The Neurobiology of Sleep and Wakefulness

A Double-Blind, Placebo-Controlled, Phase II Study to Determine the Efficacy, Safety, Tolerability and Pharmacokinetics of a Controlled Release (CR) Formulation of Mazindol in Adults with DSM-5 Attention-Deficit/Hyperactivity Disorder (ADHD)

BACKGROUND

Mazindol is under investigation for the treatment of attention-deficit/hyperactivity disorder (ADHD) because of its alertness-enhancing properties. A novel controlled-release (CR) formulation of mazindol was developed to allow once-daily dosing.

OBJECTIVE

The aim of this study was to evaluate the efficacy of mazindol CR in adults with ADHD.

DESIGN

We conducted a randomized, double-blind, placebo-controlled 6-week trial.

METHODS

Subjects diagnosed with ADHD using the Mini-International Neuropsychiatric Structured Interview (MINI) and with an ADHD Rating Scale, Diagnostic and Statistical Manual of Mental Disorders 5th Edition (ADHD-RS-DSM5) score ≥ 28 were randomized to receive placebo or 1-3 mg/day of mazindol for 6 weeks. The primary endpoint was the reduction from baseline in the ADHD-RS-DSM5 score on Day 42. Secondary endpoints were response rates defined by change in ADHD-RS-DSM5 (≥ 30 or ≥ 50% reduction) and dichotomized Clinical Global Impression-Improvement (CGI-I) score (1 or 2). An exploratory endpoint of functional impairment, as measured by the Target Impairment Scale, examined individualized deficits in specific settings. Safety, tolerability, and pharmacokinetics were assessed.

RESULTS

Eighty-five participants were randomized (n = 43 active, 42 placebo); 75 completed. Weekly ADHD-RS-DSM5 measurements after mazindol differed from placebo beginning at Day 7, with a least squares mean difference (active-placebo) of - 13.2 at Day 42 and an effect size of 1.09. For the 30% or more reduction in ADHD-RS-DSM5 (minimal response), a significant difference (active-placebo) was seen starting at Day 7 and continuing to Day 42. For the CGI-I (1 or 2) and for the 50% or more reduction in ADHD-RS-DSM5 (measures of excellent response), the differences began at Day 14 and continued to Day 42. Functional impairment was significantly different in the proportion achieving at least a 50% reduction in target impairment score (42.9% mazindol vs 11.9% placebo) by Day 42. Dry mouth, nausea, fatigue, heart rate (HR) increased, decreased appetite, and constipation were more prevalent for mazindol versus placebo. Overall, mazindol CR had minimal effects on blood pressure and small effects on HR.

CONCLUSION

Mazindol CR was efficacious in the treatment of adults with ADHD, with a large effect size, and was well tolerated, supporting the progression to phase III. (Clinicaltrials.gov Registration No. NCT02808104).

In Search of a Good Night's Sleep

A good night's sleep is essential to overall physical, cognitive, and emotional well-being. Sleep deprivation, whether general or related to time changes (e.g., daylight saving time), contributes to decreased cognition, impaired memory, poor coordination, mood fluctuations, increased risk of heart disease and diabetes, and weight gain, among others. The sleep cycle is defined by five stages and two distinct parts-rapid eye movement (REM) and non-REM sleep-that work to promote not only the quantity of sleep but also the quality of sleep, which impacts overall health. Each stage of sleep is influenced by various neurochemical actions among the brain regions. The neurochemistry and neuropath-ways related to the sleep/wake cycle as well as the mechanisms of action of sleep-inducing and wake-promoting medications are explored. [Journal of Psychosocial Nursing and Mental Health Services, 55(10), 19-26.].

Mapping the Hypocretin/Orexin Neuronal System: An Unexpectedly Productive Journey

Early in 1998, we (de Lecea et al., 1998) and others (Sakurai et al., 1998) described the same hypothalamic neuropeptides, respectively called the hypocretins or orexins, which were discovered using two different approaches. In December of that year, we published the subject of this commentary in the Journal of Neuroscience: a highly detailed anatomical description of the extensive axonal projections of the hypocretin/orexin neurons. Although the function of this system was unknown at the time, a large body of literature today attests that the hypocretin/orexin neuropeptides play important roles in multiple physiological functions, particularly in sleep/wake regulation. Neuroanatomical studies are rarely frontline news, but the citation rate of this paper underscores the critical nature of such basic research. Based in part on this detailed description, the hypocretin/orexin neuropeptides have since been studied in many different areas of neuroscience research, including sleep/wake regulation, feeding, addiction, reward and motivation, anxiety and depression, cardiovascular regulation, pain, migraine, and neuroendocrine regulation, including reproduction. Thus, this paper has had a surprisingly broad impact on neuroscience research, particularly since it was originally rejected by the Journal!

Neuronal substrates of sleep homeostasis; lessons from flies, rats and mice

Sleep homeostasis is a fundamental property of vigilance state regulation that is highly conserved across species. Neuronal systems and circuits that underlie sleep homeostasis are not well understood. In Drosophila, a neuronal circuit involving neurons in the ellipsoid body and in the dorsal Fan-shaped body is a candidate for both tracing sleep need during waking and translating it to increased sleep drive and expression. Sleep homeostasis in rats and mice involves multiple neuromodulators acting on multiple wake- and sleep-promoting neuronal systems. A functional central homeostat emerges from A₁ receptor mediated actions of adenosine on wake-promoting neurons in the basal forebrain and hypothalamus, and A_2A adenosine receptor-mediated actions on sleep-promoting neurons in the preoptic hypothalamus and nucleus accumbens.

Neural oscillations demonstrate that general anesthesia and sedative states are neurophysiologically distinct from sleep

General anesthesia is a man-made neurophysiological state comprised of unconsciousness, amnesia, analgesia, and immobility along with maintenance of physiological stability. Growing evidence suggests that anesthetic-induced neural oscillations are a primary mechanism of anesthetic action. Each anesthetic drug class produces distinct oscillatory dynamics that can be related to the circuit mechanisms of drug action. Sleep is a naturally occurring state of decreased arousal that is essential for normal health. Physiological measurements (electrooculogram, electromyogram) and neural oscillatory (electroencephalogram) dynamics are used to empirically characterize sleep into rapid eye movement sleep and the three stages of non-rapid eye movement sleep. In this review, we discuss the differences between anesthesia- and sleep-induced altered states from the perspective of neural oscillations.

Lack of Responsiveness during the Onset and Offset of Sevoflurane Anesthesia Is Associated with Decreased Awake-Alpha Oscillation Power

Anesthetic drugs are typically administered to induce altered states of arousal that range from sedation to general anesthesia (GA). Systems neuroscience studies are currently being used to investigate the neural circuit mechanisms of anesthesia-induced altered arousal states. These studies suggest that by disrupting the oscillatory dynamics that are associated with arousal states, anesthesia-induced oscillations are a putative mechanism through which anesthetic drugs produce altered states of arousal. However, an empirical clinical observation is that even at relatively stable anesthetic doses, patients are sometimes intermittently responsive to verbal commands during states of light sedation. During these periods, prominent anesthesia-induced neural oscillations such as slow-delta (0.1–4 Hz) oscillations are notably absent. Neural correlates of intermittent responsiveness during light sedation have been insufficiently investigated. A principled understanding of the neural correlates of intermittent responsiveness may fundamentally advance our understanding of neural dynamics that are essential for maintaining arousal states, and how they are disrupted by anesthetics. Therefore, we performed a high-density (128 channels) electroencephalogram (EEG) study (n = 8) of sevoflurane-induced altered arousal in healthy volunteers. We administered temporally precise behavioral stimuli every 5 s to assess responsiveness. Here, we show that decreased eyes-closed, awake-alpha (8–12 Hz) oscillation power is associated with lack of responsiveness during sevoflurane effect-onset and -offset. We also show that anteriorization—the transition from occipitally dominant awake-alpha oscillations to frontally dominant anesthesia induced-alpha oscillations—is not a binary phenomenon. Rather, we suggest that periods, which were defined by lack of responsiveness, represent an intermediate brain state. We conclude that awake-alpha oscillation, previously thought to be an idling rhythm, is associated with responsiveness to behavioral stimuli.

Genetic Pathways to Insomnia

This review summarizes current research on the genetics of insomnia, as genetic contributions are thought to be important for insomnia etiology. We begin by providing an overview of genetic methods (both quantitative and measured gene), followed by a discussion of the insomnia genetics literature with regard to each of the following common methodologies: twin and family studies, candidate gene studies, and genome-wide association studies (GWAS). Next, we summarize the most recent gene identification efforts (primarily GWAS results) and propose several potential mechanisms through which identified genes may contribute to the disorder. Finally, we discuss new genetic approaches and how these may prove useful for insomnia, proposing an agenda for future insomnia genetics research.

Tenuifolin, a saponin derived from Radix Polygalae, exhibits sleep-enhancing effects in mice

BACKGROUND

Radix Polygalae, the dried root of Polygala tenuifolia, has been extensively used as a traditional Chinese medicine for promoting intelligence and tranquilization. Polygalasaponins extracted from the root of P. tenuifolia possess evident anxiolytic and sedative-hypnotic activities. Previous studies have reported that tenuifolin was a major constituent of polygalasaponins.

PURPOSE

The currently study aims to investigate the hypnotic effect and possible mechanism of tenuifolin in freely moving mice.

DESIGN/METHODS

The hypnotic effects of tenuifolin (20, 40 and 80mg/kg, p.o.) were assessed by electroencephalographic (EEG) and electromyographic (EMG) analysis. Double-staining immunohistochemistry test was performed to evaluate the neuronal activity of sleep-wake regulating brain areas. High performance liquid chromatograph- electrochemical detection (HPLC-ECD) and ultrafast liquid chromatography-mass spectrometry (UFLC-MS) were used for the detection of neurotransmitters. Locomotor activity was measured by Open-field Test.

RESULTS

Tenuifolin at doses of 40 and 80mg/kg (p.o.) significantly prolonged the total sleep time by increasing the amount of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, associated with the significant increase in the bouts of episodes respectively. After administration of tenuifolin, the cortical EEG power spectral densities during NREM and REM sleep were similar to that of natural sleep (vehicle) and thus compatible with physiological sleep. Double-immunohistochemistry staining test showed that tenuifolin increased the c-Fos positive ratios of GABAergic NREM sleep-promoting neurons in ventrolateral preoptic area (VLPO), cholinergic REM sleep-promoting neurons in laterodorsal tegmental area (LDT) and pontomesencephalic tegmental area (PPT) and decreased the c-Fos positive ratios in wake-promoting neurons (locus coeruleus (LC) and perifornical area (Pef)). Neurotransmitter detections revealed that tenuifolin significantly reduced the noradrenaline (NA) levels in LC, VLPO, PPT and LDT, elevated the GABA levels in VLPO, LC and Pef and increased the acetylcholine (Ach) levels in LDT and PPT. In addition, tenuifolin did not cause any change to locomotor activity.

CONCLUSION

Taken together, these results provide the first experimental evidence of the significant sleep-enhancing effect of tenuifolin in mice. This effect appears to be mediated, at least in part, by the activation of GABAergic systems and/or by the inhibition of noradrenergic systems. Moreover, this study adds new scientific evidence and highlights the therapeutic potential of the medicinal plant P. tenuifolia in the development of phytomedicines with hypnotic properties.

Sleep as spatiotemporal integration of biological processes that evolved to periodically reinforce neurodynamic and metabolic homeostasis: The 2m3d paradigm of sleep

Sleep continues to perplex scientists and researchers. Despite decades of sleep research, we still lack a clear understanding of the biological functions and evolution of sleep. In this review, we will examine sleep from a functional and phylogenetic perspective and describe some important conceptual gaps in understanding sleep. Classical theories of the biology and evolution of sleep emphasize sensory activation, energy balance, and metabolic homeostasis. Advances in electrophysiology, functional neuroimaging, and neuroplasticity allow us to view sleep within the framework of neural dynamics. With this paradigm shift, we have come to realize the importance of neurodynamic homeostasis in shaping the biology of sleep. Evidently, animals sleep to achieve neurodynamic and metabolic homeostasis. We are not aware of any framework for understanding sleep where neurodynamic, metabolic, homeostatic, chronophasic, and afferent variables are all taken into account. This motivated us to propose the two-mode three-drive (2m3d) paradigm of sleep. In the 2m3d paradigm, local neurodynamic/metabolic (N/M) processes switch between two modes-m0 and m1-in response to three drives-afferent, chronophasic, and homeostatic. The spatiotemporal integration of local m0/m1 operations gives rise to the global states of sleep and wakefulness. As a framework of evolution, the 2m3d paradigm allows us to view sleep as a robust adaptive strategy that evolved so animals can periodically reinforce neurodynamic and metabolic homeostasis while remaining sensitive to their internal and external environment.

The Neurobiology of Circadian Rhythms

There is a growing recognition that the coordinated timing of behavioral, physiologic, and metabolic circadian rhythms is a requirement for a healthy body and mind. In mammals, the primary circadian oscillator is the hypothalamic suprachiasmatic nucleus (SCN), which is responsible for circadian coordination throughout the organism. Temporal homeostasis is recognized as a complex interplay between rhythmic clock gene expression in brain regions outside the SCN and in peripheral organs. Abnormalities in this intricate circadian orchestration may alter sleep patterns and contribute to the pathophysiology of affective disorders.