Effect of psychostimulants on impulsivity and risk taking in narcolepsy with cataplexy

Determinants of substance use patterns in patients with narcolepsy type 1: A multi-center comparative cross-sectional study

OBJECTIVES

In this multi-center cross-sectional study, we compared substance use patterns (SUPs) between patients with narcolepsy type 1 (NT1) and controls, and investigated, among patients, factors associated with the consumption of the main psychoactive substances.

METHODS

Adult patients with NT1 and controls completed questionnaires about tobacco, alcohol, and cannabis use patterns. Unadjusted bivariable then multivariate analyses (adjusted for sex, age, education, family status, and depression) were performed to compare SUPs between controls and patients, and to explore socio-demographic, psycho-behavioral, and clinical determinants of consumptions.

RESULTS

We included 235 patients (63.8 % women, 36.4 ± 14.7 years) and 166 controls (69.9 % women, 40.3 ± 14.4 years). Substances co-consumptions were frequent in both groups. Patients with NT1 were more frequently current smokers (32.3 % vs. 20.1 %, p < 0.01) or e-cigarettes users (12.1 % vs 2.4 %, p < 0.001) than controls, while no difference was observed for cannabis use and alcohol misuse. Only the increased likelihood of vaping remained significant in adjusted analysis. Among NT1 patients, smoking was associated with disrupted nighttime sleep (OR[95%CI] = 2.28[1.02-5.12], p < 0.05) and less obesity (OR = 0.24[0.09-0.59], p < 0.05). Alcohol misuse was associated with sleep paralysis (OR = 2.11[1.13-3.91], p < 0.05) and treatments (modafinil: OR = 2.14[1.15-4.01], p < 0.05; sodium oxybate: OR = 0.41[0.17-0.97], p < 0.05). Tobacco and cannabis consumptions were associated with lower physical activity (OR = 0.46 [0.24-0.87], p < 0.05 and OR = 0.25[0.10-0.66], p < 0.01). Alcohol misuse and cannabis use were associated with rule breaking behaviors (OR = 5.89[1.61-21.60], p < 0.05 and OR = 8.52[1.79-40.48], p = 0.01).

CONCLUSION

Patients with NT1 do not seem less vulnerable to psychoactive substance use/misuse. Consumptions patterns are associated with multiple dimensions of the disease including sleep-related symptoms, comorbidities, treatments, and psycho-behavioral factors.

International Union of Basic and Clinical Pharmacology CXIV: Orexin Receptor Function, Nomenclature and Pharmacology

The orexin system consists of the peptide transmitters orexin-A and -B and the G protein-coupled orexin receptors OX1 and OX2 Orexin receptors are capable of coupling to all four families of heterotrimeric G proteins, and there are also other complex features of the orexin receptor signaling. The system was discovered 25 years ago and was immediately identified as a central regulator of sleep and wakefulness; this is exemplified by the symptomatology of the disorder narcolepsy with cataplexy, in which orexinergic neurons degenerate. Subsequent translation of these findings into drug discovery and development has resulted to date in three clinically used orexin receptor antagonists to treat insomnia. In addition to sleep and wakefulness, the orexin system appears to be a central player at least in addiction and reward, and has a role in depression, anxiety and pain gating. Additional antagonists and agonists are in development to treat, for instance, insomnia, narcolepsy with or without cataplexy and other disorders with excessive daytime sleepiness, depression with insomnia, anxiety, schizophrenia, as well as eating and substance use disorders. The orexin system has thus proved an important regulator of numerous neural functions and a valuable drug target. Orexin prepro-peptide and orexin receptors are also expressed outside the central nervous system, but their potential physiological roles there remain unknown. SIGNIFICANCE STATEMENT: The orexin system was discovered 25 years ago and immediately emerged as an essential sleep-wakefulness regulator. This discovery has tremendously increased the understanding of these processes and has thus far resulted in the market approval of three orexin receptor antagonists, which promote more physiological aspects of sleep than previous hypnotics. Further, orexin receptor agonists and antagonists with different pharmacodynamic properties are in development since research has revealed additional potential therapeutic indications. Orexin receptor signaling is complex and may represent novel features.

Altered reinforcement learning in Narcolepsy type I and other central disorders of hypersomnolence

Cognitive impairments are described in central disorders of hypersomnolence (CDH), but studies remain very limited and largely focused on narcolepsy type 1 (NT1). The precise nature and origin of these cognitive impairments is poorly understood. Specifically, impaired decision making under ambiguity has been reported in NT1 and suggested to be caused by dysregulation of the direct projections of hypocretin neurons to the dopamine network. However, the decision-making tasks used previously embed different cognitive functions that are difficult to isolate. This study aims to test reinforcement learning in participants with NT1 and with other (non-hypocretin deficient) CDH in a task known to directly depend on the dopamine system. Participants with NT1 (N = 27), other CDH (N = 34, including narcolepsy type 2 and idiopathic hypersomnia, matched with NT1 participants for sleepiness severity), and healthy participants (N = 34) took part in the study. Results showed that all groups had normal and similar positive reinforcement learning, a pattern not suggestive of dopamine deficiency. However, both participants with NT1 and other CDH had decreased learning abilities to avoid losses. This decreased negative reinforcement learning in participants with CDH was associated with the alteration of vigilance. This study provides new insights into the nature of decision making impairment in people with CDH and suggests that these alterations could be minimized by restoring adequate vigilance.

Priming effects of a slot machine game and amphetamine on probabilistic risk-taking in people with gambling disorder and healthy controls

INTRODUCTION

The Game of Dice Task (GDT) captures probabilistic risk-taking, which is an important feature of addictions and integral to gambling disorder (GD). No research appears to have assessed effects of gambling-specific priming manipulations or the pharmacological basis of such effects on the GDT.

AIMS

To investigate effects of slot machine gambling (Slots) and d-amphetamine (AMPH; 20 mg) on risk-taking in people with GD and healthy controls (HCs) (n = 30/group). The role of dopamine (DA) was assessed by pre-treating participants with the D2 receptor (D2R)-preferring antagonist, haloperidol (HAL; 3-mg) or mixed D1R-D2R antagonist, fluphenazine (FLU; 3-mg).

HYPOTHESES

Slots and AMPH will each increase risk-taking based on fewer (less probable) possible outcomes selected (POS) and poorer net monetary outcomes (NMO; gains minus losses) on the GDT, with stronger effects in Group GD. If DA mediates these effects, outcomes will vary with pre-treatment.

METHOD

Participants attended a pre-experimental baseline session and 4 test sessions. Antagonist Group (HAL, FLU) was manipulated between-participants. Pre-treatment (antagonist, placebo) was manipulated within-participants and counterbalanced over sessions for Slots and AMPH test phases. Moderator/mediator effects of trait and neuropsychological factors and GD severity (South Oaks Gambling Screen; SOGS) were explored via covariance.

RESULTS

AMPH led to an escalation in risky POS over trial blocks in both groups, regardless of pre-treatment. Cognitive inflexibility (high perseveration-proneness) moderated this effect in Group HC. In Group GD, SOGS selectively predicted riskier POS on AMPH sessions. Group GD achieved poorer NMO vs. Group HC on the pre-experimental baseline and Placebo-Slots sessions. Group HC selectively displayed poorer NMO on the Antagonist-Slots session.

CONCLUSIONS

The GDT can detect behavioral and pharmacological priming effects. Cognitive inflexibility and symptom severity moderate AMPH-induced risk-taking in HC and GD participants, respectively. Sensitization-related "wanting" of risk may contribute to the latter effect in people with GD.

Exploring Addictive Online Behaviors in Patients with Narcolepsy Type 1

BACKGROUND

Narcolepsy type 1 (NT1) is a rare neurological sleep disorder caused by the loss of neurons that produce hypocretin-a peptide that plays a crucial role in addictive behaviors. We aimed to compare, for the first time, levels of problematic online gaming, problematic social media use, and compulsive Internet use between NT1 patients and healthy controls (HC), and to evaluate the association between anxiety, depression, and emotion dysregulation with addictive online behaviors in NT1 patients.

METHODS

A total of 43 patients with NT1 and 86 sex- and age-matched HC participated in an online cross-sectional survey.

RESULTS

NT1 patients did not differ from HC in terms of problematic social media use and compulsive Internet use but displayed higher levels of problematic online gaming compared to HC. Higher levels of emotion dysregulation were significantly associated with higher levels of problematic social media use and compulsive Internet use, while none of the tested factors were associated with problematic online gaming.

CONCLUSION

NT1 patients and HC had similar levels of problematic social media use and compulsive Internet use, but NT1 patients showed higher levels of problematic online gaming. Emotion dysregulation might be an intervention target for reducing compulsive Internet use and problematic social media use.

Cognitive dysfunction in central disorders of hypersomnolence: A systematic review

Central disorders of hypersomnolence (CDH) are characterized by excessive daytime sleepiness not related to comorbid sleep or medical disturbances. We systematically examined scientific literature on cognitive functions in patients suffering from CDH. Forty-eight studies proved eligible and were analyzed separately for Narcolepsy Type 1 (NT1), Narcolepsy Type 2 (NT2), Idiopathic hypersomnia (IH) and Kleine-Levin syndrome (KLS). Results were grouped into the cognitive domains of attention, memory, executive functions and higher order cognition. Consistent attention impairments emerged in NT1, NT2 and IH patients, with NT1 patients showing the most compromised profile. Memory functions are largely unimpaired in CDH patients except for KLS patients who display memory deficit. Executive functions and higher-order cognition have been assessed in NT1 while they received little-to-no attention in the other CDH. NT1 patients display high performance in executive functions but exhibit a complex pattern of impairment in higher-order cognition, showing poor decision-making and impaired emotional processing. Moreover, NT1 patients show increased creative abilities. Assessing and monitoring cognitive impairments experienced by CDH patients will allow the design of personalized interventions, parallel to pharmacological treatment, aimed at improving daytime functioning and quality of life of these patients.

Association of Inattention, Hyperactivity, and Hypersomnolence in Two Clinic-Based Adult Cohorts

Objective: To assess the relationship between excessive daytime sleepiness (EDS), inattention, and hyperactivity/impulsivity in adults with ADHD and central hypersomnia. Method: Drug-free adult patients with ADHD (n = 100) or hypersomnia (n = 100) were evaluated using a structured clinical interview and self-report questionnaires on ADHD symptoms and EDS. Results: In all, 61% of patients with hypersomnia had clinically significant ADHD symptoms with 25% having an ADHD diagnosis (with both childhood and adulthood ADHD symptoms) and 36% ADHD-like symptoms, without history of childhood ADHD. EDS was reported in 47% of patients with ADHD, among whom 22% had a hypersomnolence disorder. Conclusion: We confirmed the high frequency of ADHD and ADHD-like symptoms in central hypersomnia, and of EDS and hypersomnolence in ADHD in adults. The nature of the link between EDS, inattention, and hyperactivity appears to be complex that may involve either a cause-effect relationship or intrinsic features of a similar neurodevelopmental dysfunction.

Reactive and predictive homeostasis: Roles of orexin/hypocretin neurons

Homeostasis is the maintenance of a healthy physiological equilibrium in a changing world. Reactive (feedback, counter-regulatory) and predictive (feedforward, anticipatory) homeostatic control strategies are both important for survival. For example, in energy homeostasis, the pancreas reacts to ingested glucose by releasing insulin, whereas the brain prepares the body for ingestion through anticipatory salivation based on food-associated cues. Reactive control is largely innate, whereas predictive control is often acquired or modified through associative learning, though some important predictive control strategies are innate, e.g. avoidance of fox scent in mice that never met a fox. Traditionally, the hypothalamus has been viewed as a reactive controller, sensing deviations from homeostasis to elicit counter-regulatory responses, while "higher" areas such as the cortex have been viewed as predictive controllers. However, experimental evidence argues against such neuroanatomical segregation: for example, receptors for internal homeostatic indicators are found throughout the brain, while key interoceptive hypothalamic cells also rapidly sense external cues. Here a model is proposed where the brain-wide-projecting, non-neuroendocrine, neurons of the hypothalamus, exemplified by orexin/hypocretin neurons, function as "brain government" systems that convert integrated internal and external information into reactive and predictive autonomic, cognitive, and behavioural adaptations that ensure homeostasis. Like regions of a country without a government, individual brain regions can function normally without hypothalamic guidance, but these functions are uncoordinated, producing mismatch between supply and demand of arousal, and derailing decision-making as seen in orexin-deficient narcolepsy. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.

How orexin signals bias action: Hypothalamic and accumbal circuits

Survival-maximizing, well-timed actions are a key responsibility of the brain. Hypothalamic neurons containing neurotransmitters orexins/hypocretins are important players in this process. Individuals without orexin neurons display inappropriately-timed transitions between arousal states, and other behavioural abnormalities including increased risk-taking. Deciphering neural circuits through which orexin neurons control brain states and behavior thus illuminates brain mechanisms of context-appropriate actions. This review outlines and puts into broader context recent examples of orexin circuit analyses in the lateral hypothalamus (LH) and the nucleus accumbens (NAc), two brain regions clasically implicated in context-appropriate actions. In the LH, orexin neurons excite GAD65-expressing neurons. The LH(GAD65) neuron excitation induces elevated locomotor activity, while inhibition of LH(GAD65) neuron natural activity depresses voluntary locomotion. The orexin → LH(GAD65) circuit may therefore assist in creating the drive to run. In the NAc shell region, orexin axons excite D2 neurons (dopamine-inhibited neurons expressing dopamine type-2 receptor). NAc(D2) cell activation increases risk-avoidance behaviors, while NAc(D2) cell inhibition reduces risk-avoidance. The excitatory orexin → NAc(D2) circuit may thus assist in reducing risk-taking, and oppose the inhibitory VTA(dopamine) → NAc(D2) circuit during computation of risk appetite. Neural computation in these local and long-range orexin circuits may thus assist in generating risk-avoiding locomotor responses to stressors known to activate orexin neurons, such as body energy depletion or potential external threats. A model is proposed where orexin-opposing, inhibitory inputs acting on the orexin target neurons may context-specifically channel orexin-induced brain excitation towards particular sets of actions.

Patterned feeding induces neuroendocrine, behavioral and genetic changes that promote palatable food intake

BACKGROUND

Selection of a healthy diet is the cornerstone for treating obesity and metabolic disease. Unfortunately, the majority of diets fail leading to weight regain and in some cases, pathological feeding behavior. We hypothesize that alternating bouts of caloric overconsumption and caloric restriction, behavioral manifestations of dieting induce neuroendocrine, behavioral and genetic changes that promote future bouts of palatable food intake.

METHODS

To test this hypothesis, we subjected male Long-Evans rats to a high-fat diet (HFD) feeding paradigm that induced a pattern of caloric overconsumption and caloric restriction. Under these conditions we measured operant responding for sucrose, pre-meal ghrelin secretion, the effects of peripheral ghrelin blockade on patterned feeding, HFD intake in an aversive environment and mRNA expression of the ghrelin receptor, orexin, orexin-1 and 2 receptors, and FTO in the medial prefrontal cortex, lateral hypothalamus and ventral tegmental area.

RESULTS

Rats subjected to this feeding regimen displayed increased ghrelin levels prior to HFD exposure and blockade of this response attenuated patterned feeding behavior. In addition, patterned feeding promoted enhanced motivation for sucrose, diminished extinction of this response and increased HFD intake in an aversive environment. The neuroendocrine and behavioral changes correlated with increased hypothalamic expression of the ghrelin receptor and FTO.

CONCLUSION

Collectively, these data indicate that patterns of feeding that include caloric overconsumption and caloric restriction induce neuroendocrine and neurobiological changes that signify an enhanced drive for palatable food.

Neural and neurochemical basis of reinforcement-guided decision making

Decision making is an adaptive behavior that takes into account several internal and external input variables and leads to the choice of a course of action over other available and often competing alternatives. While it has been studied in diverse fields ranging from mathematics, economics, ecology, and ethology to psychology and neuroscience, recent cross talk among perspectives from different fields has yielded novel descriptions of decision processes. Reinforcement-guided decision making models are based on economic and reinforcement learning theories, and their focus is on the maximization of acquired benefit over a defined period of time. Studies based on reinforcement-guided decision making have implicated a large network of neural circuits across the brain. This network includes a wide range of cortical (e.g., orbitofrontal cortex and anterior cingulate cortex) and subcortical (e.g., nucleus accumbens and subthalamic nucleus) brain areas and uses several neurotransmitter systems (e.g., dopaminergic and serotonergic systems) to communicate and process decision-related information. This review discusses distinct as well as overlapping contributions of these networks and neurotransmitter systems to the processing of decision making. We end the review by touching on neural circuitry and neuromodulatory regulation of exploratory decision making.

Treatment Options for Narcolepsy

Narcolepsy type 1 and narcolepsy type 2 are central disorders of hypersomnolence. Narcolepsy type 1 is characterized by excessive daytime sleepiness and cataplexy and is associated with hypocretin-1 deficiency. On the other hand, in narcolepsy type 2, cerebrospinal fluid hypocretin-1 levels are normal and cataplexy absent. Despite major advances in our understanding of narcolepsy mechanisms, its current management is only symptomatic. Treatment options may vary from a single drug that targets several symptoms, or multiple medications that each treats a specific symptom. In recent years, narcolepsy treatment has changed with the widespread use of modafinil/armodafinil for daytime sleepiness, antidepressants (selective serotonin and dual serotonin and noradrenalin reuptake inhibitors) for cataplexy, and sodium oxybate for both symptoms. Other psychostimulants can also be used, such as methylphenidate, pitolisant and rarely amphetamines, as third-line therapy. Importantly, clinically relevant subjective and objective measures of daytime sleepiness are required to monitor the treatment efficacy and to provide guidance on whether the treatment goals are met. Associated symptoms and comorbid conditions, such as hypnagogic/hypnopompic hallucinations, sleep paralysis, disturbed nighttime sleep, unpleasant dreams, REM- and non REM-related parasomnias, depressive symptoms, overweight/obesity, and obstructive sleep apnea, should also be taken into account and managed, if required. In the near future, the efficacy of new wake-promoting drugs, anticataplectic agents, hypocretin replacement therapy and immunotherapy at the early stages of the disease should also be evaluated.

Smoking, Alcohol, Drug Use, Abuse and Dependence in Narcolepsy and Idiopathic Hypersomnia: A Case-Control Study

STUDY OBJECTIVES

Basic experiments support the impact of hypocretin on hyperarousal and motivated state required for increasing drug craving. Our aim was to assess the frequencies of smoking, alcohol and drug use, abuse and dependence in narcolepsy type 1 (NT1, hypocretin-deficient), narcolepsy type 2 (NT2), idiopathic hypersomnia (IH) (non-hypocretin-deficient conditions), in comparison to controls. We hypothesized that NT1 patients would be less vulnerable to drug abuse and addiction compared to other hypersomniac patients and controls from general population.

METHODS

We performed a cross-sectional study in French reference centres for rare hypersomnia diseases and included 450 adult patients (median age 35 years; 41.3% men) with NT1 (n = 243), NT2 (n = 116), IH (n = 91), and 710 adult controls. All participants were evaluated for alcohol consumption, smoking habits, and substance (alcohol and illicit drug) abuse and dependence diagnosis during the past year using the Mini International Neuropsychiatric Interview.

RESULTS

An increased proportion of both tobacco and heavy tobacco smokers was found in NT1 compared to controls and other hypersomniacs, despite adjustments for potential confounders. We reported an increased regular and frequent alcohol drinking habit in NT1 versus controls but not compared to other hypersomniacs in adjusted models. In contrast, heavy drinkers were significantly reduced in NT1 versus controls but not compared to other hypersomniacs. The proportion of patients with excessive drug use (codeine, cocaine, and cannabis), substance dependence, or abuse was low in all subgroups, without significant differences between either hypersomnia disorder categories or compared with controls.

CONCLUSIONS

We first described a low frequency of illicit drug use, dependence, or abuse in patients with central hypersomnia, whether Hcrt-deficient or not, and whether drug-free or medicated, in the same range as in controls. Conversely, heavy drinkers were rare in NT1 compared to controls but not to other hypersomniacs, without any change in alcohol dependence or abuse frequency. Although disruption of hypocretin signaling in rodents reduces drug-seeking behaviors, our results do not support that hypocretin deficiency constitutes a protective factor against the development of drug addiction in humans.

Restless legs syndrome: update on pathogenesis

PURPOSE OF REVIEW

Much recent progress has been made in understanding restless legs syndrome (RLS), focusing mainly on genetic predisposition and dysregulation of iron metabolism and the dopaminergic system. We provide in this review an update of the most recent scientific advances on the pathophysiology of primary RLS.

RECENT FINDINGS

Genome-wide association studies identified six genetic variants including MEIS1 and BTBD9 with potential relationships with iron. Brain iron level is low in RLS and neuropathological studies have shown significant decreases in dopamine D2 receptors in the putamen that correlated with RLS severity, and increased tyrosine hydroxylase in the substantia nigra. An overly activated dopaminergic system was reported in both animal and cell models of iron insufficiency thus suggesting that in at least a subgroup of RLS patients altered iron metabolism plays a role in the disorder. Also, dysregulation of iron uptake and storage within brain microvessels was recently reported and might play a role in a subgroup of RLS patients.

SUMMARY

RLS is a genetically heterogeneous complex trait with high prevalence but large phenotype variability. Current theories of RLS pathophysiology emphasize brain iron deficiency with abnormal dopaminergic consequences, together with a strong underlying genetic background.

Reward-based behaviors and emotional processing in human with narcolepsy-cataplexy

Major advances in the past decade have led a better understanding of the pathophysiology of narcolepsy with cataplexy (NC) caused by the early loss of hypothalamic hypocretin neurons. Although a role for hypocretin in the regulation of sleep/wakefulness state is widely recognized, other functions, not necessarily related to arousal, have been identified. Hence, the hypocretin system enhances signaling in the mesolimbic pathways regulating reward processing, emotion and mood regulation, and addiction. Although studies on hypocretin-deficient mice have shown that hypocretin plays an essential role in reward-seeking, depression-like behavior and addiction, results in human narcolepsy remained subject to debate. Most of studies revealed that hypocretin-deficient narcolepsy patients either drug-free or medicated with psychostimulant had preferences toward risky choices in a decision-making task under ambiguity together with higher frequency of depressive symptoms and binge eating disorder compared to controls. However, human studies mostly reported the lack of association with pathological impulsivity and gambling, and substance and alcohol abuse in the context of narcolepsy-cataplexy. Prospective larger studies are required to confirm these findings in drug-free and medicated patients with narcolepsy. Inclusion of patients with other central hypersomnias without hypocretin deficiency will provide answer to the major question of the role of the hypocretin system in reward-based behaviors and emotional processing in humans.