc. All rights reserved.

In humans, a primate-specific variable-number tandem-repeat (VNTR) polymorphism (4 or 5 repeats 54 nt in length) in the circadian gene PER3 is associated with differences in sleep timing and homeostatic responses to sleep loss. We investigated the effects of this polymorphism on circadian rhythmicity and sleep homeostasis by introducing the polymorphism into mice and assessing circadian and sleep parameters at baseline and during and after 12 h of sleep deprivation (SD). Microarray analysis was used to measure hypothalamic and cortical gene expression. Circadian behavior and sleep were normal at baseline. The response to SD of 2 electrophysiological markers of sleep homeostasis, electroencephalography (EEG) θ power during wakefulness and δ power during sleep, were greater in the Per3(5/5) mice. During recovery, the Per3(5/5) mice fully compensated for the SD-induced deficit in δ power, but the Per3(4/4) and wild-type mice did not. Sleep homeostasis-related transcripts (e.g., Homer1, Ptgs2, and Kcna2) were differentially expressed between the humanized mice, but circadian clock genes were not. These data are in accordance with the hypothesis derived from human data that the PER3 VNTR polymorphism modifies the sleep homeostatic response without significantly influencing circadian parameters.-Hasan, S., van der Veen, D. R., Winsky-Sommerer, R., Hogben, A., Laing, E. E., Koentgen, F., Dijk, D.-J., Archer, S. N. A human sleep homeostasis phenotype in mice expressing a primate-specific PER3 variable-number tandem-repeat coding-region polymorphism.

We tested the hypothesis that the effects of GABAergic agonists on behavior and the electroencephalogram (EEG) result from an increased regional synchronization in cortical circuits. The relationship between regional EEG topography, EEG synchronization and alteration of behavior was investigated by administering male C57BL/6 mice (n=7) a high, 3 mg/kg i.p. dose of muscimol, a selective GABA(A) agonist. Parietal and frontal cortical EEG, electromyogram, infrared and running wheel activity were recorded for 3 h before and 9 h after injection. Muscimol consistently elicited biphasic behavioral changes. Initially, it induced a catalepsy-like state lasting 96.0+/-12.4 min. This state was followed by a hyperactivity period of 49.7+/-5.4 min, during which the mice engaged in vigorous wheel running. During catalepsy, the EEG exhibited high amplitude waves which showed a consistent phase relationship between the frontal and parietal derivation. Moreover, the typical regional differences between the EEG spectra of the two derivations were abolished, and a redistribution of EEG power toward lower frequencies (

Sleep homeostasis and circadian rhythmicity interact to determine the timing of behavioral activity. Circadian clock genes contribute to circadian rhythmicity centrally and in the periphery, but some also have roles within sleep regulation. The clock gene Period3 ( Per3) has a redundant function within the circadian system and is associated with sleep homeostasis in humans. This study investigated the role of PER3 in sleep/wake activity and sleep homeostasis in mice by recording wheel-running activity under baseline conditions in wild-type (WT; n = 54) and in PER3-deficient ( Per3−/−; n = 53) mice, as well as EEG-assessed sleep before and after 6 h of sleep deprivation in WT ( n = 7) and Per3−/− ( n = 8) mice. Whereas total activity and vigilance states did not differ between the genotypes, the temporal distribution of wheel-running activity, vigilance states, and EEG delta activity was affected by genotype. In Per3−/− mice, running wheel activity was increased, and REM sleep and NREM sleep were reduced in the middle of the dark phase, and delta activity was enhanced at the end of the dark phase. At the beginning of the baseline light period, there was less wakefulness and more REM and NREM sleep in Per3−/− mice. Per3−/− mice spent less time in wakefulness and more time in NREM sleep in the light period immediately after sleep deprivation, and REM sleep accumulated more slowly during the recovery dark phase. These data confirm a role for PER3 in sleep-wake timing and sleep homeostasis.

Most sedative-hypnotics used in insomnia treatment target the gamma-aminobutyric acid (GABA)(A) receptors. A vast repertoire of GABA(A) receptor subtypes has been identified and displays specific electrophysiological and functional properties. GABA(A)-mediated inhibition traditionally refers to 'phasic' inhibition, arising from synaptic GABA(A) receptors which transiently inhibit neurons. However, there is growing evidence that peri- or extra-synaptic GABA(A) receptors are continuously activated by low GABA concentrations and mediate a 'tonic' conductance. This slower type of signaling appears to play a key role in controlling cell excitability. This review aims at summarizing recent knowledge on GABA transmission, including the emergence of tonic conductance, and highlighting the importance of GABA(A) receptor heterogeneity. The mechanism of action of sedative-hypnotic drugs and their effects on sleep and the electroencephalogram will be reported. Furthermore, studies using genetically engineered mice will be emphasized, providing insights into the role of GABA(A) receptors in mechanisms underlying physiological and pharmacological sleep. Finally, we will address the potential of GABA(A) receptor pharmacology for the treatment of insomnia.

While several methods have been used to restrict the sleep of experimental animals, it is often unclear whether these different forms of sleep restriction have comparable effects on sleep-wake architecture or functional capacity. The present study compared four models of sleep restriction, using enforced wakefulness by rotation of cylindrical home cages over 11 h in male Wistar rats. These included an electroencephalographic-driven 'Biofeedback' method and three non-invasive methods where rotation was triggered according to a 'Constant', 'Decreasing' or random protocol based upon the 'Weibull' distribution fit to an archival Biofeedback dataset. Sleep-wake architecture was determined using polysomnography, and functional capacity was assessed immediately post-restriction with a simple response latency task, as a potential homologue of the human psychomotor vigilance task. All sleep restriction protocols resulted in sleep loss, behavioural task disengagement and rebound sleep, although no model was as effective as real-time electroencephalographic-Biofeedback. Decreasing and Weibull protocols produced greater recovery sleep than the Constant protocol, mirrored by comparably poorer simple response latency task performance. Increases in urinary corticosterone levels following Constant and Decreasing protocols suggested that stress levels may differ between protocols. Overall, these results provide insight into the value of choosing a specific sleep restriction protocol, not only from the perspective of animal welfare and the use of less invasive procedures, but also translational validity. A more considered choice of the physiological and functional effects of sleep-restriction protocols in rodents may improve correspondence with specific types of excessive daytime sleepiness in humans.

THIP (4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridine-3-ol, Gaboxadol) is a selective c-aminobutyric acid (GABA)A agonist, acting in vitro with high potency and efficacy at the extrasynaptic GABAA d-containing receptors. THIP was suggested to be a potential hypnotic to treat insomnia, and it is currently in clinical trial. Here we assessed whether the GABAA d-containing receptors mediate in vivo the effect of THIP on sleep and the sleep electroencephalogram (EEG). We performed EEG recordings in a mouse model deficient in the GABAA d-subunit gene (d – ⁄ – mice) and in wild-type littermate controls. THIP (4 and 6 mg ⁄ kg intraperitoneally) induced an abnormal EEG pattern, resulting in dramatic changes in the waking and non-rapid eye movement (NREM) sleep EEG spectra in wild-type mice. Indeed, a massive increase in EEG power lasting 2–3 h occurred in both the frontal and parietal derivation, especially in frequencies below 6 Hz. All effects were more prominent in the frontal EEG. Furthermore, the highest dose of THIP lengthened REM sleep latency and suppressed REM sleep. In contrast, vigilance states and sleep latencies were not affected in d – ⁄ – mice. Moreover, only minor changes were observed in the NREM sleep EEG spectrum after THIP injection in the d-subunit-deficient mice. The present findings do not indicate a sleep-promoting effect of THIP in mice, which is in accordance with a previous report in this species. Moreover, our results in vivo demonstrate that THIP acts preferentially at GABAA receptors containing the d-subunit.

Nicotine addiction is considered to be the main preventable cause of death worldwide. While growing evidence indicates that the neurohypophysial peptide oxytocin can modulate the addictive properties of several abused drugs, the regulation of the oxytocinergic system following nicotine administration has so far received little attention. Here, we examined the effects of long-term nicotine or saline administration on the central oxytocinergic system using [125I]OVTA autoradiographic binding in mouse brain. Male, 7-week old C57BL6J mice were treated with either nicotine (7.8mg/kg daily; rate of 0.5μl per hour) or saline for a period of 14-days via osmotic minipumps. Chronic nicotine administration induced a marked region-specific upregulation of the oxytocin receptor binding in the amygdala, a brain region involved in stress and emotional regulation. These results provide direct evidence for nicotine-induced neuroadaptations in the oxytocinergic system, which may be involved in the modulation of nicotine-seeking as well as emotional consequence of chronic drug use.

Many studies in animals and humans suggest that sleep facilitates learning, memory consolidation, and retrieval. Moreover, sleep deprivation (SD) incurred after learning, impaired memory in humans, mice, rats, and hamsters. We investigated the importance of sleep and its timing in in object recognition task in OFI mice subjected to 6 h SD either immediately after the acquisition phase (0-6 SD) or 6h later (7-12 SD), and in corresponding undisturbed controls. Motor activity was continuously recorded with infrared sensors. All groups explored two familiar, previously encountered objects to it similar extent, both at the end of the acquisition phase and 24 h later during the test phase, indicating intact familiarity detection. During the test phase 0-6 SD mice failed to discriminate between the single novel and the two familiar objects. I it contrast, the 7-12 SD group and the two control groups explored the novel object significantly longer than the two familiar objects. Plasma corticosterone levels determined after SD did not differ from time-matched undisturbed controls, but were significantly below the level measured after learning alone. ACTH did not differ between the groups. Therefore, it is unlikely that stress contributed to the memory impairment. We conclude that the loss of sleep and the activities the mice engaged in during the SD, impaired recognition memory retrieval, when they Occurred immediately after acquisition. The delayed SD enabled memory consolidation during the 6 h when the mice were allowed to sleep, and had no detrimental effect on memory. Neither SD schedule impaired object familiarity processing, Suggesting that only specific cognitive abilities were sensitive to the intervention. Sleep may either actively promote memory formation, or alternatively, sleep may provide optimal conditions of non-interference for consolidation. (c) 2005 Elsevier Inc. All rights reserved.

Neuropeptide W (NPW) is an endogenous ligand for G protein-coupled receptor 7 (GPR7). There are two forms of the peptide, designated as neuropeptide W-23 (NPW23) and neuropeptide W-30 (NPW30). In the current study we found that intracerebroventricular administration of NPW23 increased c-Fos immunoreactivity (IR) in a variety of brain sites, many of which are involved in the regulation of feeding. In particular, we noted that c-Fos IR levels were increased in hypocretin-expressing neurons in the perifornical region of the lateral hypothalamus (LH). We then studied whether injection of NPW23 into the paraventricular nucleus of the hypothalamus (PVN) and the LH increased food intake over a 24-h time period. Intra-PVN injection of NPW23 at doses ranging from 0.1 to 3 nmol increased feeding for up to 4 h, and doses ranging from 0.3 to 3 nmol increased feeding for up to 24 h. In contrast, only the 3-nmol dose of NPW23 increased feeding after administration into the LH. Together, these data suggest a modulatory role for NPW in the control of food intake.

Oxidative stress is implicated in the death of dopaminergic neurons in sporadic forms of Parkinson's disease. Because oxidative stress can be modulated endogenously by uncoupling proteins (UCPs), we hypothesized that specific neuronal expression of UCP2, one member of the UCP family that is rapidly induced in the CNS following insults, could confer neuroprotection in a mouse model of Parkinson's disease. We generated transgenic mice overexpressing UCP2 in catecholaminergic neurons under the control of the tyrosine hydroxylase promoter (TH-UCP2). In these mice, dopaminergic neurons of the substantia nigra showed a twofold elevation in UCP2 expression, elevated uncoupling of their mitochondria, and a marked reduction in indicators of oxidative stress, an effect also observed in the striatum. Upon acute exposure to 1,2,3,6-methyl-phenyl-tetrahydropyridine, TH-UCP2 mice showed neuroprotection and retention of locomotor functions. Our data suggest that UCP2 may represent a drug target for slowing the progression of Parkinson's disease.

Cytosolic tyrosine kinases play a critical role both in neural development and in adult brain function and plasticity. Here we isolated a cDNA with high homology to human Ack1 and mouse Tnk2. This cDNA directs the expression of a 125-kD protein that can be autophosphorylated in tyrosines. Initially, this clone was named Pyk1 for proline-rich tyrosine kinase (Lev et al., 1995); however, since it corresponds to the mouse homolog of Ack1, here we called it Ack1/Pyk1. In this study we show that Ack1/Pyk1 mRNA and protein is highly expressed in the developing and adult brain. The highest levels of Ack1/Pyk1 expression were detected in the hippocampus, neocortex, and cerebellum. Electron microscopy studies showed that Ack1/Pyk1 protein is expressed in these regions both at dendritic spines and presynaptic axon terminals, indicating a role in synaptic function. Furthermore, we demonstrate that Ack1/Pyk1 mRNA levels are strongly upregulated by increased neural activity, produced by intraperitoneal kainate injections. During development, Ack1/Pyk1 was also expressed in the proliferative ventricular zones and in postmitotic maturing neurons. In neuronal cultures, Ack1/Pyk1 was detected in developing dendrites and axons, including dendritic tips and growth cones. Moreover, Ack1/Pyk1 colocalized with Cdc42 GTPase in neuronal cultures and coimmunoprecipitated with Cdc42 in HEK 293T cells. Altogether, our findings indicate that Ack1/Pyk1 tyrosine kinase may be involved both in adult synaptic function and plasticity and in brain development.

A somatostatin deficit occurs in the cerebral cortex of Alzheimer's disease patients without a major loss in somatostatin-containing neurons. This deficit could be related to a reduction in the rate of proteolytic processing of peptide precursors. Since the two proprotein convertases (PC)1 and PC2 are responsible for the processing of neuropeptide precursors directed to the regulated secretory pathway, we examined whether they are involved first in the proteolytic processing of prosomatostatin in mouse and human brain and secondly in somatostatin defect associated with Alzheimer's disease. By size exclusion chromatography, the cleavage of prosomatostatin to somatostatin-14 is almost totally abolished in the cortex of PC2 null mice, while the proportions of prosomatostatin and somatostatin-28 are increased. By immunohistochemistry, PC1 and PC2 were localized in many neuronal elements in human frontal and temporal cortex. The convertases levels were quantified by Western blot, as well as the protein 7B2 which is required for the production of active PC2. No significant change in PC1 levels was observed in Alzheimer's disease. In contrast, a marked decrease in the ratio of the PC2 precursor to the total enzymatic pool was observed in the frontal cortex of Alzheimer patients. This decrease coincides with an increase in the binding protein 7B2. However, the content and enzymatic activity of the PC2 mature form were similar in Alzheimer patients and controls. Therefore, the cortical somatostatin defect is not due to convertase alteration occuring during Alzheimer's disease. Further studies will be needed to assess the mechanisms involved in somatostatin deficiency in Alzheimer's disease.

The expression of the five somatostatin receptor subtypes, sst 1 - 5 was compared on tissue containing glial tumours (glioblastomas or oligodendrogliomas), medulloblastomas, and on normal human cortex. By semiquantitativereverse transcription coupled to polymerase chain reaction, the receptor expression profiles were high in cortex and in tissue containing oligodendrogliomas. It was moderate in medulloblastomas. Tissue containing glioblastomas displayed lower expression of somatostatin receptor subtypes, sst 1 and sst 3 being mostly expressed. By 1 2 5 I-Tyr 0 DTrp 8 somatostatin-14 or 1 2 5 I-Leu 8 DTrp 2 2 Tyr 2 5 somatostatin-28 autoradiography combined with synaptophysin immunohistochemistry, it was possible to differentiate between isolated tumoral cell component infiltrating the cerebral parenchyma (cortex or white matter) and tumoral tissue (without residual parenchyma) in glioblastomas or oligodendrogliomas. Glial tumoral tissue per se presented few somatostatin receptors. By contrast, medulloblastoma tumoral cells exhibited numerous octreotide sensitive somatostatin receptors, sst 2 immunocytochemistry demonstrated immunostaining of neuronal cells and neuropile; sst 2 and sst 3 immunostaining was identified on glioblastoma proliferating vessels endothelial cells and on medulloblastomas tumoral cells. Faint sst 2 immunostaining among glial tumoral cells was due to microglia, while glioma cells did not significantly stain. In summary, medulloblastoma tumoral cells express sst 2 /sst 3 receptors at a high level while glioma cells do not. In gliomas, sst expression is restricted to endothelial cells on proliferating vessels (displaying both sst 2 and sst 3 receptors), including parenchyma and reactive microglia (only sst 2 ). The differential expression of sst 2 /sst 3 receptors on gliomas and medulloblastomas has implications for the therapy of these tumours.

The main challenge in treating opioid addicts is to maintain abstinence due to the affective consequences associated with withdrawal which may trigger relapse. Emerging evidence suggests a role of the neurohypophysial peptide oxytocin (OT) in the modulation of mood disorders as well as drug addiction. However, its involvement in the emotional consequences of drug abstinence remains unclear. We investigated the effect of 7-day opioid abstinence on the oxytocinergic system and assessed the effect of the OT analogue carbetocin (CBT) on the emotional consequences of opioid abstinence, as well as relapse. Male C57BL/6J mice were treated with a chronic escalating-dose morphine regimen (20-100 mg/kg/day, i.p.). Seven days withdrawal from this administration paradigm induced a decrease of hypothalamic OT levels and a concomitant increase of oxytocin receptor (OTR) binding in the lateral septum and amygdala. Although no physical withdrawal symptoms or alterations in the plasma corticosterone levels were observed after 7 days of abstinence, mice exhibited increased anxiety-like and depressive-like behaviors and impaired sociability. CBT (6.4 mg/kg, i.p.) attenuated the observed negative emotional consequences of opioid withdrawal. Furthermore, in the conditioned place preference paradigm with 10 mg/kg morphine conditioning, CBT (6.4 mg/kg, i.p.) was able to prevent the stress-induced reinstatement to morphine-seeking following extinction. Overall, our results suggest that alterations of the oxytocinergic system contribute to the mechanisms underlying anxiety, depression, and social deficits observed during opioid abstinence. This study also highlights the oxytocinergic system as a target for developing pharmacotherapy for the treatment of emotional impairment associated with abstinence and thereby prevention of relapse.

Background: A difficult problem in treating opioid addicts is the maintenance of a drug-free state because of the negative emotional symptoms associated with withdrawal, which may trigger relapse. Several lines of evidence suggest a role for the metabotropic glutamate receptor 5 in opioid addiction; however, its involvement during opioid withdrawal is not clear. Methods: Mice were treated with a 7-day escalating-dose morphine administration paradigm. Following withdrawal, the development of affective behaviors was assessed using the 3-chambered box, open-field, elevated plus-maze and forced-swim tests. Metabotropic glutamate receptor 5 autoradiographic binding was performed in mouse brains undergoing chronic morphine treatment and 7 days withdrawal. Moreover, since there is evidence showing direct effects of opioid drugs on the metabotropic glutamate receptor 5 system, the presence of an metabotropic glutamate receptor 5/μ-opioid receptor interaction was assessed by performing metabotropic glutamate receptor 5 autoradiographic binding in brains of mice lacking the μ-opioid receptor gene. Results: Withdrawal from chronic morphine administration induced anxiety-like, depressive-like, and impaired sociability behaviors concomitant with a marked upregulation of metabotropic glutamate receptor 5 binding. Administration of the metabotropic glutamate receptor 5 antagonist, 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine, reversed morphine abstinence-induced depressive-like behaviors. A brain region-specific increase in metabotropic glutamate receptor 5 binding was observed in the nucleus accumbens shell, thalamus, hypothalamus, and amygdala of μ-opioid receptor knockout mice compared with controls. Conclusions: These results suggest an association between metabotropic glutamate receptor 5 alterations and the emergence of opioid withdrawal-related affective behaviors. This study supports metabotropic glutamate receptor 5 system as a target for the development of pharmacotherapies for the treatment of opioid addiction. Moreover, our data show direct effects of μ-opioid receptor system manipulation on metabotropic glutamate receptor 5 binding in the brain.

Orexins have a role in sleep regulation, and orexin receptor antagonists are under development for the treatment of insomnia. We conducted a randomised, double-blind, placebo-controlled, four-period crossover study to investigate the effect of single doses of the dual orexin receptor antagonist SB-649868 (10 or 30 mg) and a positive control zolpidem (10 mg), an allosteric modulator of GABA(A) receptors. Objective and subjective sleep parameters and next-day performance were assessed in 51 healthy male volunteers in a traffic noise model of situational insomnia. Compared with placebo, SB-649868 10 and 30 mg increased total sleep time (TST) by 17 and 31 min (p

Sleep and sleep intensity are enhanced by adenosine and its receptor agonists, whereas adenosine receptor antagonists induce wakefulness. Adenosine kinase (ADK) is the primary enzyme metabolizing adenosine in adult brain. To investigate whether adenosine metabolism or clearance affects sleep, we recorded sleep in mice with engineered mutations inAdk. Adk-tg mice overexpress a transgene encoding the cytoplasmic isoform of ADK in the brain but lack the nuclear isoform of the enzyme. Wild-type mice andAdk+/−mice that have a 50% reduction of the cytoplasmic and the nuclear isoforms of ADK served as controls.Adk-tg mice showed a remarkable reduction of EEG power in low frequencies in all vigilance states and in theta activity (6.25–11 Hz) in rapid eye movement (REM) sleep and waking.Adk-tg mice were awake 58 min more per day than wild-type mice and spent significantly less time in REM sleep (102 ± 3 vs 128 ± 3 min in wild type). After sleep deprivation, slow-wave activity (0.75–4 Hz), the intensity component of non-rapid eye movement sleep, increased significantly less inAdk-tg mice and their slow-wave energy was reduced. In contrast, the vigilance states and EEG spectra ofAdk+/−and wild-type mice did not differ. Our data suggest that overexpression of the cytoplasmic isoform of ADK is sufficient to alter sleep physiology. ADK might orchestrate neurotransmitter pathways involved in the generation of EEG oscillations and regulation of sleep.

Thalamo-cortical networks generate specific patterns of oscillations during distinct vigilance states and epilepsy, well characterized by electroencephalography (EEG). Oscillations depend on recurrent synaptic loops, which are controlled by GABAergic transmission. In particular, GABA A receptors containing the alpha3 subunit are expressed predominantly in cortical layer VI and thalamic reticular nucleus (nRT) and regulate the activity and firing pattern of neurons in relay nuclei. Therefore, ablation of these receptors by gene targeting might profoundly affect thalamo-cortical oscillations. Here, we investigated the role of alpha3-GABA A receptors in regulating vigilance states and seizure activity by analyzing chronic EEG recordings in alpha3 subunit-knockout (alpha3-KO) mice. The presence of postsynaptic alpha3-GABA A receptors/gephyrin clusters in the nRT and GABA A-mediated synaptic currents in acute thalamic slices was also examined. EEG spectral analysis showed no difference between genotypes during non rapid-eye movement (NREM) sleep or at waking-NREM sleep transitions. EEG power in the spindle frequency range (10-15 Hz) was significantly lower at NREM-REM sleep transitions in mutant compared with wild-type mice. Enhancement of sleep pressure by 6 h sleep deprivation did not reveal any differences in the regulation of EEG activities between genotypes. Finally, the waking EEG showed a slightly larger power in the 11-13-Hz band in alpha3-KO mice. However, neither behavior nor the waking EEG showed alterations suggestive of absence seizures. Furthermore, alpha3-KO mice did not differ in seizure susceptibility in a model of temporal lobe epilepsy. Strikingly, despite the disruption of postsynaptic gephyrin clusters, whole-cell patch clamp recordings revealed intact inhibitory synaptic transmission in the nRT of alpha3-KO mice. These findings show that the lack of alpha3-GABA(A) receptors is extensively compensated for to preserve the integrity of thalamo-cortical function in physiological and pathophysiological situations.

Reduction of core body temperature has been proposed to contribute to the increased life span and the antiaging effects conferred by calorie restriction (CR). Validation of this hypothesis has been difficult in homeotherms, primarily due to a lack of experimental models. We report that transgenic mice engineered to overexpress the uncoupling protein 2 in hypocretin neurons (Hcrt-UCP2) have elevated hypothalamic temperature. The effects of local temperature elevation on the central thermostat resulted in a 0.3° to 0.5°C reduction of the core body temperature. Fed ad libitum, Hcrt-UCP2 transgenic mice had the same caloric intake as their wild-type littermates but had increased energy efficiency and a greater median life span (12% increase in males; 20% increase in females). Thus, modest, sustained reduction of core body temperature prolonged life span independent of altered diet or CR.

This chapter focuses on brain somatostatin-related peptides. Somatostatin-14 was originally characterized as a hypothalamic neurohormone responsible for the inhibition of pituitary growth hormone secretion. In the mammalian brain, two genes encode for the prosomatostatin-derived peptides, somatostatin-14 and -28, and procortistatin-related ones, respectively. Somatotropin release inhibiting factor (SRIF) immunoreactivity is largely distributed in many neurons in mammalian brain, including the human brain. The highest levels are found in the mediobasal hypothalamus and median eminence, amygdala, preoptic area, accumbens nucleus, cerebral cortex, striatum olfactory regions, and brain stem. SRIF mediates its biological functions via at least six receptor subtypes, termed sstl, sst2A, sst2B, sst3, sst4, and sst5, which all belong to the family of seven transmembrane domain G-protein-coupled receptors. With the noticeable exception of sst4, all subtypes do internalize in various cellular models following agonist treatment. In the brain, this has only been shown in vivo for the sst2 receptor. Although the sst2 receptor is the candidate likely to mediate the anticonvulsant effects of SRIF in the rat hippocampus, in the mouse hippocampus recent observations support a central role of sst4 and/or sst1 receptors in mediating SRIF inhibition of epileptiform activity. © 2006 Elsevier Inc. All rights reserved.

We measured preprocortistatin mRNA expression in young and aged transgenic (Tg) mice overexpressing the human beta-amyloid precursor protein (hbetaAPP) under the platelet-derived growth factor-beta promoter. Our findings suggest that the significant increase in hippocampal cortistatin mRNA expression during normal aging is significantly attenuated in Tg mice at an age known to exhibit beta-amyloid protein (Abeta) deposition. These deficits in cortistatin expression may play a role in the deficits in hippocampal-dependent spatial learning and sleep/wake states previously demonstrated in aged Tg mice.

Light bulbs, television, computers and shift work have all altered sleeping habits. This has huge implications for sleep deprivation and our health

We measured somatostatin-like immunoreactivity, using a radioimmunoassay which does not cross react with cortistatin-like immunoreactivity, in postmortem frontal cortex (Brodmann area 9) from 32 patients, of different apolipoprotein E genotypes, and presenting with different degrees of cognitive impairment. Eleven subjects and eight patients presented with no (controls) or limited memory impairments (Borderline), respectively. Six patients with clinical criteria for possible Alzheimer's disease also presented with clinical or brain imaging of cerebrovascular disease (mixed dementia) and seven patients were classified as Alzheimer's disease (AD). In the 6 months preceeding their deaths, all subjects had been evaluated by Folstein's Mini Mental State examination (MMS). Sixty nine percent of patients with MMS >20 did not carry the epsilon 4 allele while 66% of patients with MMS

Recent studies have led to the discovery of a neuropeptide system that regulates arousal states, The hypocretins (hcrt1 and hcrt2, also called the orexins) are neuropeptides of related sequence derived from the same precursor whose expression is restricted to a few thousand neurons of the lateral hypothalamus. Two G-protein-coupled receptors for the hypocretins have been identified, and these have different distributions within the central nervous system and differential affinities for the two hypocretins. Hypocretin fibers project throughout the brain, including several areas implicated in cardiovascular function and regulation of the sleep-wake cycle. Central administration of synthetic hypocretin-1 affects blood pressure, hormone secretion and locomotor activity, and increases wakefulness while suppressing rapid eye movement sleep. Most human patients with narcolepsy have greatly reduced levels of hypocretin peptides in their cerebral spinal fluid and no or barely detectable hypocretin neurons in their hypothalami, suggestive of autoimmune attack. Development of nonpeptidergic hypocretin antagonists may prove useful in sleep disorders, whereas hypocretin agonists may be used to treat narcolepsy and excessive daytime sleepiness. The hypocretins are also an excellent target for the pharmacological treatment of the deregulated arousal state that characterizes depression or addictive behavior. (C) 2003 Prous Science. All rights reserved.

PC1 and PC2 are two major enzymes involved in the processing of protein precursors directed to the regulated secretory pathway. Whereas transcripts encoding both enzymes are widely distributed in the central nervous system, information regarding the localization of proteins themselves is still lacking. In an attempt to gain insight into the neurobiologic roles of PC1 and PC2, both enzymes were immunolocalized in the rat brain by using C-terminally directed antibodies, which respectively recognize the 87-kDa PC1 and the 75 and 68-kDa PC2 forms. Adjacent sections immunoreacted with PC1 or PC2 antibodies exhibited selective patterns of immunostaining in regions well characterized with respect to their biosynthesis of multiple neuropeptides such as the cerebral cortex, hippocampus, and hypothalamus. PC1 signal intensity was generally weaker than that of PC2, although both enzymes displayed extensive overlapping patterns of expression. As assessed by double-labeling experiments at the cellular level, PC1 and PC2 immunoreactive signals were localized within the trans-Golgi network and nerve terminals, in keeping with the biosynthetic pathways of neuropeptides. Immunoreactive fibers were detected in many areas throughout the brain but were particularly densely distributed in the hypothalamus and the brainstem. Both enzymes were also localized within dendrites of numerous neurons, supporting the hypothesis that dendritic neuropeptide maturation and release may occur in a large number of brain regions. Taken together, our results provide new evidence that both convertases are efficiently targeted to the neuronal regulated secretory pathway and are well poised to process protein precursors in biologically active end-products within the mammalian brain. J. Comp. Neurol. 424:439–460, 2000. © 2000 Wiley-Liss, Inc.