The noradrenaline reuptake inhibitor atomoxetine phase-shifts the circadian clock in mice

Influence of extreme light/dark cycles on monoamine levels, physiological indices, and emotional behaviors in rats

Aberrant light/dark (LD) cycles are prevalent in modern society due to electric light usage, leading to mood disorders from circadian disruption or misalignment. However, research on the physiological and behavioral effects of LD variations on brain neurotransmitters is limited. We investigated the effects of extreme LD cycles on body weight (BW), core body temperature (Tcore), locomotor activity (ACT), emotional behaviors, and monoamine levels (noradrenaline [NA], dopamine [DA], and serotonin [5-HT]) in male Wistar rats that were exposed to 1 month of either long light phase (20 L:4D), long dark phase (4 L:20D), or normal (12 L:12D) LD cycles. The 20 L:4D rats exhibited blunted rhythms, with decreased amplitude and advanced/delayed acrophase in Tcore and ACT, alongside increased BW. The 4 L:20D rats showed circadian misalignment, with increased/decreased amplitude in Tcore or ACT and delayed acrophase in Tcore and ACT, also gaining BW. In the 20 L:4D group, NA and 5-HT levels decreased in the suprachiasmatic nucleus and amygdala, respectively, while the 4 L:20D group had increased DA and 5-HT levels in the caudate putamen and dorsomedial hypothalamus, respectively. Open field and social interaction tests indicated anxiety-like behaviors in both test groups. Overall, each extreme LD cycle affected Tcore, ACT amplitude, acrophase, and monoamine levels differently, inducing anxiogenic responses.

The circadian system: A neglected player in neurodevelopmental disorders

Patients with neurodevelopmental disorders, such as autism spectrum disorder, often display abnormal circadian rhythms. The role of the circadian system in these disorders has gained considerable attention over the last decades. Yet, it remains largely unknown how these disruptions occur and to what extent they contribute to the disorders' development. In this review, we examine circadian system dysregulation as observed in patients and animal models of neurodevelopmental disorders. Second, we explore whether circadian rhythm disruptions constitute a risk factor for neurodevelopmental disorders from studies in humans and model organisms. Lastly, we focus on the impact of psychiatric medications on circadian rhythms and the potential benefits of chronotherapy. The literature reveals that patients with neurodevelopmental disorders display altered sleep-wake cycles and melatonin rhythms/levels in a heterogeneous manner, and model organisms used to study these disorders appear to support that circadian dysfunction may be an inherent characteristic of neurodevelopmental disorders. Furthermore, the pre-clinical and clinical evidence indicates that circadian disruption at the environmental and genetic levels may contribute to the behavioural changes observed in these disorders. Finally, studies suggest that psychiatric medications, particularly those prescribed for attention-deficit/hyperactivity disorder and schizophrenia, can have direct effects on the circadian system and that chronotherapy may be leveraged to offset some of these side effects. This review highlights that circadian system dysfunction is likely a core pathological feature of neurodevelopmental disorders and that further research is required to elucidate this relationship.

Human Derived Dermal Fibroblasts as in Vitro Research Tool to Study Circadian Rhythmicity in Psychiatric Disorders

A number of psychiatric disorders are defined by persistent or recurrent sleep-wake disturbances alongside disruptions in circadian rhythm and altered clock gene expression. Circadian rhythms are present not only in the hypothalamic suprachiasmatic nucleus but also in peripheral tissues. In this respect, cultures of human derived dermal fibroblasts may serve as a promising new tool to investigate cellular and molecular mechanisms underlying the pathophysiology of mental illness. In this article, we discuss the advantages of fibroblast cultures to study psychiatric disease. More specifically, we provide an update on recent advances in modeling circadian rhythm disorders using human fibroblasts.

Evaluation of the Regulatory Role of Circadian Rhythm Related Long Non-Coding RNAs in ADHD Etiogenesis

OBJECTIVE

ADHD is associated with increased sleep problems and circadian rhythm disturbances. This study aimed to examine ADHD patients and healthy controls in terms of chronotypic features and expression levels of CLOCK, PER1, lncRNA HULC, lncRNA UCA1.

METHOD

Eighty-three children were included (43 ADHD). Conner's Parent Rating Scale-Revised Short Form, Childhood Chronotype Questionnaire, Children's Sleep Disorders Scale were administered. Gene expression levels were studied from peripheral blood.

RESULTS

Evening chronotype, sleep initiation/maintenance disorder, sleep-wake transition disorder, excessive sleepiness disorder were higher in the ADHD group compared to the controls in the scales reported by the parents. Expression levels of all examined genes were statistically significantly higher in the ADHD group. There was no significant relationship between genes and sleep parameters in the ADHD group.

CONCLUSION

Our study provides the first evidence that lncRNA HULC and lncRNA UCA1 might have a role in the etiology of ADHD.

Clock Genes Profiles as Diagnostic Tool in (Childhood) ADHD—A Pilot Study

Attention deficit hyperactivity disorder (ADHD) is a very common disorder in children and adults. A connection with sleep disorders, and above all, disorders of the circadian rhythm are the subject of research and debate. The circadian system can be represented on different levels. There have been a variety of studies examining 24-h rhythms at the behavioral and endocrine level. At the molecular level, these rhythms are based on a series of feedback loops of core clock genes and proteins. In this paper, we compared the circadian rhythms at the behavioral, endocrine, and molecular levels between children with ADHD and age- and BMI-matched controls, complementing the previous data in adults. In a minimally invasive setting, sleep was assessed via a questionnaire, actigraphy was used to determine the motor activity and light exposure, saliva samples were taken to assess the 24-h profiles of cortisol and melatonin, and buccal mucosa swaps were taken to assess the expression of the clock genes BMAL1 and PER2. We found significant group differences in sleep onset and sleep duration, cortisol secretion profiles, and in the expression of both clock genes. Our data suggest that the analysis of circadian molecular rhythms may provide a new approach for diagnosing ADHD in children and adults.

Sleep-related traits and attention-deficit/hyperactivity disorder comorbidity: Shared genetic risk factors, molecular mechanisms, and causal effects

OBJECTIVES

To evaluate the shared genetic components, common pathways and causal relationship between ADHD and sleep-related phenotypes.

METHODS

We used the largest genome-wide association summary statistics available for attention-deficit/hyperactivity disorder (ADHD) and various sleep-related phenotypes (insomnia, napping, daytime dozing, snoring, ease getting up, daytime sleepiness, sleep duration and chronotype). We estimated the genomic correlation using cross-trait linkage disequilibrium score regression (LDSR) and investigated the potential common mechanisms using gene-based cross-trait metanalyses and functional enrichment analyses. The causal effect was estimated using two-sample Mendelian randomisation (TSMR), using the inverse variance weighted method as the main estimator.

RESULTS

A positive genomic correlation between insomnia, daytime napping, daytime dozing, snoring, daytime sleepiness, short and long sleep duration, and ADHD was observed. Insomnia, daytime sleepiness, and snoring shared genes with ADHD, that are involved in neurobiological functions and regulatory signalling pathways. The TSMR supported a causal effect of insomnia, daytime napping, and short sleep duration on ADHD, and of ADHD on long sleep duration and chronotype.

CONCLUSION

Comorbidity between sleep phenotypes and ADHD may be mediated by common genetic factors that play an important role in neuronal signalling pathways. A causal effect of sleep disturbances and short sleep duration on ADHD reinforced their role as predictors of ADHD.

Atomoxetine and circadian gene expression in human dermal fibroblasts from study participants with a diagnosis of attention-deficit hyperactivity disorder

Atomoxetine (ATO) is a second line medication for attention-deficit hyperactivity disorder (ADHD). We proposed that part of the therapeutic profile of ATO may be through circadian rhythm modulation. Thus, the aim of this study was to investigate the circadian gene expression in primary human-derived dermal fibroblast cultures (HDF) after ATO exposure. We analyzed circadian preference, behavioral circadian and sleep parameters as well as the circadian gene expression in a cohort of healthy controls and participants with a diagnosis of ADHD. Circadian preference was evaluated with German Morningness-Eveningness-Questionnaire (D-MEQ) and rhythms of sleep/wake behavior were assessed via actigraphy. After ex vivo exposure to different ATO concentrations in HDF cultures, the rhythmicity of circadian gene expression was analyzed via qRT-PCR. No statistical significant effect of both groups (healthy controls, ADHD group) for mid-sleep on weekend days, mid-sleep on weekdays, social jetlag, sleep WASO and total number of wake bouts was observed. D-MEQ scores indicated that healthy controls had no evening preference, whereas subjects with ADHD displayed both definitive and moderate evening preferences. ATO induced the rhythmicity of Clock in the ADHD group. This effect, however, was not observed in HDF cultures of healthy controls. Bmal1 and Per2 expression showed a significant ZT × group interaction via mixed ANOVA. Strong positive correlations for chronotype and circadian genes were observed for Bmal1, Cry1 and Per3 among the study participants. Statistical significant different Clock, Bmal1 and Per3 expressions were observed in HDFs exposed to ATO collected from ADHD participants exhibiting neutral and moderate evening preference, as well as healthy participants with morning preferences. The results of the present study illustrate that ATO impacts on circadian function, particularly on Clock, Bmal1 and Per2 gene expression.

Synergistic efficacy and diminished adverse effect profile of composite treatment of several ADHD medications

Although attention-deficit/hyperactivity disorder (ADHD) is widely studied, problems regarding the adverse effect risks and non-responder problems still need to be addressed. Combination pharmacotherapy using standard dose regimens of existing medication is currently being practiced mainly to augment the therapeutic efficacy of each drug. The idea of combining different pharmacotherapies with different molecular targets to alleviate the symptoms of ADHD and its comorbidities requires scientific evidence, necessitating the investigation of their therapeutic efficacy and the mechanisms underlying the professed synergistic effects. Here, we injected male ICR mice with MK-801 to induce ADHD behavioral condition. We then modeled a "combined drug" using sub-optimal doses of methylphenidate, atomoxetine, and fluoxetine and investigated the combined treatment effects in MK-801-treated mice. No sub-optimal dose monotherapy alleviated ADHD behavioral condition in MK-801-treated mice. However, treatment with the combined drug attenuated the impaired behavior of MK-801-treated animals. Growth impediment, sleep disturbances, or risk of substance abuse were not observed in mice treated subchronically with the combined drugs. Finally, we observed that the combined ADHD drug rescued alterations in p-AKT and p-ERK1/2 levels in the prefrontal cortex and hippocampus, respectively, of MK-801-treated mice. Our results provide experimental evidence of a possible new pharmacotherapy option in ameliorating the ADHD behavioral condition without the expected adverse effects. The detailed mechanism of action underlying the synergistic therapeutic efficacy and reduced adverse reaction by combinatorial drug treatment should be investigated further in future studies.

Relationships Among Delayed Sleep Phase Disorder, Emotional Dysregulation, and Affective Temperaments in Adults With Attention Deficit Hyperactivity Disorder and Cyclothymia

This study aims to explore the relationships between delayed sleep phase disorder (DSPD) and emotional dysregulation in 240 patients (134 with cyclothymia, 81 with attention deficit hyperactivity disorder [ADHD] and 25 with both conditions). DSPD was assessed using the Morningness-Eveningness Questionnaire, followed by a clinical evaluation. Affective temperaments and emotional dysregulation were also investigated through the brief version of the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego and the Reactivity, Intensity, Polarity, Stability questionnaires, respectively. Clinical variables were compared in patients with and without DSPD, and a logistic regression model was used to identify the predictive value of the clinical characteristics on the presence of DSPD. DSPD patients (19% of the total sample) were significantly younger than patients without DSPD, showed an about 4 times higher lifetime history of comorbid ADHD and cyclothymia, and reported higher scores in the irritable and cyclothymic temperamental subscales and in the affective instability and impulsivity dimensions. In the multiple logistic regression, we found a negative predictive value of increasing age on the presence of DSPD, whereas comorbid cyclothymia and ADHD and cyclothymic temperament seem to represent risk factors for DSPD.

New Insights Into the Circadian Rhythm and Its Related Diseases

Circadian rhythms (CR) are a series of endogenous autonomous oscillators generated by the molecular circadian clock which acting on coordinating internal time with the external environment in a 24-h daily cycle. The circadian clock system is a major regulatory factor for nearly all physiological activities and its disorder has severe consequences on human health. CR disruption is a common issue in modern society, and researches about people with jet lag or shift works have revealed that CR disruption can cause cognitive impairment, psychiatric illness, metabolic syndrome, dysplasia, and cancer. In this review, we summarized the synchronizers and the synchronization methods used in experimental research, and introduced CR monitoring and detection methods. Moreover, we evaluated conventional CR databases, and analyzed experiments that characterized the underlying causes of CR disorder. Finally, we further discussed the latest developments in understanding of CR disruption, and how it may be relevant to health and disease. Briefly, this review aimed to synthesize previous studies to aid in future studies of CR and CR-related diseases.

Impact of adult attention deficit hyperactivity disorder and medication status on sleep/wake behavior and molecular circadian rhythms

Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric condition that has been strongly associated with changes in sleep and circadian rhythms. Circadian rhythms are near 24-h cycles that are primarily generated by an endogenous circadian timekeeping system, encoded at the molecular level by a panel of clock genes. Stimulant and non-stimulant medication used in the management of ADHD has been shown to potentially impact on circadian processes and their behavioral outputs. In the current study, we have analyzed circadian rhythms in daily activity and sleep, and the circadian gene expression in a cohort of healthy controls (N = 22), ADHD participants not using ADHD-medication (N = 17), and participants with ADHD and current use of ADHD medication (N = 17). Rhythms of sleep/wake behavior were assessed via wrist-worn actigraphy, whilst rhythms of circadian gene expression were assessed ex-vivo in primary human-derived dermal fibroblast cultures. Behavioral data indicate that patients with ADHD using ADHD-medication have lower relative amplitudes of diurnal activity rhythms, lower sleep efficiency, more nocturnal activity but not more nocturnal wakenings than both controls and ADHD participants without medication. At the molecular level, there were alterations in the expression of PER2 and CRY1 between ADHD individuals with no medication compared to medicated ADHD patients or controls, whilst CLOCK expression was altered in patients with ADHD and current medication. Analysis of fibroblasts transfected with a BMAL1:luc reporter showed changes in the timing of the peak expression across the three groups. Taken together, these data support the contention that both ADHD and medication status impact on circadian processes.

CLOCK Polymorphisms in Attention-Deficit/Hyperactivity Disorder (ADHD): Further Evidence Linking Sleep and Circadian Disturbances and ADHD

Circadian and sleep disorders, short sleep duration, and evening chronotype are often present in attention-deficit/hyperactivity disorder (ADHD). CLOCK, considered the master gene in the circadian rhythm, has been explored by few studies. Understanding the relationship between ADHD and CLOCK may provide additional information to understand the correlation between ADHD and sleep problems. In this study, we aimed to explore the association between ADHD and CLOCK, using several genetic markers to comprehensively cover the gene extension. A total of 259 ADHD children and their parents from a Brazilian clinical sample were genotyped for eight single nucleotide polymorphisms (SNPs) in the CLOCK locus. We tested the individual markers and the haplotype effects using binary logistic regression. Binary logistic and linear regressions considering ADHD symptoms among ADHD cases were conducted as secondary analysis. As main result, the analysis showed a risk effect of the G-A-T-G-G-C-G-A (rs534654, rs1801260, rs6855837, rs34897046, rs11931061, rs3817444, rs4864548, rs726967) haplotype on ADHD. A suggestive association between ADHD and rs534654 was observed. The results suggest that the genetic susceptibility to circadian rhythm attributed to the CLOCK gene may play an important role on ADHD.

β-Adrenergic receptors control brown adipose UCP-1 tone and cold response without affecting its circadian rhythmicity

Brown adipose tissue (BAT) thermogenic functions are primarily mediated by uncoupling protein (UCP)-1. Ucp1 gene expression is highly induced by cold temperature, via sympathetic nervous system and β-adrenergic receptors (βARs). Ucp1 is also repressed by the clock gene Rev-erbα, contributing to its circadian rhythmicity. In this study, we investigated mice lacking βARs (β-less mice) to test the relationship between βAR signaling and the BAT molecular clock. We found that in addition to controlling the induction of Ucp1 and other key BAT genes at near freezing temperatures, βARs are essential for the basal expression of BAT Ucp1 at room temperature. Remarkably, although basal Ucp1 expression is low throughout day and night in β-less mice, the circadian rhythmicity of Ucp1 and clock genes in BAT is maintained. Thus, the requirement of βAR signaling for BAT activity is independent of the circadian rhythmicity of Ucp1 expression and circadian oscillation of the molecular clock genes. On the other hand, we found that βARs are essential for the normal circadian rhythms of locomotor activity. Our results demonstrate that in addition to controlling the BAT response to extreme cold, βAR signaling is necessary to maintain basal Ucp1 tone and to couple BAT circadian rhythmicity to the central clock.-Razzoli, M., Emmett, M. J., Lazar, M. A., Bartolomucci, A. β-Adrenergic receptors control brown adipose UCP-1 tone and cold response without affecting its circadian rhythmicity.

Limited evidence for affective and diurnal rhythm responses to dim light-at-night in male and female C57Bl/6 mice

Circadian rhythms are recurring patterns in a range of behavioural, physiological and molecular parameters that display periods of near 24 h, and are underpinned by an endogenous biological timekeeping system. Circadian clocks are increasingly recognised as being key for health. Environmental light is the key stimulus that synchronises the internal circadian system with the external time cues. There are emergent health concerns regarding increasing worldwide prevalence of electric lighting, especially man-made light-at-night, and light's impact on the circadian system may be central to these effects. A number of previous studies have demonstrated increased depression-like behaviour in various rodent experimental models exposed to dim light-at-night. In this study we set out to study the impact of dim light-at-night on circadian and affective behaviours in C57Bl/6 mice. We set out specifically to examine the impact of sex on light at night's effects, as well as the impact of housing conditions. We report minimal impact of light-at-night on circadian and affective behaviours, as measured by the tail suspension test, the forced swim test, the sucrose preference test and the elevated plus maze. Light-at-night was also not associated with an increase in body weight, but was associated with a decrease in the cell proliferation marker Ki-67 in the dentate gyrus. In summary, we conclude that experimental contextual factors, such as model species or strain, may be considerable importance in the investigation of the impact of light at night on mood-related parameters.

The role of CLOCK gene in psychiatric disorders: Evidence from human and animal research

The circadian clock system drives daily rhythms in physiology, metabolism, and behavior in mammals. Molecular mechanisms of this system consist of multiple clock genes, with Circadian Locomotor Output Cycles Kaput (CLOCK) as a core member that plays an important role in a wide range of behaviors. Alterations in the CLOCK gene are associated with common psychiatric disorders as well as with circadian disturbances comorbidities. This review addresses animal, molecular, and genetic studies evaluating the role of the CLOCK gene on many psychiatric conditions, namely autism spectrum disorder, schizophrenia, attention-deficit/hyperactivity disorder, major depressive disorder, bipolar disorder, anxiety disorder, and substance use disorder. Many animal experiments focusing on the effects of the Clock gene in behavior related to psychiatric conditions have shown consistent biological plausibility and promising findings. In humans, genetic and gene expression studies regarding disorder susceptibility, sleep disturbances related comorbidities, and response to pharmacological treatment, in general, are in agreement with animal studies. However, the number of controversial results is high. Literature suggests that the CLOCK gene exerts important influence on these conditions, and influences the susceptibility to phenotypes of psychiatric disorders.

Sleep and Circadian Rhythmicity in Adult ADHD and the Effect of Stimulants

OBJECTIVE

This review updates information on sleep and circadian rhythmicity in adult ADHD, especially circadian rhythmicity and the influence of stimulants.

METHOD

Investigations into sleep, chronotype, and circadian rhythm in adult ADHD were searched in the Cochrane Library, Embase, Medline, and PsycInfo databases.

RESULTS

ADHD in adults is associated with longer objective sleep latency, irrespective of insomnia complaints. Sleep maintenance is disturbed and waking up time is delayed. Adult ADHD is associated with increased eveningness, delayed dim light melatonin onset (DLMO), and later waking up time. Stimulant treatment induces delay of nonparametric circadian parameters, whereas light therapy (LT) induces shifts toward morningness, which is associated with a reduction of ADHD symptoms.

CONCLUSION

Adult ADHD is associated with delayed circadian rhythmicity and analogous sleep characteristics, which are typical of a delayed sleep phase disorder. Stimulants induce delay of circadian rhythmicity.

Alterations of the circadian system in Parkinson's disease patients

Alterations of circadian rhythms are among the most debilitating non-motor symptoms in Parkinson's Disease (PD). Although a growing awareness towards these symptoms has occurred during the last decade, their underlying neuropathophysiology remains poorly understood and consequently no effective therapeutic strategies are available to alleviate these problems. Recent studies have investigated multiple circadian rhythms at different stages of PD. The advances made have allowed an accurate evaluation of the affected underlying pathways and mechanisms. Here I dissect, over disease progression, the relative causal contribution to health impairments in PD patients of dysfunctions in the different components of the neural network governing circadian rhythms. A deeper understanding of these mechanisms will provide not only a greater understanding of disease neuropathology, but also hold the promise for effective therapies. © 2016 International Parkinson and Movement Disorder Society.

Circadian rhythms and attention deficit hyperactivity disorder: The what, the when and the why

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental condition characterised by impulsivity, inattention and hyperactivity. Aside from these core psychopathologies, sleep disturbances are found to be highly comorbid with ADHD, and indeed dysregulated sleep may contribute to some of the symptoms of the disorder. It is not clear how sleep disturbances come to be so common in ADHD, but one putative mechanism is through the circadian timekeeping system. This system underpins the generation of near 24-hour rhythms in a host of physiological, behavioural and psychological parameters, and is a key determinant of the sleep/wake cycle. In this paper we review the evidence for sleep and circadian rhythm disturbance in ADHD, examine the possible mechanistic links between these factors and the disorder and discuss future directions through which the circadian clock can be targetted for ADHD symptom relief.

Sleep in children with attention-deficit/hyperactivity disorder (ADHD) before and after 6-month treatment with methylphenidate: a pilot study

Children with ADHD may present with sleep disturbances that add to the impairment of the disorder. The long-term sleep effects of the first-line pharmacological treatment for ADHD, i.e., psychostimulants, are unclear. In this pilot study, we compared polysomnographic variables in children with ADHD (n = 11, aged 6-15 years), before pharmacological treatment, and in children without ADHD (n = 22, aged 5-14 years); we also assessed polysomnographic changes in children with ADHD (n = 7) after a 6-month treatment with methylphenidate immediate-release (once or twice daily). Compared to children without ADHD, those with ADHD at baseline presented with significantly increased duration of awakenings (p = 0.02), reduction in sleep efficiency (p = 0.03), and increase in stage I (N1) (p < 0.01) and reduction in stage II (N2) (p = 0.02) and stage III-IV (N3) percentages. Methylphenidate treatment did not significantly change any parameter of sleep architecture.

CONCLUSION

Preliminary evidence from this pilot study shows that, compared to children without ADHD, those with ADHD presented a more fragmented and less effective sleep at baseline and that the 6-month methylphenidate treatment did not further negatively impact on sleep architecture.

WHAT IS KNOWN

• Children with ADHD may present with subjectively reported and/or objectively confirmed disturbances of sleep. • The long-term effects on sleep of the first-line pharmacological treatment for ADHD, i.e., psychostimulants, are not clear. What is new: • Our study showed that the 6-month continuous treatment with methylphenidate did not further negatively impact on sleep architecture in children with ADHD.

The effects of atomoxetine and methylphenidate on the prepulse inhibition of the acoustic startle response in mice

Atomoxetine (ATM) and methylphenidate (MPD) have been used for the treatment of attention deficit hyperactivity disorder (ADHD). ATM is a selective norepinephrine reuptake inhibitor, whereas MPD is a psychostimulant and acts as a norepinephrine and dopamine reuptake inhibitor. In the present study, we investigated the effects of ATM (1, 3 or 10mg/kg) and MPD (5, 10 or 20mg/kg) on pharmacological mouse models of sensorimotor gating measured by prepulse inhibition (PPI) using the acoustic startle response test. MK-801, a non-competitive N-methyl-d-aspartate receptor antagonist, or apomorphine, a non-competitive dopamine receptor agonist, was used to induce PPI deficits. ATM (3 or 10mg/kg, s.c.) significantly attenuated the MK-801-, but not apomorphine-, induced PPI deficits. In contrast to ATM, MPD did not reverse the PPI deficits induced by either MK-801 or apomorphine. Immunostaining revealed that the number of c-Fos-immunopositive cells was increased in the nucleus accumbens following MK-801 treatment, and this was reversed by the administration of ATM (3mg/kg), but not MPD (10mg/kg). However, neither ATM nor MPD reversed the increased number of c-Fos-immunopositive cells in the nucleus accumbens following apomorphine treatment. These results suggest that the attenuating effect of ATM on the increased c-Fos immunoreactivity in the nucleus accumbens induced by MK-801 may be attributed to the PPI deficit-ameliorating effects of ATM and that ATM would be useful to treat sensorimotor gating-related disorders by improving the patient's attention span or cognitive function.

Circadian clock and stress interactions in the molecular biology of psychiatric disorders

Many psychiatric disorders are characterized by circadian rhythm abnormalities, including disturbed sleep/wake cycles, changes in locomotor activity, and abnormal endocrine function. Animal models with mutations in circadian "clock genes" commonly show disturbances in reward processing, locomotor activity and novelty seeking behaviors, further supporting the idea of a connection between the circadian clock and psychiatric disorders. However, if circadian clock dysfunction is a common risk factor for multiple psychiatric disorders, it is unknown if and how these putative clock abnormalities could be expressed differently, and contribute to multiple, distinct phenotypes. One possible explanation is that the circadian clock modulates the biological responses to stressful environmental factors that vary with an individual's experience. It is known that the circadian clock and the stress response systems are closely related: Circadian clock genes regulate the physiological sensitivity to and rhythmic release of glucocorticoids (GC). In turn, GCs have reciprocal effects on the clock. Since stressful life events or increased vulnerability to stress are risk factors for multiple psychiatric disorders, including post-traumatic stress disorder (PTSD), attention deficit hyperactivity disorder (ADHD), bipolar disorder (BD), major depressive disorder (MDD), alcohol use disorder (AUD) and schizophrenia (SCZ), we propose that modulation of the stress response is a common mechanism by which circadian clock genes affect these illnesses. Presently, we review how molecular components of the circadian clock may contribute to these six psychiatric disorders, and present the hypothesis that modulation of the stress response may constitute a common mechanism by which the circadian clock affects multiple psychiatric disorders.

Long-lasting effects of sepsis on circadian rhythms in the mouse

Daily patterns of activity and physiology are termed circadian rhythms and are driven primarily by an endogenous biological timekeeping system, with the master clock located in the suprachiasmatic nucleus. Previous studies have indicated reciprocal relationships between the circadian and the immune systems, although to date there have been only limited explorations of the long-term modulation of the circadian system by immune challenge, and it is to this question that we addressed ourselves in the current study. Sepsis was induced by peripheral treatment with lipopolysaccharide (5 mg/kg) and circadian rhythms were monitored following recovery. The basic parameters of circadian rhythmicity (free-running period and rhythm amplitude, entrainment to a light/dark cycle) were unaltered in post-septic animals compared to controls. Animals previously treated with LPS showed accelerated re-entrainment to a 6 hour advance of the light/dark cycle, and showed larger phase advances induced by photic stimulation in the late night phase. Photic induction of the immediate early genes c-FOS, EGR-1 and ARC was not altered, and neither was phase-shifting in response to treatment with the 5-HT-1a/7 agonist 8-OH-DPAT. Circadian expression of the clock gene product PER2 was altered in the suprachiasmatic nucleus of post-septic animals, and PER1 and PER2 expression patterns were altered also in the hippocampus. Examination of the suprachiasmatic nucleus 3 months after treatment with LPS showed persistent upregulation of the microglial markers CD-11b and F4/80, but no changes in the expression of various neuropeptides, cytokines, and intracellular signallers. The effects of sepsis on circadian rhythms does not seem to be driven by cell death, as 24 hours after LPS treatment there was no evidence for apoptosis in the suprachiasmatic nucleus as judged by TUNEL and cleaved-caspase 3 staining. Overall these data provide novel insight into how septic shock exerts chronic effects on the mammalian circadian system.

Methylphenidate modifies the motion of the circadian clock

People with attention-deficit/hyperactivity disorder (ADHD) often experience sleep problems, and these are frequently exacerbated by the methylphenidate they take to manage their ADHD symptoms. Many of the changes to sleep are consistent with a change in the underlying circadian clock. The present study was designed to determine if methylphenidate alone could alter properties of the circadian clock. Young male mice were examined in light-dark cycles and in constant darkness and recordings were performed on behavioral activity, sleep, and electrical activity in the suprachiasmatic nucleus (SCN) of freely moving mice. Methylphenidate in the drinking water (0.08%) significantly increased activity in the mid-to-late night, and led to a delay in the onset of activity and sleep relative to the light-dark cycle. While locomotor levels returned to baseline after treatment ended, the phase angle of entrainment required at least a week to return to baseline levels. In constant darkness, the free-running period of both wheel-running and general locomotor rhythms was lengthened by methylphenidate. When the treatment ended, the free-running period either remained stable or only partially reverted to baseline levels. Methylphenidate also altered the electrical firing rate rhythms in the SCN. It induced a delay in the trough of the rhythm, an increment in rhythm amplitude, and a reduction in rhythm variability. These observations suggest that methylphenidate alters the underlying circadian clock. The observed changes are consistent with clock alterations that would promote sleep-onset insomnia.

Neuroimmunomodulation in unipolar depression: a focus on chronobiology and chronotherapeutics

The rising burden of unipolar depression along with its often related sleep disturbances, as well as increasing rates of sleep restriction in modern society, make the search for an extended understanding of the aetiology and pathophysiology of depression necessary. Accumulating evidence suggests an important role for the immune system in mediating disrupted neurobiological and chronobiological processes in depression. This review aims to provide an overview of the neuroimmunomodulatory processes involved with depression and antidepressant treatments with a special focus on chronobiology, chronotherapeutics and the emerging field of immune-circadian bi-directional crosstalk. Increasing evidence suggests that chronobiological disruption can mediate immune changes in depression, and likewise, immune processes can mediate chronobiological disruption. This may suggest a bi-directional relationship in immune-circadian crosstalk. Furthermore, given the immunomodulatory effects of antidepressants and chronotherapeutics, as well as their associated beneficial effects on circadian disturbance, we--and others--suggest that these therapeutic agents may exert their chronobiotic effects partially via the neuroimmune system. Further research is required to better elucidate the mechanisms of immune involvement in the chronobiology of depression.