Role of catecholamines in the modafinil and amphetamine induced wakefulness, a comparative pharmacological study in the cat

From past to future: 50 years of pharmacological interventions to treat narcolepsy

The history of narcolepsy research began with the pioneering work of Jean-Baptiste-Édouard Gélineau in the late 19th century. In the 1880s, Gélineau introduced the term "narcolepsy" to describe a condition characterized by sudden and uncontrollable episodes of sleep. His clinical descriptions laid the foundation for our understanding of this complex disorder. Over the last half-century, the pharmacological landscape for narcolepsy treatment has evolved remarkably, shifting from merely managing symptoms to increasingly targeting its underlying pathophysiology. By the 1930s, treatments such as ephedrine and amphetamine were introduced to alleviate excessive daytime sleepiness, marking significant advancements in narcolepsy management. These stimulants provided temporary relief, helping patients maintain wakefulness during the day. As research progressed, the focus shifted towards understanding the disorder's underlying mechanisms. The discovery of orexin (also known as hypocretin) in the late 1990s revolutionized the field. This breakthrough underscored the importance of orexin in regulating sleep-wake cycles and provided new targets for pharmacological intervention. Looking ahead, the future of narcolepsy pharmacotherapy is poised for further innovation. The ongoing exploration of orexin receptor agonists and the potential development of neuroprotective therapeutic targets underscore a promising horizon. Emerging research into the genetic and immunological underpinnings of narcolepsy opens new avenues for personalized medicine approaches and the identification of biomarkers for more precise treatment strategies. Additionally, the refinement of existing treatments through improved delivery systems and the investigation of combination therapies offer opportunities for enhanced efficacy and improved quality of life for patients with narcolepsy.

Sleep medicine, sleep research, and sleep education: a whole life devoted to sleep

This article describes my participation in sleep medicine, sleep research, and sleep education, mainly in Europe, between the years 1970 and 2000.

Atomoxetine promotes incentive value of modafinil and sensitizes exploratory behavior

Substance dependence is a disorder that alters the functioning of the nervous system due to frequent abuse of drugs. The role of dopamine in the addictive effect of psychostimulants is well known; however, the involvement of the noradrenergic system is still unclear and poorly understood, though drugs like cocaine and amphetamines are known to exert significant activity on this system. The drug modafinil (MOD) has no proven addictive effect. It promotes wakefulness by acting mainly on the dopaminergic system and, to a lesser degree, the noradrenergic (NOR) system. Atomoxetine (ATX) is a non-stimulant drug that acts only on the NOR system, enhancing its activity. The aims of the present study were to analyze the effect of co-activating the DA and NOR systems (with MOD and ATX, respectively) on motor activity and exploratory behavior, and to examine the possible emergence of rewarding properties of MOD and an MOD+ATX mixture. Male Wistar rats at postnatal day 60 were treated chronically (16 days) with either monotherapy with 2ATX, 4ATX, or 60MOD mg/kg, two combinations of these substances -60MOD + 2ATX and 60MOD + 4ATX- or a vehicle. The rats co-administered with 60MOD + 4ATX reduced the rearing behavior frequency induced by MOD, but this behavior was sensitized by self-administration of the MOD+ATX mixture after chronic treatment. The rats pre-treated with 60MOD + 4ATX showed higher self-administration of MOD and greater activity on an operant task to obtain the MOD+ATX mixture. In addition, the 60MOD, 2ATX, and 60MOD + 2ATX groups showed sensitization of exploratory behavior after ingesting the mixture. Results suggest that the noradrenergic system enhances the incentive value of MOD and a MOD+ATX mixture, while also playing an important role in the sensitization of exploratory behavior.

Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects

Modafinil is a nonamphetamine nootropic drug with an increasingly therapeutic interest due to its different sites of action and behavioral effects in comparison to cocaine or amphetamine. A review of modafinil (and of its prodrug adrafinil and its R-enantiomer armodafinil) chemical, pharmacokinetic, pharmacodynamic, toxicological, clinical and forensic aspects was performed, aiming to better understand possible health problems associated to its unconscious and unruled use. Modafinil is a racemate metabolized mainly in the liver into its inactive acid and sulfone metabolites, which undergo primarily renal excretion. Although not fully clarified, major effects seem to be associated to inhibition of dopamine reuptake and modulation of several other neurochemical pathways, namely noradrenergic, serotoninergic, orexinergic, histaminergic, glutamatergic and GABAergic. Due its wake-promoting effects, modafinil is used for the treatment of daily sleepiness associated to narcolepsy, obstructive sleep apnea and shift work sleep disorder. Its psychotropic and cognitive effects are also attractive in several other pathologies and conditions that affect sleep structure, induce fatigue and lethargy, and impair cognitive abilities. Additionally, in health subjects, including students, modafinil is being used off-label to overcome sleepiness, increase concentration and improve cognitive potential. The most common adverse effects associated to modafinil intake are headache, insomnia, anxiety, diarrhea, dry mouth and raise in blood pressure and heart rate. Infrequently, severe dermatologic effects in children, including maculopapular and morbilliform rash, erythema multiforme and Stevens-Johnson Syndrome have been reported. Intoxication and dependence associated to modafinil are uncommon. Further research on effects and health implications of modafinil and its analogs is steel needed to create evidence-based policies.

Genetic lesioning of histamine neurons increases sleep-wake fragmentation and reveals their contribution to modafinil-induced wakefulness

Acute chemogenetic inhibition of histamine (HA) neurons in adult mice induced nonrapid eye movement (NREM) sleep with an increased delta power. By contrast, selective genetic lesioning of HA neurons with caspase in adult mice exhibited a normal sleep-wake cycle overall, except at the diurnal start of the lights-off period, when they remained sleepier. The amount of time spent in NREM sleep and in the wake state in mice with lesioned HA neurons was unchanged over 24 hr, but the sleep-wake cycle was more fragmented. Both the delayed increase in wakefulness at the start of the night and the sleep-wake fragmentation are similar phenotypes to histidine decarboxylase knockout mice, which cannot synthesize HA. Chronic loss of HA neurons did not affect sleep homeostasis after sleep deprivation. However, the chronic loss of HA neurons or chemogenetic inhibition of HA neurons did notably reduce the ability of the wake-promoting compound modafinil to sustain wakefulness. Thus, part of modafinil's wake-promoting actions arise through the HA system.

Cortico-Amygdala-Striatal Activation by Modafinil/Flecainide Combination

Background

Modafinil, a nonamphetaminic wake-promoting compound, is prescribed as first line therapy in narcolepsy, an invalidating disorder characterized by excessive daytime sleepiness and cataplexy. Although its mode of action remains incompletely known, recent studies indicated that modafinil modulates astroglial connexin-based gap junctional communication as administration of a low dose of flecainide, an astroglial connexin inhibitor, enhanced the wake-promoting and procognitive activity of modafinil in rodents and healthy volunteers. The aim of this study is to investigate changes in glucose cerebral metabolism in rodents, induced by the combination of modafinil+flecainide low dose (called THN102).

Methods

The impact of THN102 on brain glucose metabolism was noninvasively investigated using 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography imaging in Sprague-Dawley male rats. Animals were injected with vehicle, flecainide, modafinil, or THN102 and further injected with 18F-2-fluoro-2-deoxy-D-glucose followed by 60-minute Positron Emission Tomography acquisition. 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography images were coregistered to a rat brain template and normalized from the total brain Positron Emission Tomography signal. Voxel-to-voxel analysis was performed using SPM8 software. Comparison of brain glucose metabolism between groups was then performed.

Results

THN102 significantly increased regional brain glucose metabolism as it resulted in large clusters of 18F-2-fluoro-2-deoxy-D-glucose uptake localized in the cortex, striatum, and amygdala compared with control or drugs administered alone. These regions, highly involved in the regulation of sleep-wake cycle, emotions, and cognitive functions were hence quantitatively modulated by THN102.

Conclusion

Data presented here provide the first evidence of a regional brain activation induced by THN102, currently being tested in a phase II clinical trial in narcoleptic patients.

Modafinil: its discovery, the early European and North American experience in the treatment of narcolepsy and idiopathic hypersomnia, and its subsequent use in other medical conditions

Adrafinil, a new molecule identified by a French drug company, L. Lafon Ltd, in 1974, was found to cause a significant dose-dependent increase in motor activity in mice, without exerting peripheral sympathomimetic effects. As early as 1977-78, Michel Jouvet prescribed adrafinil to narcoleptic patients, but without consistent results. Meanwhile the kinetics of adrafinil led to the identification of an active metabolite, modafinil. In 1983, Jouvet and Bastuji prescribed modafinil to narcoleptic and idiopathic hypersomnia patients and obtained a significant decrease of excessive daytime sleepiness and sleep attacks in a majority of patients. L. Lafon Ltd was initially not interested in developing this molecule for market however, thanks to Jouvet's insistance, it decided to start clinical trials in both healthy volunteers and narcoleptic patients as well as conduct animal studies. Results were excellent and led to the use of modafinil by the French army during the Gulf War in January-February 1991, as well as to the official registration of the drug in France in 1992. Subsequent multicenter controlled clinical trials in North America confirmed the findings in Europe. Modafinil was later used to treat sleepiness, somnolence and fatigue in a large number of medical conditions.

Modafinil enhances alerting-related brain activity in attention networks

RATIONALE

Modafinil is a wake-promoting agent and has been reported to be effective in improving attention in patients with attentional disturbance. However, neural substrates underlying the modafinil effects on attention are not fully understood.

OBJECTIVES

We employed a functional magnetic resonance imaging (fMRI) study with the attention network test (ANT) task in healthy adults and examined which networks of attention are mainly affected by modafinil and which neural substrates are responsible for the drug effects.

METHODS

We used a randomized placebo-controlled within-subjects cross-over design. Twenty-three healthy adults participated in two series of an fMRI study, taking either a placebo or modafinil. The participants performed the ANT task, which is designed to measure three distinct attentional networks, alerting, orienting, and executive control, during the fMRI scanning. The effects of modafinil on behavioral performance and regional brain activity were analyzed.

RESULTS

We found that modafinil enhanced alerting performance and showed greater alerting network activity in the left middle and inferior occipital gyri as compared with the placebo. The brain activations in the occipital regions were positively correlated with alerting performance.

CONCLUSIONS

Modafinil enhanced alerting performance and increased activation in the occipital lobe in the alerting network possibly relevant to noradrenergic activity during the ANT task. The present study may provide a rationale for the treatment of patients with distinct symptoms of impaired attention.

Dorsal Raphe Dopamine Neurons Modulate Arousal and Promote Wakefulness by Salient Stimuli

Ventral midbrain dopamine (DA) is unambiguously involved in motivation and behavioral arousal, yet the contributions of other DA populations to these processes are poorly understood. Here, we demonstrate that the dorsal raphe nucleus DA neurons are critical modulators of behavioral arousal and sleep-wake patterning. Using simultaneous fiber photometry and polysomnography, we observed time-delineated dorsal raphe nucleus dopaminergic (DRN^DA) activity upon exposure to arousal-evoking salient cues, irrespective of their hedonic valence. We also observed broader fluctuations of DRN^DA activity across sleep-wake cycles with highest activity during wakefulness. Both endogenous DRN^DA activity and optogenetically driven DRN^DA activity were associated with waking from sleep, with DA signal strength predictive of wake duration. Conversely, chemogenetic inhibition opposed wakefulness and promoted NREM sleep, even in the face of salient stimuli. Therefore, the DRN^DA population is a critical contributor to wake-promoting pathways and is capable of modulating sleep-wake states according to the outside environment, wherein the perception of salient stimuli prompts vigilance and arousal.

Schizophrenia: the role of sleep and circadian rhythms in regulating dopamine and psychosis

Schizophrenia has long been associated with abnormalities in circadian rhythms and sleep. Up until now, there have been no thorough reviews of the potential mechanisms behind the myriad of circadian and sleep abnormalities observed in schizophrenia and psychosis. We present evidence of sleep playing an important role in psychosis predominantly mediated by dopaminergic pathways. A synthesis of both human and animal experimental work suggests that the interplay between sleep and dopamine is important in the generation and maintenance of psychosis. In particular, both animal and human data point to sleep disruption increasing dopamine release and sensitivity. Furthermore, elevated dopamine levels disrupt sleep and circadian rhythms. The synthesis of knowledge suggests that circadian rhythms, dopamine dysregulation, and psychosis are intricately linked. This suggests that treatment of circadian disturbance may be a useful target in improving the lives and symptoms of patients with schizophrenia.

Impact of Astroglial Connexins on Modafinil Pharmacological Properties

STUDY OBJECTIVES

Modafinil is a non-amphetaminic wake-promoting compound used as therapy against sleepiness and narcolepsy. Its mode of action is complex, but modafinil has been recently proposed to act as a cellular-coupling enhancer in glial cells, through modulation of gap junctions constituted by connexins. The present study investigated in mice the impact of connexins on the effects of modafinil using connexin inhibitors.

METHODS

Modafinil was administered alone or combined with inhibitors of astrocyte connexin, meclofenamic acid, or flecainide, respectively, acting on Cx30 and Cx43. Sleep-wake states were monitored in wild-type and narcoleptic orexin knockout mice. A spontaneous alternation task was used to evaluate working memory in wild-type mice. The effects of the compounds on astroglial intercellular coupling were determined using dye transfer in acute cortical slices.

RESULTS

Meclofenamic acid had little modulation on the effects of modafinil, but flecainide enhanced the wake-promoting and pro-cognitive effects of modafinil. Co-administration of modafinil/flecainide resulted in a marked decrease in the number and duration of direct transitions to rapid eye movement sleep, which are characteristic of narcoleptic episodes in orexin knockout mice. Furthermore, modafinil enhanced the connexin-mediated astroglial cell coupling, whereas flecainide reduced it. Finally, this modafinil-induced effect was reversed by co-administration with flecainide.

CONCLUSIONS

Our study indicates that flecainide impacts the pharmacological effects of modafinil, likely through the normalization of Cx30-dependent gap junctional coupling in astroglial networks. The enhancement of the wake-promoting, behavioral, and cognitive outcomes of modafinil demonstrated here with flecainide would open new perspectives in the management of sleep disorders such as narcolepsy.

COMMENTARY

A commentary on this article appears in this issue on page 1175.

Evaluation of the Effect of Modafinil on Cognitive Functions in Patients with Idiopathic Hypersomnia with P300

Background

Modafinil is a well-tolerated psychostimulant drug with low addictive potential that is used to treat patients with narcolepsy and other excessive sleepiness. Whereas favorable effects of modafinil on cognitive functions have been shown in a large number of studies, there are very few reports presenting the effects of modafinil electrophysiologically. The aim of this study was to investigate the effects of modafinil on auditory P300 latency and amplitude electrophysiologically.

Material/Methods

Eighteen patients (age range: 16–48 years) with a diagnosis of idiopathic hypersomnia (IH) were included in the present study. As a standard treatment, 200 mg/day modafinil was administered to each patient. The P300 auditory test was performed for each patient before and at the end of 1 week of modafinil treatment.

Results

After 1 week of modafinil treatment, mean P300 latencies (at all electrode sites) were significantly lower than the latencies before the treatment (P values for Fz, Cz and Pz recording sites were 0.039, 0.002, and 0.004, respectively). An increase in the P300 amplitudes was detected only at the Fz recording site, but not at Cz or Pz recording sites (P values for Fz, Cz, and Pz recording sites were 0.014, 0.100, and 0.05, respectively).

Conclusions

One week of modafinil treatment improved the cognitive performance, alertness, and executive functions in IH patients. Our electrophysiologically obtained findings provide further confirmation for previous reports in which modafinil has been shown to exert favorable effects on cognitive performance, alertness, and executive functions.

Facilitation of spatial working memory performance following intra-prefrontal cortical administration of the adrenergic alpha1 agonist phenylephrine

RATIONALE

Spatial working memory is dependent on the appropriate functioning of the prefrontal cortex (PFC). PFC activity can be modulated by noradrenaline (NA) released by afferent projections from the locus coeruleus. The coreuleo-cortical NA system could therefore be a target for cognitive enhancers of spatial working memory. Of the three classes of NA receptor potentially involved, the α2 and α1 classes seem most significant, though agents targeting these receptors have yielded mixed results. This may be partially due to the use of behavioural assays that do not translate effectively from the laboratory to the clinical setting. Use of a paradigm with improved translational potential may be essential to resolve these discrepancies.

OBJECTIVES

The objective of this study was to assess the effects of PFC-infused α2 and α1 adrenergic receptor agonists on spatial working memory performance in the touchscreen continuous trial-unique non-matching to location (cTUNL) task in rats.

METHODS

Young male rats were trained in the cTUNL paradigm. Cannulation of the mPFC allowed direct administration of GABA agonists for task validation, and phenylephrine and guanfacine to determine the effects of adrenergic agonists on task performance.

RESULTS

Infusion of muscimol and baclofen resulted in a delay-dependent impairment. Administration of the α2 agonist guanfacine had no effect, whilst infusion of the α1 agonist phenylephrine significantly improved working memory performance.

CONCLUSIONS

Spatial working memory as measured in the rat cTUNL task is dependent on the mPFC. Enhancement of noradrenergic signalling enhanced performance in this paradigm, suggesting a significant role for the α1 receptor in this facilitation.

Duration of activity and mode of action of modafinil: Studies on sleep and wakefulness in humans

The duration of activity of modafinil was investigated in healthy male volunteers in two double-blind crossover studies. Mode of action was explored using a statistical model concerned with the relationship between total sleep duration and that of rapid eye movement (REM) sleep. Nocturnal sleep (23:00-07:00) followed by next-day performance (09:00-17:00) was studied in 12 subjects administered 100, 200, 300 mg modafinil and placebo, 0.5 h before bedtime. Performance overnight (19:00-08:45) followed by sleep (09:15-15:15) was studied in nine subjects administered 100, 200, 300, 400 mg modafinil, 300 mg caffeine and placebo at 22:15. Modafinil dose-dependently reduced sleep duration (nocturnal: 200 mg, p<0.05; 300 mg, p<0.001; morning: 300 and 400 mg, p<0.05) and REM sleep (nocturnal: 300 mg; morning: 400 mg; p<0.05). The statistical model revealed that reduced REM sleep was due to alerting activity, with no evidence of direct suppression of REM sleep, suggesting dopaminergic activity. Enhanced performance with modafinil during overnight work varied with dose (200 mg>100 mg; 300, 400 mg>200, 100 mg, caffeine). However, in the study of next-day performance, the enhancement was attenuated at the highest dose (300 mg) by the greater disturbance of prior sleep. These findings indicate that modafinil has a long duration of action, with alerting properties arising predominantly from dopaminergic activity.

Armodafinil-induced wakefulness in animals with ventrolateral preoptic lesions

Armodafinil is the pharmacologically active R-enantiomer of modafinil, a widely prescribed wake-promoting agent used to treat several sleep-related disorders including excessive daytime sleepiness associated with narcolepsy, shift work sleep disorder, and obstructive sleep apnea/hypopnea syndrome. Remarkably, however, the neuronal circuitry through which modafinil exerts its wake-promoting effects remains unresolved. In the present study, we sought to determine if the wake-promoting effects of armodafinil are mediated, at least in part, by inhibiting the sleep-promoting neurons of the ventrolateral preoptic (VLPO) nucleus. To do so, we measured changes in waking following intraperitoneal administration of armodafinil (200 mg/kg) or the psychostimulant methamphetamine (1 mg/kg) in rats with cell-body specific lesion of the VLPO. Rats with histologically confirmed lesions of the VLPO demonstrated a sustained increase in wakefulness at baseline, but the increase in wakefulness following administration of both armodafinil and methamphetamine was similar to that of intact animals. These data suggest that armodafinil increases wakefulness by mechanisms that extend beyond inhibition of VLPO neurons.

Modafinil as a catecholaminergic agent: empirical evidence and unanswered questions

Modafinil, in its two clinical formulations (Provigil^® and Nuvigil^®), is a widely prescribed wake-promoting therapeutic agent. It binds competitively to the cell-membrane dopamine (DA) transporter and is dependent on catecholaminergic (dopaminergic and adrenergic) signaling for its wake-promoting effects. The clinical spectrum of effects for modafinil is distinct from the effects seen with other catecholaminergic agents. Relative to other commonly used agents that act through catecholaminergic mechanisms, modafinil has a relatively low abuse potential, produces wakefulness with an attenuated compensatory sleep recovery thereafter, and does not ameliorate cataplexy in narcolepsy. These clinically relevant phenomenological differences between modafinil and agents such as amphetamines and cocaine do not eliminate catecholaminergic effects as a possible mediator of its wake-promoting action; they merely reflect its unique pharmacological profile. Modafinil is an exceptionally weak, but apparently very selective, DA transporter inhibitor. The pharmacodynamic response to modafinil, as measured by DA levels in brain microdialyzate, is protracted relative to other agents that act via catecholaminergic mechanisms. The conformational constraints on the interaction of modafinil with the DA transporter – and probably, as a consequence, its effects on trace amine receptor signaling in the catecholaminergic cell – are unique among catecholaminergic agents. These unique pharmacological properties of modafinil should be considered both in seeking to thoroughly understand its putatively elusive mechanism of action and in the design of novel therapeutic agents.

The neurobiology of modafinil as an enhancer of cognitive performance and a potential treatment for substance use disorders

RATIONALE AND OBJECTIVES

Modafinil (MOD) and its R-enantiomer (R-MOD) are approved medications for narcolepsy and other sleep disorders. They have also been used, off-label, as cognitive enhancers in populations of patients with mental disorders, including substance abusers that demonstrate impaired cognitive function. A debated nonmedical use of MOD in healthy individuals to improve intellectual performance is raising questions about its potential abuse liability in this population.

RESULTS AND CONCLUSIONS

MOD has low micromolar affinity for the dopamine transporter (DAT). Inhibition of dopamine (DA) reuptake via the DAT explains the enhancement of DA levels in several brain areas, an effect shared with psychostimulants like cocaine, methylphenidate, and the amphetamines. However, its neurochemical effects and anatomical pattern of brain area activation differ from typical psychostimulants and are consistent with its beneficial effects on cognitive performance processes such as attention, learning, and memory. At variance with typical psychostimulants, MOD shows very low, if any, abuse liability, in spite of its use as a cognitive enhancer by otherwise healthy individuals. Finally, recent clinical studies have focused on the potential use of MOD as a medication for treatment of drug abuse, but have not shown consistent outcomes. However, positive trends in several result measures suggest that medications that improve cognitive function, like MOD or R-MOD, may be beneficial for the treatment of substance use disorders in certain patient populations.

Efficacy and safety of adjunctive modafinil treatment on residual excessive daytime sleepiness among nasal continuous positive airway pressure-treated japanese patients with obstructive sleep apnea syndrome: a double-blind placebo-controlled study

STUDY OBJECTIVES

This double-blind study evaluated the efficacy and safety of modafinil for treating excessive daytime sleepiness in Japanese patients with obstructive sleep apnea syndrome (OSAS).

METHODS

Patients with residual excessive sleepiness (Epworth Sleepiness Scale [ESS] ≥ 11) on optimal nasal continuous positive airway pressure (nCPAP) therapy (apnea-hypopnea index ≤ 10) were randomized to either 200 mg modafinil (n = 52) or placebo (n = 62) once daily for 4 weeks. Outcomes included baseline-week 4 changes in ESS total score, sleep latency on maintenance of wakefulness test (SL-MWT), nocturnal polysomnography, Pittsburgh Sleep Quality Index (PSQI), and safety.

RESULTS

All 114 randomized patients completed the study. Mean change in ESS total score (-6.6 vs -2.4, p < 0.001) and SL-MWT (+2.8 vs -0.4 minutes, p = 0.009) were significantly greater with modafinil than with placebo. ESS total score decreased from > 11 to < 11 at the final assessment in 69.2% of modafinil-treated patients and 30.6% of placebo-treated patients (p < 0.001). Corresponding rates at week 1 were 57.7% and 33.9% (p = 0.014). Changes in nocturnal polysomnography, PSQI, and apnea-hypopnea index from baseline to the final assessment were similar in both groups. Adverse drug reactions occurred in 36.5% and 22.6% of patients in the modafinil and placebo groups, respectively (p = 0.146).

CONCLUSIONS

Once-daily modafinil was effective and well tolerated for managing residual daytime sleepiness in Japanese OSAS patients with residual excessive daytime sleepiness on optimal nCPAP therapy.

Combined effects of modafinil and d-amphetamine in male Sprague-Dawley rats trained to discriminate d-amphetamine

Modafinil is a novel wake-promoting drug with FDA approval for the treatment of sleep-related disorders that has recently been investigated as a potential agonist replacement therapy for psychostimulant dependence. Previous research in animals and humans indicates modafinil has a lower abuse liability than traditional psychostimulants, although few studies have carefully assessed modafinil's stimulus properties in combination with other psychostimulants. The current study trained male Sprague-Dawley rats to discriminate subcutaneous injections of 0.3 mg/kg (n=8) or 1.0 mg/kg d-amphetamine (n=8) from saline under an FR 20 schedule of food reinforcement and substitution tests were administered with d-amphetamine (0.03-1.0 mg/kg, s.c.), modafinil (32-256 mg/kg, i.g.), and a low modafinil dose (32 mg/kg, i.g.) in combination with d-amphetamine (0.03-1.0 mg/kg, s.c.) to determine if these drugs have additive effects. The selective D2 dopamine agonist, PNU-91356A, was also tested as a positive control and ethanol and morphine were tested as negative controls. Results indicate that modafinil produced dose-dependent and statistically significant d-amphetamine-lever responding in both groups and nearly complete substitution in animals trained to discriminate 1.0 mg/kg d-amphetamine. Modafinil pretreatment slightly increased the discrimination of low d-amphetamine doses in animals trained to discriminate 0.3 mg/kg d-amphetamine. These results support previous findings that modafinil and d-amphetamine may have additive effects. In consideration of recent interests in modafinil as an agonist treatment for psychostimulant dependence, additional preclinical investigations utilizing other methodologies to examine modafinil in combination with other stimulants, such as behavioral sensitization paradigms or drug self-administration, may be of interest.

Use of adjunctive stimulants in adult bipolar depression

Bipolar depression represents a high priority research field, due to its pervasiveness, and high economic and personal (suicidality, impaired function, quality of life) costs, and the limited evidence base to inform therapeutics. Mood stabilizers and second-generation antipsychotics for bipolar depression are commonly only partially effective, and their side-effects may overlap with depressive symptoms such as hypersomnia, daytime drowsiness, fatigue, psychomotor retardation, and weight gain. Moreover, the use of antidepressants in bipolar depression is controversial due to concerns regarding the risks of inefficacy or switching to mood elevation. Stimulants and related compounds such as modafinil and armodafinil have on occasion been used as adjuncts in bipolar depressed patients with encouraging results, but their use is limited by the paucity of systematic evidence of efficacy and safety. The present review aims to provide an updated perspective on the use of stimulants and stimulant-like medications in adult bipolar depression, considering not only recent randomized controlled trials, but also open naturalistic studies, in order to clarify the strengths and limitations of using these agents.

Excessive daytime sleepiness and narcolepsy--an approach to investigation and management

Excessive daytime sleepiness is a common presentation to physicians both in general practice and hospital settings. In this review, we provide an update on the latest theories on the pathogenesis of the condition, and discuss the approach to investigation of the sleepy patient, with particular reference to narcolepsy. Recommended therapy is reviewed for both narcolepsy and cataplexy, to provide physicians with an important reference on the investigation and management of these troubling conditions.

Current and future therapeutic approaches in narcolepsy

Narcolepsy with cataplexy (NC) is a disabling orphan sleep disorder characterized by excessive daytime sleepiness, cataplexy and other dissociated manifestations of rapid eye movement sleep (hypnagogic hallucinations and sleep paralysis), as well as frequent movement and awakening during night-time sleep. In this article, we will describe the main symptoms and the current and future treatments of NC. Pathophysiological studies have shown that NC is caused by the early loss of neurons in the hypothalamus that produce hypocretin/orexin, a wakefulness-associated neurotransmitter present in cerebrospinal fluid. The cause of neural loss could be autoimmune since most patients have the human leukocyte antigen DQB1*0602 allele that predisposes individuals to NC. The treatment of narcolepsy has evolved over the past few years with the widespread use of modafinil for daytime sleepiness, antidepressants for cataplexy and γ-hydroxybutyrate (sodium oxybate) for both symptoms. Potential development of new wake-promoting drugs, anticataplectic medications, slow-wave sleep-enhancing treatments, hypocretin-replacement therapy and immunotherapy at early stages of the disease needs to be evaluated in the near future.

To what extent do neurobiological sleep-waking processes support psychoanalysis?

Sigmund Freud's thesis was that there is a censorship during waking that prevents memory of events, drives, wishes, and feelings from entering the consciousness because they would induce anxiety due to their emotional or ethical unacceptability. During dreaming, because the efficiency of censorship is decreased, latent thought contents can, after dream-work involving condensation and displacement, enter the dreamer's consciousness under the figurative form of manifest content. The quasi-closed dogma of psychoanalytic theory as related to unconscious processes is beginning to find neurobiological confirmation during waking. Indeed, there are active processes that suppress (repress) unwanted memories from entering consciousness. In contrast, it is more difficult to find neurobiological evidence supporting an organized dream-work that would induce meaningful symbolic content, since dream mentation most often only shows psychotic-like activities.

Infusion of modafinil into anterior hypothalamus or pedunculopontine tegmental nucleus at different time-points enhances waking and blocks the expression of recovery sleep in rats after sleep deprivation

Clinical studies have indicated that the primary pharmacological activity of modafinil (MOD) is inducing wakefulness; however, the brain targets that underlie its wake-promoting activity have not been described. In the present study, we show that MOD injected into sleep-wake related brain areas promoted alertness. If administered (10, 20, or 30 μg/1 μL) into either anterior hypothalamus (AH) or pedunculopontine tegmental nucleus (PPTg) at 08:00, 12:00 or 16:00 h, MOD enhanced wakefulness whereas diminished slow wave sleep as well as rapid eye movement sleep. In addition, microinjection of MOD (10, 20, or 30 μg/1 μL) either into AH or PPTg after total sleep deprivation prevented the sleep rebound. Taken together, these observations suggest that AH and PPTg play a key role in the wake-inducing effects of MOD and encourage further experimentation to draw a possible mechanism of action.

Effects of modafinil on emotional processing in first episode psychosis

BACKGROUND

Emotional impairments are important determinants of functional outcome in psychosis, and current treatments are not particularly effective. Modafinil is a wake-promoting drug that has been shown to improve emotion discrimination in healthy individuals and attention and executive function in schizophrenia. We aimed to establish whether modafinil might have a role in the adjuvant treatment of emotional impairments in the first episode of psychosis, when therapeutic endeavor is arguably most vital.

METHODS

Forty patients with a first episode of psychosis participated in a randomized, double-blind, placebo-controlled crossover design study testing the effects of a single dose of 200 mg modafinil on neuropsychological performance. Emotional functions were evaluated with the emotional face recognition test, the affective go-no go task, and the reward and punishment learning test. Visual analogue scales were used throughout the study to assess subjective mood changes.

RESULTS

Modafinil significantly improved the recognition of sad facial expressions (z = 2.98, p = .003). In contrast, there was no effect of modafinil on subjective mood ratings, on tasks measuring emotional sensitivity to reward or punishment, or on interference of emotional valence on cognitive function, as measured by the affective go-no go task.

CONCLUSIONS

Modafinil improves the analysis of emotional face expressions. This might enhance social function in people with a first episode of psychosis.

The waking brain: an update

Wakefulness and consciousness depend on perturbation of the cortical soliloquy. Ascending activation of the cerebral cortex is characteristic for both waking and paradoxical (REM) sleep. These evolutionary conserved activating systems build a network in the brainstem, midbrain, and diencephalon that contains the neurotransmitters and neuromodulators glutamate, histamine, acetylcholine, the catecholamines, serotonin, and some neuropeptides orchestrating the different behavioral states. Inhibition of these waking systems by GABAergic neurons allows sleep. Over the past decades, a prominent role became evident for the histaminergic and the orexinergic neurons as a hypothalamic waking center.

Central serous chorioretinopathy associated with narcolepsy

PURPOSE

The purpose of this study was to describe a case of central serous chorioretinopathy (CSC) associated with narcolepsy.

METHODS

Case report.

RESULTS

A 34-year-old man was followed for persistent CSC in his left eye for more than 11 months. He did not have any known risk factors for CSC, including obstructive sleep apnea. However, he experienced disrupted sleep because of narcolepsy, which was inadequately treated. After 2 weeks of adequate treatment for his narcolepsy, fundus examination and optic coherence tomography demonstrated complete resolution of his CSC.

CONCLUSION

As this case report suggests, overactivation of the hypothalamic-pituitary-adrenal axis and sympathetic nervous system, seen with disrupted and poor quality sleep, may contribute to the development of CSC. Risk factors for CSC should include sleep disorders that can lead to chronic sleep deprivation.

Effects of modafinil and prazosin on cognitive and physiological functions in healthy volunteers

Previous research has demonstrated cognitive-enhancing effects of modafinil in humans and generated evidence for its therapeutic potential in psychiatric disorders. The neurochemical basis of these effects remains unresolved although a role for α1-adrenoceptors has been hypothesised. In this within-subject, double-blind, placebo-controlled study, 12 healthy male adults received modafinil (300 mg), the α1-adrenoceptor antagonist prazosin (3 mg), both together and placebo on separate occasions at least 5 days apart. Cognitive effects were assessed using a well-validated testing battery focusing on executive and working memory functions. Blood pressure, heart rate and salivary α-amylase (sAA) were measured at hourly intervals. Cognitive effects of modafinil and prazosin were identified at the difficult levels of the One-Touch Stockings of Cambridge (OTSOC) planning task. Prazosin antagonized the error-reducing effect of modafinil when the agents were given together. In contrast, the combined agents acted synergistically to increase time taken to complete OTSOC problems compared with placebo. The tachycardic and sAA-elevating effects of prazosin were also potentiated by concurrent modafinil administration. The current data suggest that the cognitive effects of modafinil on performance accuracy and latency are dissociable in terms of their neurochemical mechanisms. Our findings support the hypothesised involvement of α1-adrenoceptors in some of the cognitive-enhancing effects of modafinil and warrant further investigation.

Agonist-like pharmacotherapy for stimulant dependence: preclinical, human laboratory, and clinical studies

A variety of natural and synthetic agents have long been used for stimulant properties, with nontherapeutic use producing multiple waves of stimulant abuse and dependence. The multitude of effects of stimulants exist on continua, and accordingly, here we characterize stimulant abuse/dependence and candidate pharmacotherapies in this manner. Behavioral therapy and medications have been investigated for treatment of stimulant abuse/dependence. Effectiveness of some behavioral interventions has been demonstrated. Most medications studied have been found to lack efficacy. However, an expanding literature supports use of agonist-like medications to treat stimulant abuse/dependence, a strategy effective for nicotine and opiate dependence. The agonist-like conceptualization for stimulant dependence posits that medications with properties similar to that of the abused drug, but possessing lesser abuse liability, will normalize neurochemistry and stabilize behavior, thus reducing drug use. Data suggest use of a range of medications, from l-dopa/carbidopa to amphetamine preparations, depending on the severity of use. This report reviews preclinical, human laboratory, and clinical trial data supporting the agonist-like approach, including risks and benefits. Future directions for development of agonist-like medications are also discussed.

The roles of dopamine transport inhibition and dopamine release facilitation in wake enhancement and rebound hypersomnolence induced by dopaminergic agents

STUDY OBJECTIVE

Rebound hypersomnolence (RHS: increased sleep following increased wake) is a limiting side-effect of many wake-promoting agents. In particular, RHS in the first few hours following wake appears to be associated with dopamine (DA)-releasing agents, e.g., amphetamine, but whether it can also be produced by DA transporter (DAT) inhibition alone is unknown. In these studies, DA-releasing and DAT-inhibiting agents and their interaction were systematically examined for their ability to increase wake and induce RHS.

DESIGN

Chronically implanted rats were evaluated in a blinded, pseudo-randomized design.

PARTICIPANTS

237 rats were used in these studies with 1 week between repeat tests.

INTERVENTIONS

Animals were habituated overnight and dosed the next day, 5 h after lights on, with test agents.

MEASUREMENTS AND RESULTS

Sleep/wake activityand RHS were evaluated using EEG/EMG recording up to 22 h post dosing. In vitro dopamine release was evaluated in rat synaptosomes. At doses that produced equal increases in wake, DA-releasing (amphetamine, methamphetamine, phentermine) and several DAT-inhibiting agents (cocaine, bupropion, and methylphenidate) produced RHS during the first few hours after the onset of sleep recovery. However, other DAT-inhibiting agents (mazindol, nomifensine, GBR-12909, and GBR-12935) did not produce RHS. Combination treatment with amphetamine and nomifensine produced waking activity greater than the sum of their individual activities alone while ameliorating the amphetamine-like RHS. In rat synaptosomes, nomifensine reduced the potency of amphetamine to induce DA release approximately 270-fold, potentially explaining its action in ameliorating amphetamine-induced RHS.

CONCLUSIONS

All DA releasing agents tested, and some DAT-inhibiting agents, produced RHS at equal wake-promoting doses. Thus amphetamine-like DA release appears sufficient for inducing RHS, but additional properties (pharmacologic and/or pharmacokinetic) evidently underlie RHS of other DAT inhibitors. Enhancing wake while mitigating RHS can be achieved by combining DAT-inhibiting and DA-releasing agents.

Good night and good luck: norepinephrine in sleep pharmacology

Sleep is a crucial biological process that is regulated through complex interactions between multiple brain regions and neuromodulators. As sleep disorders can have deleterious impacts on health and quality of life, a wide variety of pharmacotherapies have been developed to treat conditions of excessive wakefulness and excessive sleepiness. The neurotransmitter norepinephrine (NE), through its involvement in the ascending arousal system, impacts the efficacy of many wake- and sleep-promoting medications. Wake-promoting drugs such as amphetamine and modafinil increase extracellular levels of NE, enhancing transmission along the wake-promoting pathway. GABAergic sleep-promoting medications like benzodiazepines and benzodiazepine-like drugs that act more specifically on benzodiazepine receptors increase the activity of GABA, which inhibits NE transmission and the wake-promoting pathway. Melatonin and related compounds increase sleep by suppressing the activity of the neurons in the brain's circadian clock, and NE influences the synthesis of melatonin. Antihistamines block the wake-promoting effects of histamine, which shares reciprocal signaling with NE. Many antidepressants that affect the signaling of NE are also used for treatment of insomnia. Finally, adrenergic receptor antagonists that are used to treat cardiovascular disorders have considerable sedative effects. Therefore, NE, long known for its role in maintaining general arousal, is also a crucial player in sleep pharmacology. The purpose of this review is to consider the role of NE in the actions of wake- and sleep-promoting drugs within the framework of the brain arousal systems.

Narcolepsy and depression and the neurobiology of gammahydroxybutyrate

A voluminous literature describes the relationship between disturbed sleep and depression. The breakdown of sleep is one of the cardinal features of depression and often also heralds its onset. Frequent arousals, periods of wakefulness and a short sleep onset REM latency are typical polysomnographic features of depression. The short latency to REM sleep has been attributed to the combination of a monoaminergic deficiency and cholinergic supersensitivity and these irregularities have been proposed to form the biological basis of the disorder. A similar imbalance between monoaminergic and cholinergic neurotransmission has been found in narcolepsy, a condition in which frequent awakenings, periods of wakefulness and short sleep onset REM latencies are also characteristic findings during sleep. In many cases of narcolepsy, this imbalance appears to result from a deficiency of hypocretin but once established, whether in depression or narcolepsy, this disequilibrium sets the stage for the dissociation or premature appearance of REM sleep and for the dissociation of the motor inhibitory component of REM sleep or cataplexy. In the presence of this monoaminergic/cholinergic imbalance, gammahydroxybutyrate (GHB) may acutely further reduce the latency of REM sleep and induce cataplexy, in both patients with narcolepsy or depression. On the other hand, the repeated nocturnal application of GHB in patients with narcolepsy improves the continuity of sleep, prolongs the latency to REM sleep and prevents cataplexy. Evidence to date suggests that GHB may restore the normal balance between monoaminergic and cholinergic neurotransmission. As such, the repeated use of GHB at night and the stabilization of sleep over time makes GHB an effective treatment for narcolepsy and a potentially effective treatment for depression.