Modafinil: a review of neurochemical actions and effects on cognition

Chronic modafinil effects on drug-seeking following methamphetamine self-administration in rats

Acute administration of the cognitive enhancing drug, modafinil (Provigil®), reduces methamphetamine (Meth) seeking following withdrawal from daily self-administration. However, the more clinically relevant effects of modafinil on Meth-seeking after chronic treatment have not been explored. Here, we determined the impact of modafinil on Meth-seeking after chronic daily treatment during extinction or abstinence following Meth self-administration. Rats self-administered intravenous Meth during daily 2-h sessions for 14 d, followed by extinction sessions or abstinence. During this period, rats received daily injections of vehicle, 30, or 100 mg/kg modafinil and were then tested for Meth-seeking via cue, Meth-primed, and context-induced reinstatement at early and late withdrawal time-points. We found that chronic modafinil attenuated relapse to a Meth-paired context, decreased conditioned cue-induced and Meth-primed reinstatement, and resulted in enduring reductions in Meth-seeking even after discontinuation of treatment. Additionally, we determined that only a very high dose of modafinil (300 mg/kg) during maintenance of self-administration had an impact on Meth intake. These results validate and extend clinical and preclinical findings that modafinil may be a viable treatment option for Meth addiction.

Effects of modafinil on non-verbal cognition, task enjoyment and creative thinking in healthy volunteers

Background

Modafinil, a putative cognitive enhancing drug, has previously been shown to improve performance of healthy volunteers as well as patients with attention deficit disorder and schizophrenia, mainly in tests of executive functions. The aim of this study was to investigate the effects of modafinil on non-verbal cognitive functions in healthy volunteers, with a particular focus on variations of cognitive load, measures of motivational factors and the effects on creative problem-solving.

Methods

A double-blind placebo-controlled parallel design study evaluated the effect of 200 mg of modafinil (N = 32) or placebo (N = 32) in non-sleep deprived healthy volunteers. Non-verbal tests of divergent and convergent thinking were used to measure creativity. A new measure of task motivation was used, together with more levels of difficulty on neuropsychological tests from the CANTAB battery.

Results

Improvements under modafinil were seen on spatial working memory, planning and decision making at the most difficult levels, as well as visual pattern recognition memory following delay. Subjective ratings of enjoyment of task performance were significantly greater under modafinil compared with placebo, but mood ratings overall were not affected. The effects of modafinil on creativity were inconsistent and did not reach statistical significance.

Conclusions

Modafinil reliably enhanced task enjoyment and performance on several cognitive tests of planning and working memory, but did not improve paired associates learning. The findings confirm that modafinil can enhance aspects of highly demanding cognitive performance in non-sleep deprived individuals.

This article is part of a Special Issue entitled ‘Cognitive Enhancers’.

Atomoxetine modulates spontaneous and sensory-evoked discharge of locus coeruleus noradrenergic neurons

Atomoxetine (ATM) is a potent norepinephrine (NE) uptake inhibitor and increases both NE and dopamine synaptic levels in prefrontal cortex, where it is thought to exert its beneficial effects on attention and impulsivity. At the behavioral level, ATM has been shown to cause improvements on the measures of executive functions, such as response inhibition, working memory and attentional set shifting across different species. However, the exact mechanism of action for ATM's effects on cognition is still not clear. One possible target for the cognitive enhancing effects of ATM is the noradrenergic locus coeruleus (LC), the only source of NE to key forebrain areas such as cerebral cortex and hippocampus. Although it is known that ATM increases NE availability overall by blocking reuptake of NE, the effects of this agent on impulse activity of LC neurons have not been reported. Here, the effect of ATM (0.1-1 mg/kg, ip) on NE-LC neurons was investigated by recording extracellular activity of LC neurons in isoflurane-anesthetized rats. ATM caused a significant decrease of the tonic activity of LC single-units, although leaving intact the sensory-evoked excitatory component of LC phasic response. Moreover, the magnitude of the inhibitory component of LC response to paw stimulation was increased after 1 mg/kg of ATM and its duration was prolonged at 0.3 mg/kg. Together, these effects of ATM produced an increase in the phasic-to-tonic ratio of LC phasic response to sensory stimulation. ATM also modulated the average sensory-evoked local field potential (LFP) and spike-field coherence in LC depending on the dose tested. The lower dose (0.1 mg/kg) significantly decreased early positive and negative components of the sensory-evoked LFP response. Higher doses (0.3-1 mg/kg) initially increased and then decreased the amplitude of components of the evoked fields, whereas the spike-field coherence was enhanced by 1 mg/kg ATM across frequency bands. Finally, coherence between LC fields and EEG signals was generally increased by 1 mg/kg ATM, whereas 0.1 and 0.3 mg/kg respectively decreased and increased coherence values in specific frequency bands. Taken together these results suggest that ATM effects on LC neuronal activity are dose-dependent, with different doses affecting different aspects of LC firing. This modulation of activity of LC-NE neurons may play a role in the cognitive effects of ATM. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Inhibitory effects of modafinil on emotional memory in mice

Modafinil (MOD), a psychostimulant used to treat narcolepsy, excessive daytime sleepiness, and sleepiness due to obstructive sleep apnea, appears to promote a possible facilitatory effect on cognitive function. In the present study, we investigated the effects of the acute administration of MOD on the different steps of emotional memory formation and usage (acquisition, consolidation and retrieval) as well as the possible participation of the state-dependency phenomenon on the cognitive effects of this compound. Mice were acutely treated with 32, 64 or 128 mg/kg MOD before training or testing or immediately after training and were subjected to the plus-maze discriminative avoidance task. The results showed that although pre-training MOD administration did not exert any effects on learning, the doses of 32 or 64 mg/kg induced emotional memory deficits during testing. Still, the post-training acute administration of the higher doses of MOD (64 and 128 mg/kg) impaired associative memory consolidation. When the drug was administered pre-test, only the 32 mg/kg dose impaired the task retrieval. Importantly, the cognitive impairing effects induced by 32 mg/kg MOD were not related to the phenomenon of state-dependency. In all, our findings provide pre-clinical evidence of potential emotional memory amnesia induced by MOD. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Association of a deficit of arousal with fatigue in multiple sclerosis: effect of modafinil

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system, leading to chronic disability. Fatigue is a common and distressing symptom of MS which is unrelated to its clinical form, stage of development, the degree of disability, or the lesion load on magnetic resonance imaging. Fatigue in MS is associated with excessive daytime sleepiness and autonomic dysfunction. Recently it has been reported that the wakefulness-promoting drug modafinil may relieve fatigue in MS patients and ameliorate the associated cognitive difficulties. However, it is not clear to what extent the anti-fatigue effect of modafinil may be related to its alerting and sympathetic activating effects. We addressed this question by comparing three groups of subjects, MS patients with fatigue, MS patients without fatigue and healthy controls, matched for age and sex, on measures of alertness (self-ratings on the Epworth and Stanford Sleepiness Scales and on a battery of visual analogue scales; critical flicker fusion frequency; Pupillographic Sleepiness Test; choice reaction time) and autonomic function (systolic and diastolic blood pressure, heart rate, pupil diameter), and by examining the effect of a single dose (200 mg) of modafinil on these measures. MS patients with fatigue, compared with healthy controls, had reduced level of alertness on all the tests used; MS patients without fatigue did not differ from healthy controls. MS patients with fatigue had a reduced level of cardiovascular sympathetic activation compared to the other two groups. Modafinil displayed alerting and sympathomimetic effects in all three groups of subjects. As fatigue in MS is associated with reduced levels of alertness and sympathetic activity, modafinil may exert its anti-fatigue effect in MS by correcting these deficiencies. The anti-fatigue effect of modafinil may reflect the activation of the noradrenergic locus coeruleus (LC), since there is evidence that this wakefulness-promoting nucleus is damaged in MS, and that modafinil, probably via the dopaminergic system, can stimulate the LC. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Pharmacotherapy for attention-deficit/hyperactivity disorder: from cells to circuits

Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent disorder of childhood and adulthood, with a considerable impact on public health. There is a substantial pharmacopoeia available for safe and effective treatment of ADHD, and newly available agents diversify the treatment options. With the burgeoning scientific literature addressing the genetic, neurochemical, and neural systems basis for this condition, increasing attention is directed at establishing the neural basis for the efficacy of existing treatments. ADHD remains the only highly prevalent, nondegenerative neuropsychiatric disorder for which effective medications remediate the principal cognitive disturbances in concert with clinical efficacy. Therefore, deeper insight into the neural mechanisms of cognitive remediation may serve to advance treatment development not only in ADHD, but across a wide range of neuropsychiatric disorders in which cognitive dysfunction is a cardinal feature and a strong predictor of clinical outcome. To date, all effective medications for ADHD act on 1 or both of the major catecholamine neurotransmitter systems in the brain. These 2 systems, which arise from subcortical nuclei and use norepinephrine (NE) or dopamine (DA) as transmitters, exert strong modulatory effects on widely distributed cortical-subcortical neural circuits, with important effects on cognition, mood, and behavior, in both health and illness. The present review outlines the actions of ADHD medications from subcellular effects to effects on neural systems and cognition in ADHD patients. This is a very active area of investigation at all phases of the translational cycle, and near-term work is poised to firmly link cellular neuropharmacology to large-scale effects, and point the way toward advances in treatment.

Modafinil improves event related potentials P300 and contingent negative variation after 24 h sleep deprivation

AIMS

The efficacy of modafinil as a countermeasure in the reduction of cognitive decline following 24 h of sleep deprivation (SD) on subjective sleepiness scales, event-related potential (ERP) P300, and contingent negative variation (CNV) was evaluated.

MAIN METHODS

Eleven healthy males, age 25-30 years participated. The experiment was performed in five sessions on different days between 7 and 8a.m. Session 1, baseline recordings; Session 2, after one night's SD; Session 3, 48 h of recovery from SD; Session 4, after 1 week of Session 1, following one night's SD along with modafinil (400mg/day); Session 5, 48 h of recovery after SD+modafinil.

KEY FINDINGS

Subjective sleepiness scores increased significantly after SD as compared to baseline (P<0.01), but remained unaltered after modafinil supplementation. There was an increase in N100 and P300 peak latencies of ERP following SD (P<0.01), which was reduced with modafinil (P<0.05). There was an increase in CNV M100 and P300 peak latencies after SD (P<0.01) which decreased with the use of modafinil (P<0.05). The CNV reaction time increased following SD (P<0.01) and decreased with the use of modafinil (P<0.05). No significant effects on ERP N200, P200 latencies and P200, P300 amplitudes and CNV N100, M200 peak latencies and M100, M200 amplitudes were observed.

SIGNIFICANCE

The results strongly suggest that modafinil in a dose of 400mg/day, reduces the subjective sleepiness and cognitive decline following 24 h of SD.

What should we do about student use of cognitive enhancers? An analysis of current evidence

This article reviews current data on the use of cognition enhancers as study aids in the student population. It identifies gaps and uncertainties in the knowledge required to make a balanced assessment of the need for some form of regulation. The review highlights the weak evidence on the prevalence of use of such drugs, especially outside the US, and the ambiguous evidence for their efficacy in a healthy population. Risks are well documented for the commonly used drugs, but poorly appreciated by users. These include not only the side-effects of the drugs themselves, but risks associated with on-line purchase, which offers no guarantees of authenticity and which for some drugs is illegal. The case for urgent action to regulate use is often linked to the belief that new and more effective drugs are likely to appear in the near future. The evidence for this is weak. However, drugs are not the only possible route to neuroenhancement and action is needed to collect more data on the impact of existing drugs, as well as new technologies, in order to guide society in making a proportionate response to the issue. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

A review of modafinil and armodafinil as add-on therapy in antipsychotic-treated patients with schizophrenia

Schizophrenia is characterized by reality distortion, psychomotor poverty and cognitive disturbances. These characteristics contribute to a lesser social functioning and lower quality of life in patients with schizophrenia. It has been suggested that modafinil and its isomer armodafinil as an add-on strategy to antipsychotic treatment in patients with schizophrenia may improve cognitive functioning, attenuate fatigue, inactiveness and other negative functions as well as weight gain. In this paper we review the literature relevant to the question of whether modafinil and armodafinil are beneficial as add-on therapy in antipsychotic-treated patients with schizophrenia. A total of 15 articles were included in this review; of the 15 articles, 10 were randomized controlled trials (RCTs). Evidence for the use of modafinil or armodafinil as add-on therapy to antipsychotic drugs to alleviate fatigue, sleepiness and inactivity is inconclusive. One cohort study and one out of two single-dose crossover RCTs in which modafinil addition was studied could demonstrate a positive effect. All five RCTs of modafinil (three RCTs) and armodafinil (two RCTs) addition with a longer study duration could not demonstrate a positive effect. With respect to cognitive disturbances, animal models of cognitive deficits show clear improvements with modafinil. In RCTs with a treatment duration of 4 weeks or more, however, no positive effect could be demonstrated on cognitive functioning with modafinil and armodafinil addition. Yet, four single-dose crossover RCTs of modafinil addition show significant positive effects on executive functioning, verbal memory span, visual memory, working memory, spatial planning, slowing in latency, impulse control and recognition of faces expressing sadness and sadness misattribution in the context of disgust recognition. The addition of modafinil or armodafinil to an antipsychotic regime, despite theoretical and preclinical considerations, has not been proved to enhance cognitive function, attenuate fatigue, enhance activity, improve negative symptoms and reduce weight in patients with schizophrenia.

Psychostimulant treatment of cocaine dependence

The use of stimulant medications for the treatment of cocaine dependence is an evolving scientific line of research. To date, the most promising results are with the higher-potency medications, the amphetamine analogues, or a combination of a dopaminergic medication with a contingency management behavioral intervention. The development of effective pharmacotherapies for opioid and nicotine dependence using an agonist replacement approach suggests that these promising findings needs to continue to be vigorously investigated. In clinical trial reports, there are very few instances of cardiovascular adverse events, which suggests that for well-selected patients with cocaine dependence, stimulant replacement therapy can be safe. However, clinical trial eligibility criteria excludes most high-risk patients from participating, and introducing stimulant substitution to the wider treatment community would likely expose more vulnerable patients to the medical risks associated with stimulant treatment while using cocaine. As treatment development research moves forward, attention must be paid to helping clinicians select patients who are most likely to benefit from stimulant substitution treatment and how to identify those at risk. An additional concern with the use of stimulant medication treatment of cocaine dependence is prescribing controlled substances for patients with active substance use disorders. Again, within a clinical trial, medication supplies are monitored and distributed carefully in small quantities. In a community setting, misuse or diversion will be risks associated with prescribing controlled substances to patients with addictive disorders, but therapeutic strategies for monitoring and limiting that risk can be implemented. Psychostimulant pharmacotherapy is a promising line of research for the treatment of cocaine dependence, a condition for which no effective pharmacotherapy has been identified. Further research is required to confirm positive results from single-site trials, in particular the study of amphetamines as a treatment for cocaine dependence. As this literature evolves, strategies to manage the risk of prescribing controlled substances to patients with addictive disorders need to be tested and refined. Biases against using controlled substances as a treatment for cocaine dependence should be challenged, much in the way the use of agonist treatment transformed the treatment of opioid dependence despite initial resistance from the field.

Individual differences are critical in determining modafinil-induced behavioral sensitization and cross-sensitization with methamphetamine in mice

Modafinil is a non-amphetaminic psychostimulant used therapeutically for sleep and psychiatric disorders. However, some studies indicate that modafinil can have addictive properties. The present study examined whether modafinil can produce behavioral sensitization in mice, an experience and drug-dependent behavioral adaptation, and if individual differences play a role in this process. We further tested context-related factors and cross-sensitization between modafinil and methamphetamine. Important individual differences in the behavioral sensitization of Swiss Albino mice were observed after repeated administration of 50 mg/kg modafinil (Experiment 1), or 1 mg/kg methamphetamine (Experiment 2). Only mice classified as sensitized subgroup developed clear behavioral sensitization to the drugs. After a withdrawal period, mice received challenges of modafinil (Experiment 1), or methamphetamine (Experiment 2) and locomotor activity was evaluated in the activity cages (previous context) and in the open field arena (new context) in order to evaluate the context dependency of behavioral sensitization. The expression of sensitization to modafinil, but not to methamphetamine, was affected by contextual testing conditions, since modafinil-sensitized mice only expressed sensitization in the activity cage, but not in the open field. Subsequently, locomotor cross-sensitization between methamphetamine and modafinil was assessed by challenging modafinil-pretreated mice with 1mg/kg methamphetamine (Experiment 1), and methamphetamine-pretreated mice with 50mg/kg modafinil (Experiment 2). We observed a symmetrical cross-sensitization between the drugs only in those mice that were classified as sensitized subgroup. Our findings indicate that repeated exposure to modafinil induces behavioral sensitization only in some animals by similar neurobiological, but not contextual, mechanisms to those of methamphetamine.

A pilot randomised controlled trial of modafinil during acute methamphetamine withdrawal: feasibility, tolerability and clinical outcomes

INTRODUCTION AND AIMS

There are no medications approved for the treatment of methamphetamine withdrawal. Wake-promoting agent modafinil has recently been proposed as a viable option. This paper reports on the results of a pilot study that tested the feasibility of modafinil in an inpatient withdrawal setting during acute methamphetamine withdrawal.

DESIGN AND METHODS

In a double-blind, randomised, placebo-controlled study, 19 methamphetamine dependent participants received modafinil (n = 9) or placebo (n = 10) daily for 7 days (200 mg for the first 5 days and 100 mg on days 6 and 7). Primary outcomes were retention in treatment and severity of withdrawal symptoms. Secondary outcomes were methamphetamine craving, sleep and physiological outcomes.

RESULTS

There were no significant differences between groups on retention in treatment, withdrawal severity, craving, sleep or physiological outcomes. There were no adverse events or side-effects reported.

CONCLUSIONS

Modafinil was found to be tolerable and well accepted by methamphetamine users and feasible for short-term inpatient withdrawal, but the sample was too small to detect treatment effects. Larger trials are needed to establish efficacy.

The ethics of elective psychopharmacology

Pharmacological cognitive enhancers (PCEs) are used to improve cognitive functions, such as attention, learning, memory and planning in patients with impairments in cognition resulting from traumatic brain injury (TBI) or from neuropsychiatric disorders such as Alzheimer's disease (AD), mild cognitive impairment, schizophrenia, and attention deficit hyperactivity disorder (ADHD). Moreover, PCEs have been shown to improve cognition in healthy volunteers with no psychiatric disorders. This article describes the rationale behind the need for their use in neuropsychiatric patients and illustrates how PCEs can ameliorate cognitive impairments, improve quality of life and wellbeing, and therefore reduce the economic burden associated with these disorders. We also describe evidence that PCEs are being used as cognitive enhancers by healthy people. Crucially, as the lifestyle use of these drugs becomes very popular in the healthy population, a final aim is to present an overview of the current and future neuroethical considerations of enhancing the healthy brain. As information regarding their actual use, benefits and harms in various healthy populations is currently lacking, we propose research that aims to obtain relevant empirical data, monitor the short- and long-term effectiveness and side-effects, and initiate accurate surveys to determine current patterns and quantity of usage of PCE drugs by healthy people. Furthermore, in order to instigate a dialogue between neuroethics and neuropsychopharmacology, we urge scientists to explore and communicate the social and ethical implications of their research to the public. Finally, we discuss and highlight other means of enhancing cognition in both patients and healthy adults, including education and physical exercise.

Modafinil reverses phencyclidine-induced deficits in cognitive flexibility, cerebral metabolism, and functional brain connectivity

OBJECTIVE

In the present study, we employ mathematical modeling (partial least squares regression, PLSR) to elucidate the functional connectivity signatures of discrete brain regions in order to identify the functional networks subserving PCP-induced disruption of distinct cognitive functions and their restoration by the procognitive drug modafinil.

METHODS

We examine the functional connectivity signatures of discrete brain regions that show overt alterations in metabolism, as measured by semiquantitative 2-deoxyglucose autoradiography, in an animal model (subchronic phencyclidine [PCP] treatment), which shows cognitive inflexibility with relevance to the cognitive deficits seen in schizophrenia.

RESULTS

We identify the specific components of functional connectivity that contribute to the rescue of this cognitive inflexibility and to the restoration of overt cerebral metabolism by modafinil. We demonstrate that modafinil reversed both the PCP-induced deficit in the ability to switch attentional set and the PCP-induced hypometabolism in the prefrontal (anterior prelimbic) and retrosplenial cortices. Furthermore, modafinil selectively enhanced metabolism in the medial prelimbic cortex. The functional connectivity signatures of these regions identified a unifying functional subsystem underlying the influence of modafinil on cerebral metabolism and cognitive flexibility that included the nucleus accumbens core and locus coeruleus. In addition, these functional connectivity signatures identified coupling events specific to each brain region, which relate to known anatomical connectivity.

CONCLUSIONS

These data support clinical evidence that modafinil may alleviate cognitive deficits in schizophrenia and also demonstrate the benefit of applying PLSR modeling to characterize functional brain networks in translational models relevant to central nervous system dysfunction.

A placebo-controlled study of the modafinil added to risperidone in chronic schizophrenia

RATIONAL

In recent years, evidence suggests that modafinil may be useful for certain symptom domains of schizophrenia, especially for the negative and cognitive symptoms. However, the results are not consistent.

OBJECTIVE

This study was designed to investigate the effect of modafinil added to risperidone in patients with chronic schizophrenia in a double blind and randomized clinical trial.

METHODS

Participants were inpatients males (35) and females (11), ages 20-49 years at two teaching psychiatric hospital in Iran. All patients were in the active phase of the illness and met DSM-IV-TR criteria for schizophrenia. Patients were allocated in a random fashion 23 patients to risperidone 6 mg/day plus modafinil 200 mg/day and 23 patients to risperidone 6 mg/day plus placebo. The principal measure of outcome was the positive and negative syndrome scale (PANSS). Patients were assessed by a psychiatrist at baseline and after 2, 4, 6 and 8 weeks after the start of medication.

RESULTS

The modafinil group had significantly greater improvement in the negative symptoms as well as PANSS total scores over the 8-week trial. Therapy with 200 mg/day of modafinil was well tolerated and no clinically important side effects were observed.

CONCLUSION

The present study indicates modafinil as a potential adjunctive treatment strategy for treatment of schizophrenia particularly the negative symptoms. Nevertheless, results of larger-controlled trials are needed before recommendation for broad clinical application can be made.

Use of modafinil in patients with epilepsy

Fatigue and excessive daytime sleepiness are common symptoms in patients with neurological injury. Modafinil has been shown to ameliorate these symptoms, but its use in patients with seizures has been limited because of safety concerns. Using a large centralized clinical registry, we performed a retrospective chart review of patients with a diagnosis of epilepsy who were given modafinil over a 10-year period. A total of 205 patients were analyzed. There were 91 patients who had seizures while taking modafinil; there was no relationship between modafinil dosage and whether the patient had seizures. There were 6 patients in whom modafinil was discontinued because of concern for seizure exacerbation, and 4 patients had de novo seizures after starting modafinil. In 29 patients with epilepsy only, no major seizure exacerbation was seen. Modafinil is potentially safe in patients with epilepsy, but further prospective studies are needed to fully determine its safety and efficacy.

Biological correlates of post-stroke fatigue: a systematic review

Fatigue is a common and disabling consequence of stroke. Its mechanisms are unknown. Neuroanatomical abnormalities (e.g. white matter lesions, brain atrophy), neuroendocrine dysregulation, neurotransmitter changes and inflammation are associated with fatigue in conditions other than stroke. This review sought to identify published studies describing associations between post-stroke fatigue and these biological factors. We searched Medline, EMBASE, CINAHL, PsycINFO and AMED on October 15 and PubMed on 28 December 2010 and included studies in English that recruited at least 10 patients (>18 years old) with stroke, assessed fatigue and reported its relationship with neuroanatomical abnormalities, hypothalamo-pituitary-adrenal axis dysregulation, neurotransmitter changes or inflammation. Of 4916 citations from the searches, 17 studies met our inclusion criteria. There was no association between white matter lesions, brain atrophy or pathological type of stroke and fatigue (seven studies, n = 4746). The data on relationship between lesion location and fatigue were inconclusive: four (n = 675) of 13 studies (n = 1613) showed associations between fatigue and infratentorial lesion location (brainstem in particular) or basal ganglia stroke. One study reported C-reactive protein levels and found an association with fatigue. No studies reported hypothalamo-pituitary-adrenal axis dysregulation or neurotransmitter changes and fatigue. We could not perform meta-analysis because the studies used different methods of fatigue assessment, examined different populations and had different designs. The biological mechanisms of post-stroke fatigue are uncertain. Further studies are required to determine the relationship between post-stroke fatigue and biological factors.

Differential behavioral profiling of stimulant substances in the rat using the LABORAS™ system

Preclinical testing requires rapid and reliable evaluation of the main in vivo effects of novel test substances usually in rodents. Nevertheless, the techniques primarily used up to now involve either automated measurement of motor activity or direct observation of behavioral effects by extensively trained investigators. The advantages of these approaches are respectively high-throughput and comprehensive behavioral assessment. Nevertheless, motor activity is only one aspect of animal behavior and it cannot predict the full neurobehavioral profile of a substance, whereas direct observation is time-consuming. There is thus a need for novel approaches that combine the advantages of both automatic detection and comprehensive behavioral analysis. In the present study, we used the LABORAS™ system to analyze motor and non-motor behavior in rats administered various stimulant substances with or without known psychotomimetic properties or abuse liability (amphetamine, cocaine dizocilpine (MK-801), ketamine, modafinil and nicotine). The data show that LABORAS™ clearly detects the stimulating effects on motor behaviors of amphetamine, cocaine, dizocilpine and ketamine in a dose- and time-dependent manner. Differential effects of these test substances on non-motor behaviors, such as grooming, eating and drinking could also be detected. Nicotine displayed only slight stimulating effects on locomotion, whereas modafinil was virtually without effect on the behaviors evaluated by the system. These data with different stimulant substances suggest that LABORAS™ presents an advantage over classical methods performing automated measurements restricted to locomotion. Furthermore, the procedure is considerably more rapid than behavioral observation procedures. Characterization of the behavioral profile of test substances using LABORAS™ should therefore accelerate preclinical studies. In addition, the multi-faceted parameters measured by LABORAS™ permit a more detailed comparison of the behavioral profiles of novel substances with standard reference substances, thereby providing important indicators for orienting further substance evaluation and supporting drug development.

Modafinil inhibits K(Ca)3.1 currents and muscle contraction via a cAMP-dependent mechanism

Modafinil has been used as a psychostimulant for the treatment of narcolepsy. However, its primary mechanism of action remains elusive. Therefore, we examined the effects of modafinil on K(Ca)3.1 channels and vascular smooth muscle contraction. K(Ca)3.1 currents and channel activity were measured using a voltage-clamp technique and inside-out patches in mouse embryonic fibroblast cell line, NIH-3T3 fibroblasts. Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) concentration was measured, and the phosphorylation of K(Ca)3.1 channel protein was examined using western blotting in NIH-3T3 fibroblasts and/or primary cultured mouse aortic smooth muscle cells (SMCs). Muscle contractions were recorded from mouse aorta and rat pulmonary artery by using a myograph developed in-house. Modafinil was found to inhibit K(Ca)3.1 currents in a concentration-dependent manner, and the half-maximal inhibition (IC(50)) of modafinil for the current inhibition was 6.8 ± 0.7 nM. The protein kinase A (PKA) activator forskolin also inhibited K(Ca)3.1 currents. The inhibitory effects of modafinil and forskolin on K(Ca)3.1 currents were blocked by the PKA inhibitors PKI(14-22) or H-89. In addition, modafinil relaxed blood vessels (mouse aorta and rat pulmonary artery) in a concentration-dependent manner. Modafinil increased cAMP concentrations in NIH-3T3 fibroblasts or primary cultured mouse aortic SMCs and phosphorylated K(Ca)3.1 channel protein in NIH-3T3 fibroblasts. However, open probability and single-channel current amplitudes of K(Ca)3.1 channels were not changed by modafinil. From these results, we conclude that modafinil inhibits K(Ca)3.1 channels and vascular smooth muscle contraction by cAMP-dependent phosphorylation, suggesting that modafinil can be used as a cAMP-dependent K(Ca)3.1 channel blocker and vasodilator.

Polymorphisms of ADORA2A modulate psychomotor vigilance and the effects of caffeine on neurobehavioural performance and sleep EEG after sleep deprivation

BACKGROUND AND PURPOSE

Prolonged wakefulness impairs sustained vigilant attention, measured with the psychomotor vigilance task (PVT), and induces a compensatory increase in sleep intensity in recovery sleep, quantified by slow-wave activity (SWA) in the sleep electroencephalogram (EEG). These effects of sleep deprivation are counteracted by the adenosine receptor antagonist caffeine, implying involvement of the adenosine neuromodulator/receptor system. To examine a role for adenosine A(2A) receptors, we investigated whether variation of the A(2A) receptor gene (ADORA2A) modified effects of caffeine on PVT and SWA after sleep deprivation.

EXPERIMENTAL APPROACH

A haplotype analysis of eight single-nucleotide polymorphisms of ADORA2A was performed in 82 volunteers. In 45 young men carrying five different allele combinations, we investigated the effects of prolonged waking and 2 × 200 mg caffeine or 2 × 100 mg modafinil on psychomotor vigilance, sleepiness, and the waking and sleep EEG.

KEY RESULTS

Throughout extended wakefulness, the carriers of haplotype HT4 performed faster on the PVT than carriers of non-HT4 haplotype alleles. In haplotype HT4, caffeine failed to counteract the waking-induced impairment of PVT performance and the rebound of SWA in recovery sleep. However, caffeine was effective in non-HT4 allele carriers, and modafinil reduced the consequences of prolonged waking, independently of ADORA2A haplotype.

CONCLUSIONS AND IMPLICATIONS

Common genetic variation of ADORA2A is an important determinant of psychomotor vigilance in rested and sleep-deprived state. It also modulates individual responses to caffeine after sleep deprivation. These findings demonstrate a role for adenosine A(2A) receptors in the effects of prolonged wakefulness on vigilant attention and the sleep EEG.

Acute modafinil effects on attention and inhibitory control in methamphetamine-dependent humans

OBJECTIVE

Individuals who are methamphetamine dependent exhibit higher rates of cognitive dysfunction than healthy people who do not use methamphetamine, and this dysfunction may have a negative effect on the success of behavioral treatments for the disorder. Therefore, a medication that improves cognition, such as modafinil (Provigil), may serve as a useful adjunct to behavioral treatments for methamphetamine dependence. Although cognitive-enhancing effects of modafinil have been reported in several populations, little is known about the effects of modafinil in methamphetamine-dependent individuals. We thus sought to evaluate the effects of modafinil on the cognitive performance of methamphetamine-dependent and healthy individuals.

METHOD

Seventeen healthy subjects and 24 methamphetamine- dependent subjects participated in this randomized, double-blind, placebo-controlled, crossover study. Effects of modafinil (200 mg, single oral dose) were assessed on participants' performance on tests of inhibitory control, working memory, and processing speed/attention.

RESULTS

Across subjects, modafinil improved performance on a test of sustained attention, with no significant improvement on any other cognitive tests. However, within the methamphetamine-dependent group only, participants with a high baseline frequency of methamphetamine use demonstrated a greater effect of modafinil on tests of inhibitory control and processing speed than those participants with low baseline use of methamphetamine.

CONCLUSIONS

Although modafinil produced limited effects across all participants, methamphetamine-dependent participants with a high baseline use of methamphetamine demonstrated significant cognitive improvement on modafinil relative to those with low baseline methamphetamine use. These results add to the findings from a clinical trial that suggested that modafinil may be particularly useful in methamphetamine-dependent subjects who use the drug frequently.

Assessment of brain activity during memory encoding in a narcolepsy patient on and off modafinil using normative fMRI data

We present behavioral and functional magnetic resonance imaging (fMRI) findings of a 20-year-old female with narcolepsy who completed a standardized fMRI-adapted face memory task both 'off' and 'on' modafinil compared to a normative sample (N = 38). The patient showed poor recognition performance off modafinil (z = -2.03) but intact performance on modafinil (z = 0.78). fMRI results showed atypical activation during memory encoding off modafinil, with frontal lobe hypoactivity, but hippocampal hyperactivity, whereas all brain regions showed more normalized activation on modafinil. Results from this limited study suggest hippocampal and frontal alterations in individuals with narcolepsy. Further, the results suggest the hypothesis that modafinil may affect brain activation in some people with narcolepsy.

Modulation of fronto-cortical activity by modafinil: a functional imaging and fos study in the rat

Modafinil (MOD) is a wake-promoting drug with pro-cognitive properties. Despite its increasing use, the neuronal substrates of MOD action remain elusive. In particular, animal studies have highlighted a putative role of diencephalic areas as primary neuronal substrate of MOD action, with inconsistent evidence of recruitment of fronto-cortical areas despite the established pro-cognitive effects of the drug. Moreover, most animal studies have employed doses of MOD of limited clinical relevance. We used pharmacological magnetic resonance imaging (phMRI) in the anesthetized rat to map the circuitry activated by a MOD dose producing clinically relevant plasma exposure, as here ascertained by pharmacokinetic measurements. We observed prominent and sustained activation of the prefrontal and cingulate cortex, together with weaker but significant activation of the somatosensory cortex, medial thalamic domains, hippocampus, ventral striatum and dorsal raphe. Correlation analysis of phMRI data highlighted enhanced connectivity within a neural network including dopamine projections from the ventral tegmental area to the nucleus accumbens. The pro-arousing effect of MOD was assessed using electroencephalographic recording under anesthetic conditions comparable to those used for phMRI, together with the corresponding Fos immunoreactivity distribution. MOD produced electroencephalogram desynchronization, resulting in reduced delta and increased theta frequency bands, and a pattern of Fos induction largely consistent with the phMRI study. Altogether, these findings show that clinically relevant MOD doses can robustly activate fronto-cortical areas involved in higher cognitive functions and a network of pro-arousing areas, which provide a plausible substrate for the wake-promoting and pro-cognitive effects of the drug.

Examining reports and policies on cognitive enhancement: approaches, rationale, and recommendations

The phenomenon of cognitive enhancement is attracting attention in bioethics literature and beyond, in public policy. In response, three bodies--the British Medical Association (BMA); the Commission de l'éthique de la Science et de la technologie (CEST) du Québec; the American Academy of Neurology (AAN)--have produced reports and guidance on this topic. To gain insights into different public policy approaches, rationales, and recommendations on the topic, we analyzed these reports in depth. We found convergence on the definition (with the exception of the CEST) of cognitive enhancement. However, we noted a lack of critical reflection with respect to the underlying rationale for developing these reports, i.e., that cognitive enhancement practices are rampant and represent major social changes. As it currently stands, cognitive enhancement is constituted in a way that challenges the creation of coherent and effective policy recommendations. However, policy makers should not simply wait for definitional consensus and hope that on balance the benefits turn out to be greater than the risks. Some components of cognitive enhancement could be reduced down to clearly identified policy targets to be further examined. Then, if appropriate, policy should be created that is, amongst other criteria, beneficial to the majority of the population.

Are prescription stimulants "smart pills"? The epidemiology and cognitive neuroscience of prescription stimulant use by normal healthy individuals

Use of prescription stimulants by normal healthy individuals to enhance cognition is said to be on the rise. Who is using these medications for cognitive enhancement, and how prevalent is this practice? Do prescription stimulants in fact enhance cognition for normal healthy people? We review the epidemiological and cognitive neuroscience literatures in search of answers to these questions. Epidemiological issues addressed include the prevalence of nonmedical stimulant use, user demographics, methods by which users obtain prescription stimulants, and motivations for use. Cognitive neuroscience issues addressed include the effects of prescription stimulants on learning and executive function, as well as the task and individual variables associated with these effects. Little is known about the prevalence of prescription stimulant use for cognitive enhancement outside of student populations. Among college students, estimates of use vary widely but, taken together, suggest that the practice is commonplace. The cognitive effects of stimulants on normal healthy people cannot yet be characterized definitively, despite the volume of research that has been carried out on these issues. Published evidence suggests that declarative memory can be improved by stimulants, with some evidence consistent with enhanced consolidation of memories. Effects on the executive functions of working memory and cognitive control are less reliable but have been found for at least some individuals on some tasks. In closing, we enumerate the many outstanding questions that remain to be addressed by future research and also identify obstacles facing this research.

Review of pharmacological treatment in mood disorders and future directions for drug development

After a series of serendipitous discoveries of pharmacological treatments for mania and depression several decades ago, relatively little progress has been made for novel hypothesis-driven drug development in mood disorders. Multifactorial etiologies of, and lack of a full understanding of, the core neurobiology of these conditions clearly have contributed to these development challenges. There are, however, relatively novel targets that have raised opportunities for progress in the field, such as glutamate and cholinergic receptor modulators, circadian regulators, and enzyme inhibitors, for alternative treatment. This review will discuss these promising new treatments in mood disorders, the underlying mechanisms of action, and critical issues of their clinical application. For these new treatments to be successful in clinical practice, it is also important to design innovative clinical trials that identify the specific actions of new drugs, and, ideally, to develop biomarkers for monitoring individualized treatment response. It is predicted that future drug development will identify new agents targeting the molecular mechanisms involved in the pathophysiology of mood disorders.

Practical use and risk of modafinil, a novel waking drug

OBJECTIVES

Modafinil is a waking drug prescribed to narcolepsy patients, but its usage among healthy individuals is increasing to enhance their alertness or to mitigate fatigue. This study was conducted to investigate practical use and toxic effects on neuro-immune interaction of modafinil.

METHODS

This study reviewed the significance of psychoactive drugs, and discussed the benefits and risks of the application of modafinil, which seems to be ideal as an anti-psychotic or anti-fatigue agent.

RESULTS

Modafinil is known to have less or no adverse effects than those found in traditional psychostimulants such as amphetamine, methylphenidate or cocaine. It can be applied as an anti-psychotic or anti-fatigue agent. However, the waking mechanism of modafinil is yet to be fully revealed. Recent studies reported that modafinil may be subject to abuse and addiction. In addition prolonged sleeplessness induces stress responses and impairs immune function.

CONCLUSIONS

Modafinil can be used by anyone, who wishes to work late, stay awake, enhance their cognitive reactions, or brighten their moods. Users may already be under a great level of stress, i.e. cancer patients or soldiers in a battle field. A psychoneuroimmunological approach is thus needed to investigate the multi-functional effects of modafinil.

ADHD: current and future therapeutics

The stimulants, amphetamine and methylphenidate, have long been the mainstay of attention-deficit hyperactivity disorder (ADHD) therapy. They are rapidly effective and are generally the first medications selected by physicians. In the development of alternative pharmacological approaches, drug candidates have been evaluated with a wide diversity of mechanisms. All of these developments have contributed real progress in the field, but there is still much room for improvement and unmet clinical need in ADHD pharmacotherapy. The availability of a wide range of compounds with a high degree of specificity for individual monoamines (dopamine and noradrenaline) and/or different pharmacological mechanisms has refined our understanding of the essential elements for optimum pharmacological effect in managing ADHD. In this chapter, we review the pharmacology of the different classes of drug used to treat ADHD and provide a neurochemical rationale, predominantly from the use of in vivo microdialysis experiments, to explain their relative efficacy and potential to elicit side effects. In addition, we will consider how predictions based on results from animal models translate into clinical outcomes. The treatment of ADHD is also described from the perspective of the physician. Finally, the new research development for drugs to treat ADHD is discussed.

Neural and behavioral endophenotypes in ADHD

In recent years, descriptive symptom-based approaches of attention deficit hyperactivity disorder (ADHD) have been increasingly replaced by more sophisticated endophenotype-based strategies, better suited to investigate its pathophysiological basis, which is inherently heterogeneous. Measurements derived from neuroimaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) constitute endophenotypes of growing interest, capable of providing unprecedented windows on neurochemical and neuroanatomical components of psychiatric conditions. This chapter reviews the current state of knowledge regarding putative neural and behavioral endophenotypes of ADHD, across the lifespan. To this end, recent evidence drawn from molecular and structural neuroimaging studies are discussed in the light of widely accepted neuropsychological and pharmacological models of ADHD.

Convenient synthesis and biological evaluation of modafinil derivatives: benzhydrylsulfanyl and benzhydrylsulfinyl [1,2,3]triazol-4-yl-methyl esters

Simple synthesis and biological activities of modafinil derivatives are described. The key reactions include condensation of acid and propargyl alcohol, subsequent 1,3-dipolar cycloaddition reaction of alkynes and (3-azido-propyl)cyclohexane or (4-azido-butyl)benzene in the presence of sodium ascorbate and CuSO₄·5H₂O in excellent yield. They were then evaluated for the suppression of LPS-induced NO generation in vitro. It was found that all compounds showed moderate effects for suppression of LPS-induced NO generation.

The atypical stimulant and nootropic modafinil interacts with the dopamine transporter in a different manner than classical cocaine-like inhibitors

Modafinil is a mild psychostimulant with pro-cognitive and antidepressant effects. Unlike many conventional stimulants, modafinil has little appreciable potential for abuse, making it a promising therapeutic agent for cocaine addiction. The chief molecular target of modafinil is the dopamine transporter (DAT); however, the mechanistic details underlying modafinil's unique effects remain unknown. Recent studies suggest that the conformational effects of a given DAT ligand influence the magnitude of the ligand's reinforcing properties. For example, the atypical DAT inhibitors benztropine and GBR12909 do not share cocaine's notorious addictive liability, despite having greater binding affinity. Here, we show that the binding mechanism of modafinil is different than cocaine and similar to other atypical inhibitors. We previously established two mutations (W84L and D313N) that increase the likelihood that the DAT will adopt an outward-facing conformational state—these mutations increase the affinity of cocaine-like inhibitors considerably, but have little or opposite effect on atypical inhibitor binding. Thus, a compound's WT/mutant affinity ratio can indicate whether the compound preferentially interacts with a more outward- or inward-facing conformational state. Modafinil displayed affinity ratios similar to those of benztropine, GBR12909 and bupropion (which lack cocaine-like effects in humans), but far different than those of cocaine, β-CFT or methylphenidate. Whereas treatment with zinc (known to stabilize an outward-facing transporter state) increased the affinity of cocaine and methylphenidate two-fold, it had little or no effect on the binding of modafinil, benztropine, bupropion or GBR12909. Additionally, computational modeling of inhibitor binding indicated that while β-CFT and methylphenidate stabilize an “open-to-out” conformation, binding of either modafinil or bupropion gives rise to a more closed conformation. Our findings highlight a mechanistic difference between modafinil and cocaine-like stimulants and further demonstrate that the conformational effects of a given DAT inhibitor influence its phenomenological effects.

Addictive potential of modafinil and cross-sensitization with cocaine: a pre-clinical study

Repeated or even a single exposure to drugs of abuse can lead to persistent locomotor sensitization, which is the result of an abundance of neuroplastic changes occurring within the circuitry involved in motivational behavior and is thought to play a key role in certain aspects of drug addiction. There is substantial controversy about the addictive potential of modafinil, a wake-promoting drug used to treat narcolepsy that is increasingly being used as a cognitive enhancer and has been proposed as a pharmacotherapy for cocaine dependence. Male mice were used to investigate the ability of modafinil to induce locomotor sensitization after repeated or single administration in mice. Bidirectional cross-sensitization with cocaine and modafinil-induced conditioned place preference were also evaluated. Both repeated and single exposure to moderate and high doses of modafinil produced a pronounced locomotor sensitization that cross-sensitized in a bidirectional way with cocaine. Remarkably, when cocaine and modafinil were repeatedly administered sequentially, their behavioral sensitization was additive. Supporting these behavioral sensitization data, modafinil produced a pronounced conditioned place preference in the mouse. Taken together, the present findings provide pre-clinical evidence for the addictive potential of modafinil. Our data also strongly suggest that similar neural substrates are involved in the psychomotor/rewarding effects of modafinil and cocaine.

Assaying dissociable elements of behavioural inhibition and impulsivity: translational utility of animal models

Inhibition is a fundamental property of behaviour required for flexible responding and humans have evolved executive brain systems that can engage inhibitory processes in order to reduce interference from irrelevant distracting stimuli, block unwanted memories and emotions and suppress inappropriate choices and actions. Without the efficient operation of these inhibitory mechanisms behaviour can become maladaptive, as seen in a large range of disorders where subjects exhibit impulsive responding, such as ADHD, mania, chronic substance abuse and schizophrenia. Animal models are making an increasing contribution to our understanding of the psychology and underlying neurobiology of behavioural inhibition and impulsivity. Here, in this short article we summarise work conducted with rat models, and also discuss recent progress in exploiting the potential of genetically engineered mice. The data so far emphasise the relatively high translational relevance of animal models in this area of behavioural neuroscience. The findings add weight to the existence of dissociable components of impulsive behaviour, they inform the human literature, and may be of significant use in the development of drug therapies to treat the many disorders where failures in behavioural inhibition are prominent.

Chemotherapy and cognitive impairment: treatment options

Chemotherapy has improved survival rates in patients with many of the common cancers. However, there is reliable evidence that, as a result of treatment, a subset of cancer survivors experience cognitive problems that can last for many years after the completion of chemotherapy. The etiology of this phenomenon is largely unknown, and currently there are no proven treatments. This article explores the clinical and preclinical literature on potential therapies for chemotherapy-induced cognitive impairments. Emerging results suggest that both pharmacological and behavioral approaches may offer patients some benefits. However, research in this area has been limited and is sometimes fraught with methodological flaws. As a result, it is difficult to draw definite conclusions regarding treatment efficacy. These issues, along with predictors of cognitive decline, are discussed in the light of possible interventions.

Alzheimer's disease and age-related memory decline (preclinical)

An unfortunate result of the rapid rise in geriatric populations worldwide is the increasing prevalence of age-related cognitive disorders such as Alzheimer's disease (AD). AD is a devastating neurodegenerative illness that is characterized by a profound impairment of cognitive function, marked physical disability, and an enormous economic burden on the afflicted individual, caregivers, and society in general. The rise in elderly populations is also resulting in an increase in individuals with related (potentially treatable) conditions such as "Mild Cognitive Impairment" (MCI) which is characterized by a less severe (but abnormal) level of cognitive impairment and a high-risk for developing dementia. Even in the absence of a diagnosable disorder of cognition (e.g., AD and MCI), the perception of increased forgetfulness and declining mental function is a clear source of apprehension in the elderly. This is a valid concern given that even a modest impairment of cognitive function is likely to be associated with significant disability in a rapidly evolving, technology-based society. Unfortunately, the currently available therapies designed to improve cognition (i.e., for AD and other forms of dementia) are limited by modest efficacy and adverse side effects, and their effects on cognitive function are not sustained over time. Accordingly, it is incumbent on the scientific community to develop safer and more effective therapies that improve and/or sustain cognitive function in the elderly allowing them to remain mentally active and productive for as long as possible. As diagnostic criteria for memory disorders evolve, the demand for pro-cognitive therapeutic agents is likely to surpass AD and dementia to include MCI and potentially even less severe forms of memory decline. The purpose of this review is to provide an overview of the contemporary therapeutic targets and preclinical pharmacologic approaches (with representative drug examples) designed to enhance memory function.

The likelihood of cognitive enhancement

Whether drugs that enhance cognition in healthy individuals will appear in the near future has become a topic of considerable interest. We address this possibility using a three variable system (psychological effect, neurobiological mechanism, and efficiency vs. capabilities) for classifying candidates. Ritalin and modafinil, two currently available compounds, operate on primary psychological states that in turn affect cognitive operations (attention and memory), but there is little evidence that these effects translate into improvements in complex cognitive processing. A second category of potential enhancers includes agents that improve memory encoding, generally without large changes in primary psychological states. Unfortunately, there is little information on how these compounds affect cognitive performance in standard psychological tests. Recent experiments have identified a number of sites at which memory drugs could, in principle, manipulate the cell biological systems underlying the learning-related long-term potentiation (LTP) effect; this may explain the remarkable diversity of memory promoting compounds. Indeed, many of these agents are known to have positive effects on LTP. A possible third category of enhancement drugs directed specifically at integrated cognitive operations is nearly empty. From a neurobiological perspective, two plausible candidate classes have emerged that both target the fast excitatory transmission responsible for communication within cortical networks. One acts on nicotinic receptors (alpha7 and alpha4) that regulate release of the neurotransmitter glutamate while the other ('ampakines') allosterically modulates the glutamate receptors mediating the post-synaptic response (EPSCs). Brain imaging in primates has shown that ampakines expand cortical networks engaged by a complex task; coupled with behavioral data, these findings provide evidence for the possibility of generating new cognitive capabilities. Finally, we suggest that continuing advances in behavioral sciences provide new opportunities for translational work, and that discussions of the social impact of cognitive enhancers have failed to consider the distinction between effects on efficiency vs. new capabilities.

The effect of adjunctive armodafinil on cognitive performance and psychopathology in antipsychotic-treated patients with schizophrenia/schizoaffective disorder: a randomized, double-blind, placebo-controlled trial

BACKGROUND

The efficacy, safety and tolerability of adjunctive armodafinil for cognitive performance, and negative and affective symptoms, were examined in 60 patients with schizophrenia or schizoaffective disorder.

METHOD

This was a 6-week, double-blind, placebo-controlled, fixed dose trial of armodafinil (150 mg/d) augmentation in patients with clinically stable schizophrenia or schizoaffective disorder. Cognition, psychopathology, alertness/wakefulness and adverse effects were assessed with standardized rating instruments. The primary endpoint was performance on measures of attention/vigilance.

RESULTS

Patients were randomly allocated to adjunctive armodafinil or placebo. There was a significant Drug×Time interaction effect for attention/vigilance, due to modest non-significant worsening in the armodafinil group and improvement in the armodafinil group [CPT-Pairs d', F(1,40)=6.2, p=0.017]. However, it became non-significant after correction for multiple comparisons. There were no differences between armodafinil and placebo in other cognitive domains or psychopathology measures. However, armodafinil was associated with significant improvement in the Scale for the Assessment of Negative Symptoms (SANS) anhedonia-asociality [F(1,41)=4.1, p=0.05].

CONCLUSIONS

There were no significant differences in neurocognitive measures between adjunctive armodafinil and placebo in this 6-week study. Armodafinil improved anhedonia-asociality, but not other negative symptom domains.

The treatment of cognitive impairment in schizophrenia

Cognitive deficits are major contributors to disability in schizophrenia. Many pharmacologic targets have been identified for cognitive enhancing agents, including receptors involved in dopaminergic, glutamatergic, GABAergic, serotonergic and cholinergic neurotransmission. In addition, new approaches to drug development have been directed towards neuroprotection and the facilitation of neuroplasticity. While several pharmacologic agents and cognitive remediation have shown promise in early trials, no treatment has yet demonstrated efficacy in large replication trials. The experience with different pharmacologic targets is reviewed and methodologic issues are discussed with recommendations for future research.

Cognitive enhancers in the treatment of substance use disorders: clinical evidence

Attenuation of drug reward has been the major focus of medication development in the addiction area to date. With the growth of research in the area of cognitive neuroscience, the importance of executive function and inhibitory cognitive control in addictive disorders is becoming increasingly apparent. An emerging strategy in the pharmacotherapy of addictions and other psychiatric disorders involves the use of medications that improve cognitive function. In particular, agents that facilitate inhibitory and attentional control, improve abstraction, planning and mental flexibility could be beneficial in the treatment of substance use disorders. Because there are multiple neurotransmitter systems involved in the regulation of cognitive function, agents from a number of drug classes have been tested. In particular, agents acting through the cholinergic, adrenergic and glutamatergic systems have shown potential for improving cognitive function in a number of psychiatric and neurologic disorders, but most of these agents have not been tested in the treatment of individuals with substance use disorders. This manuscript provides a review of clinical data supporting the use of the major classes of cognitive enhancing agents in substance use disorders. Agents that have shown promise in cognitive enhancement in other disorders, and have a theoretical or mechanistic rationale for application to substance use disorders are also highlighted.

Cognitive enhancers for anxiety disorders

Cognitive-behavioral therapy is an effective intervention for anxiety disorders. However, a significant number of people do not respond or only show partial response even after an adequate course of the treatment. Recent research has shown that the efficacy of the intervention can be improved by the use of cognitive enhancers that augment the core learning processes of cognitive-behavior therapy. This manuscript provides a review of the current state of cognitive enhancers for the treatment of anxiety disorders.

Cognitive dysfunction in depression: neurocircuitry and new therapeutic strategies

Major depressive disorder (MDD) is a disabling medical condition associated with significant morbidity, mortality and public health costs. However, neurocircuitry abnormalities underlying depression remain incompletely understood and consequently current treatment options are unfortunately limited in efficacy. Recent research has begun to focus specifically on cognitive aspects of depression and potential neurobiological correlates. Two fundamental types of cognitive dysfunction observed in MDD are cognitive biases, which include distorted information processing or attentional allocation toward negative stimuli, and cognitive deficits, which include impairments in attention, short-term memory and executive functioning. In this article, we present a selective review of current research findings in these domains and examine neuroimaging research that is beginning to characterize the neurocircuitry underlying these biases and deficits. We propose that deficient cognitive functioning, attention biases and the sustained negative affect characteristic of MDD can be understood as arising in part from dysfunctional prefrontal-subcortical circuitry and related disturbances in the cognitive control of emotion. Finally, we highlight potential new pharmacological and non-pharmacological therapeutic strategies for MDD based on an evolving mechanistic understanding of the disorder.

The roles of dopamine and noradrenaline in the pathophysiology and treatment of attention-deficit/hyperactivity disorder

Through neuromodulatory influences over fronto-striato-cerebellar circuits, dopamine and noradrenaline play important roles in high-level executive functions often reported to be impaired in attention-deficit/hyperactivity disorder (ADHD). Medications used in the treatment of ADHD (including methylphenidate, dextroamphetamine and atomoxetine) act to increase brain catecholamine levels. However, the precise prefrontal cortical and subcortical mechanisms by which these agents exert their therapeutic effects remain to be fully specified. Herein, we review and discuss the present state of knowledge regarding the roles of dopamine (DA) and noradrenaline in the regulation of corticostriatal circuits, with a focus on the molecular neuroimaging literature (both in ADHD patients and in healthy subjects). Recent positron emission tomography evidence has highlighted the utility of quantifying DA markers, at baseline or following drug administration, in striatal subregions governed by differential cortical connectivity. This approach opens the possibility of characterizing the neurobiological underpinnings of ADHD (and associated cognitive dysfunction) and its treatment by targeting specific neural circuits. It is anticipated that the application of refined and novel positron emission tomography methodology will help to disentangle the overlapping and dissociable contributions of DA and noradrenaline in the prefrontal cortex, thereby aiding our understanding of ADHD and facilitating new treatments.

Dopamine receptor mediation of the exploratory/hyperactivity effects of modafinil

Modafinil (2-((diphenylmethyl)sulfinyl)acetamide) is described as an atypical stimulant and is a putative cognition enhancer for schizophrenia, but the precise mechanisms of action remain unclear. Receptor knockout (KO) mice offer an opportunity to identify receptors that contribute to a drug-induced effect. Here we examined the effects of modafinil on exploration in C57BL/6J mice, in dopamine drd1, drd2, drd3, and drd4 wild-type (WT), heterozygous (HT), and KO mice, and in 129/SJ mice pretreated with the drd1 antagonist SCH23390 using a cross-species test paradigm based on the behavioral pattern monitor. Modafinil increased activity, specific exploration (rearing), and the smoothness of locomotor paths (reduced spatial d) in C57BL/6J and 129/SJ mice (increased holepoking was also observed in these mice). These behavioral profiles are similar to that produced by the dopamine transporter inhibitor GBR12909. Modafinil was ineffective at increasing activity in male drd1 KOs, rearing in female drd1 KOs, or reducing spatial d in all drd1 KOs, but produced similar effects in drd1 WT and HT mice as in C57BL/6J mice. Neither dopamine drd2 nor drd3 mutants attenuated modafinil-induced effects. Drd4 mutants exhibited a genotype dose-dependent attenuation of modafinil-induced increases in specific exploration. Furthermore, the drd1 KO effects were largely supported by the SCH23390 study. Thus, the dopamine drd1 receptor appears to exert a primary role in modafinil-induced effects on spontaneous exploration, whereas the dopamine drd4 receptor appears to be important for specific exploration. The modafinil-induced alterations in exploratory behavior may reflect increased synaptic dopamine and secondary actions mediated by dopamine drd1 and drd4 receptors.

Cognitive enhancers for the treatment of ADHD

Attention-deficit hyperactivity disorder (ADHD) is associated with multiple cognition-related phenotypic features in both children and adults. This review aims to clarify the role of cognition in ADHD and how prevailing treatments, which are often highly effective at reducing the clinical symptoms of the disorder, fare in modulating ADHD-related cognitive processes. First, we consider how the broad construct of cognition can be conceptualized in the context of ADHD. Second, we review the available evidence for how a range of both pharmacological and non-pharmacological interventions have fared with respect to enhancing cognition in individuals affected by this pervasive disorder. Findings from the literature suggest that the effects across a broad range of pharmacological and non-pharmacological interventions on the characteristic symptoms of ADHD can be distinguished from their effects on cognitive impairments. As such the direct clinical relevance of cognition enhancing effects of different interventions is somewhat limited. Recommendations for future research are discussed, including the identification of cognition-related endophenotypes, the refinement of the ADHD clinical phenotype, and studying the difference between acute and chronic treatment regimens.