A review of the effects of modafinil on cognition in schizophrenia

Baseline prepulse inhibition dependency of orexin A and REM sleep deprivation

RATIONALE

Prepulse inhibition (PPI) impairment reflects sensorimotor gating problems, i.e. in schizophrenia. This study aims to enlighten the role of orexinergic regulation on PPI in a psychosis-like model.

OBJECTIVES

In order to understand the impact of orexinergic innervation on PPI and how it is modulated by age and baseline PPI (bPPI), chronic orexin A (OXA) injections was carried on non-sleep-deprived and sleep-deprived rats that are grouped by their bPPI.

METHODS

bPPI measurements were carried on male Wistar rats on P45 or P90 followed by grouping into low-PPI and high-PPI rats. The rats were injected with OXA twice per day for four consecutive days starting on P49 or P94, while the control groups received saline injections. 72 h REMSD was carried on via modified multiple platform technique on P94 and either OXA or saline was injected during REMSD. PPI tests were carried out 30 min. after the last injection.

RESULTS

Our previous study with acute OXA injection after REMSD without bPPI grouping revealed that low OXA doses might improve REMSD-induced PPI impairment. Our current results present three important conclusions: (1) The effect of OXA on PPI is bPPI-dependent and age-dependent. (2) The effect of REMSD is bPPI-dependent. (3) The effect of OXA on PPI after REMSD also depends on bPPI.

CONCLUSION

Orexinergic regulation of PPI response with and without REMSD can be predicted by bPPI levels. Our findings provide potential insights into the regulation of sensorimotor gating by sleep/wakefulness systems and present potential therapeutic targets for the disorders, where PPI is disturbed.

Modafinil, an atypical CNS stimulant?

Modafinil is a central nervous system stimulant approved for the treatment of narcolepsy and sleep disorders. Due to its wide range of biochemical actions, modafinil has been explored for other potential therapeutic uses. Indeed, it has shown promise as a therapy for cognitive disfunction resulting from neurologic disorders like ADHD, and as a smart drug in non-medical settings. The mechanism(s) of actions underlying the therapeutic efficacy of this agent remains largely elusive. Modafinil is known to inhibit the dopamine transporter, thus decreasing dopamine reuptake following neuronal release, an effect shared by addictive psychostimulants. However, modafinil is unique in that only a few cases of dependence on this drug have been reported, as compared to other psychostimulants. Moreover, modafinil has been tested, with some success, as a potential therapeutic agent to combat psychostimulant and other substance use disorders. Modafinil has additional, but less understood, actions on other neurotransmitter systems (GABA, glutamate, serotonin, norepinephrine, etc.). These interactions, together with its ability to activate selected brain regions, are likely one of the keys to understand its unique pharmacology and therapeutic activity as a CNS stimulant. In this chapter, we outline the pharmacokinetics and pharmacodynamics of modafinil that suggest it has an "atypical" CNS stimulant profile. We also highlight the current approved and off label uses of modafinil, including its beneficial effects as a treatment for sleep disorders, cognitive functions, and substance use disorders.

Determination of modafinil in rat plasma by UPLC-MS/MS and a study of its pharmacokinetics and bioavailability

Modafinil has a strong and long-lasting awakening effect. Short-term use can improve cognitive and work efficiency. Therefore, it has been known to be abused by students and parents as a “smart drug.” It is in the first category of psychotropic drugs and strictly controlled. To detect modafinil in rat plasma and study the differences in the pharmacokinetics of modafinil between oral and sublingual administration in rats, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed. Rats were injected with modafinil by oral gavage and sublingual vein, respectively, blood was collected within a certain period, and the plasma was obtained by centrifugation. Midazolam was used as the internal standard, and the concentration of modafinil in the plasma was determined by UPLC-MS/MS, where a drug-time curve was created to calculate the pharmacokinetic parameters. The standard curve for modafinil ranged from 1 to 2000 ng mL−1 with good linearity. The intra-day accuracy of modafinil was between 86% and 104%, and the intra-day accuracy was between 90% and 103%. Intra-day precision (RSD%) was less than 15%, inter-day precision (RSD%) was less than 15%. The matrix effect was between 93% and 102%, and the recovery was greater than 91%. The UPLC-MS/MS method established in this work has good selectivity and high sensitivity, and the UPLC-MS/MS method was successfully applied to the pharmacokinetics of modafinil by oral gavage and sublingual injection in rats. The bioavailability of modafinil was calculated to be 55.8%.

The clozapine to norclozapine ratio: a narrative review of the clinical utility to minimize metabolic risk and enhance clozapine efficacy

Introduction: Clozapine remains the most effective antipsychotic for treatment-refractory schizophrenia. However, ~40% of the patients respond insufficiently to clozapine. Clozapine's effects, both beneficial and adverse, have been proposed to be partially attributable to its main metabolite, N-desmethylclozapine (NDMC). However, the relation of the clozapine to norclozapine ratio (CLZ:NDMC; optimally defined as ~2) to clinical response and metabolic outcomes is not clear.Areas covered: This narrative review comprehensively examines the clinical utility of the CLZ:NDMC ratio to reduce metabolic risk and increase treatment efficacy. The association of the CLZ:NDMC ratio with changes in psychopathology, cognitive functioning, and cardiometabolic burden will be explored, as well as adjunctive treatments and their effects.Expert opinion: The literature suggests a positive association between the CLZ:NDMC ratio and better cardiometabolic outcomes. Conversely, the CLZ:NDMC ratio appears inversely associated with better cognitive functioning but less consistently with other psychiatric domains. The CLZ:NDMC ratio may be useful for predicting and monitoring cardiometabolic adverse effects and optimizing potential cognitive benefits of clozapine. Future studies are required to replicate these findings, which if substantiated, would encourage examination of adjunctive treatments aiming to alter the CLZ:NDMC ratio to best meet the needs of the individual patient, thereby broadening clozapine's clinical utility.

Insomnia in patients with schizophrenia: current understanding and treatment options

In patients with schizophrenia, insomnia is a common yet often overlooked comorbidity. With sleep disturbances inextricably linked to increased severity of schizophrenia and worsening clinical outcomes, insomnia is an important therapeutic target within this patient population. Thus, through a review of the current literature, this paper reiterates the important etiological link between these two conditions, while evaluating the safety, efficacy, and limitations of current therapeutic options for the treatment of comorbid insomnia in schizophrenia. Despite the continued use of benzodiazepine receptor agonists (BZRAs) for insomnia, the use of other therapies such as Cognitive Behavioral Therapy for Insomnia (CBT-I) and suvorexant warrants increased consideration. More large-scale clinical trials are needed to assess the efficacy of such therapeutic options in the schizophrenia patient population.

Dose-dependent and opposite effects of orexin A on prepulse inhibition response in sleep-deprived and non-sleep-deprived rats

Orexin is a novel neurotransmitter released from lateral hypothalamus, that is a crucial modulator in sleep/wakefulness system. Recent studies also suggest its possible role in the neurodevelopmental disorders, such as schizophrenia. Our study consists of two experiments, where we investigate the effect of orexin A (OXA), one of two isoforms of orexin that can pass blood brain barrier, on the prepulse inhibition of acoustic startle reflex. The first experiment tested the effect of OXA on PPI response of non-sleep-deprived rats via intraperitoneal injection 30min before testing. Our results show that 40μg/kg OXA attenuates PPI% at 78dB and 86dB prepulse intensities. The second experiment utilized 72-h REM sleep deprivation, as a model for sleep-deprivation-induced impairment of PPI response. Here, we tested the effect of OXA on PPI% of sleep-deprived rats via intraperitoneal injection at the last 30min of sleep deprivation, testing for PPI immediately afterwards. Our results showed that (1) sleep deprivation attenuates the PPI% at 74dB, 78dB and 86dB prepulse intensities and (2) 10μg/kg OXA completely restores the impaired PPI% at 78dB only, where the highest PPI% impairment was observed. These results suggest that orexin A modulates PPI response in rats in a dose-dependent manner, oppositely for non-sleep-deprived and sleep-deprived rats, and a more detailed investigation for the etiology of this effect should follow.

Managing interactions between cognitive enhancers and other psychotropics

Polypharmacy is common in psychiatry. Usage of cognitive enhancers is increasing in the psychiatric population. Many clinicians are not familiar with these new psychoactive compounds. This paper reviews the potential drug-drug interactions when these cognitive enhancers are used together with psychotropic drugs and their confounding effects on diagnosis and clinical management.

True alignment of preclinical and clinical research to enhance success in CNS drug development: a review of the current evidence

Central nervous system pharmacological research and development has reached a critical turning point. Patients suffering from disorders afflicting the central nervous system are numerous and command significant attention from the pharmaceutical industry. However, given the numerous failures of promising drugs, many companies are no longer investing in or, indeed, are divesting from this therapeutic area. Central nervous system drug development must change in order to develop effective therapies to treat these patients. Preclinical research is a cornerstone of drug development; however, it is frequently criticised for its lack of predictive validity. Animal models and assays can be shown to be more predictive than reported and, on many occasions, the lack of thorough preclinical testing is potentially to blame for some of the clinical failures. Important factors such as translational aspects, nature of animal models, variances in acute versus chronic dosing, development of add-on therapies and understanding of the full dose-response relationship are too often neglected. Reducing the attrition rate in central nervous system drug development could be achieved by addressing these important questions before novel compounds enter the clinical phase. This review illustrates the relevance of employing these criteria to translational central nervous system research, better to ensure success in developing new drugs in this therapeutic area.

Intractability of Deficit Syndrome of Schizophrenia Against Adjunctive Modafinil

OBJECTIVES

Negative symptoms are a significant barrier to successful functional outcome and recovery in individuals with schizophrenia, and their management is not easy. Prior tryouts with antidepressants and some cognitive enhancers were not really encouraging, and experiments with modafinil had mixed and indecisive results. The objective of the present study was to assess modafinil's efficacy on subjective and objective aspects of negative symptoms of schizophrenia.

METHODS

This study was an 8-week randomized, placebo-controlled trial of modafinil, as an adjective to haloperidol, in treatment of 50 schizophrenic patients. Scale for the Assessment of Negative Symptoms (SANS) was used as the primary outcome measure, and Scale for Assessment of Positive Symptoms, Clinical Global Impressions-Severity Scale, Schedule for Assessment of Insight, Simpson Angus Scale, Psychological General Well-Being Schedule, and Nurses Observation Scale for Inpatient Evaluation were used as secondary measures.

RESULTS

According to the findings, while more cases in the modafinil group (n = 14) showed a positive response in some of the subscales of SANS, in comparison with the placebo group (n = 6; P < 0.04), the intractability of the deficit syndrome of schizophrenia against augmentative modafinil was obvious because there was no significant decrease in the mean total score of SANS in the target group in comparison with the placebo group at the end of the assessment (P < 0.08). In addition, while no significant alteration in most of the secondary measures was evident, a significant improvement in Psychological General Well-Being Schedule (P < 0. 04) and Nurses Observation Scale for Inpatient Evaluation (P < 0. 05) was obvious at the end of the trial.

CONCLUSIONS

According to the results, despite the fact that a remarkable influence by adjunctive modafinil was visible as regards the subjective measures, no significant improvement was evident with respect to deficit syndrome per se.

Motivational activation: a unifying hypothesis of orexin/hypocretin function

Orexins (hypocretins) are two peptides (orexin A and B) produced from the pre-pro-orexin precursor and expressed in a limited region of dorsolateral hypothalamus. Orexins were originally thought to specifically mediate feeding and promote wakefulness, but it is now clear that they participate in a wide range of behavioral and physiological processes under select circumstances. Orexins primarily mediate behavior under situations of high motivational relevance, such as during physiological need states, exposure to threats or reward opportunities. We hypothesize that many behavioral functions of orexins (including regulation of sleep/wake cycling) reflect a fundamentally integrated function for orexins in translating motivational activation into organized suites of psychological and physiological processes supporting adaptive behaviors. We also discuss how numerous forms of neural heterogeneity modulate this function, allowing orexin neurons to organize diverse, adaptive responses in a variety of motivationally relevant situations. Thus, the involvement of orexins in diverse behaviors may reflect a common underlying function for this peptide system.

The use of stimulant medications for non-core aspects of ADHD and in other disorders

Psychostimulants play a central role in the management of ADHD. Here we review the evidence pertaining to the use of methylphenidate, dexamphetamine and related amphetamine salts, the prodrug lisdexamfetamine and modafinil for the management of comorbid ADHD and non-ADHD indications. There is a growing consensus that stimulant medications are helpful at improving the emotional dysregulation and lability, and oppositional and conduct symptoms that are often associated with ADHD. There is some evidence that psychostimulants may improve outcomes in those with treatment resistant depression, reduce negative symptoms and improve cognitive performance in schizophrenia, and that methylphenidate may reduce binge eating in those with bulimia nervosa. In general medicine, whilst the evidence is at times contradictory, psychostimulants have been shown in some studies to be effective treatments for chronic fatigue and narcolepsy, and to improve outcomes post stroke, post head injury, in dementia and various cancers. It seems likely that these effects often result from a combination of, reduction in fatigue, improvements in concentration and cognitive functioning and a lifting of mood which may be a direct or indirect consequence of the medication. Further studies seem warranted and these should focus on efficacy, effectiveness and long term safety. This article is part of the Special Issue entitled 'CNS Stimulants'.

The hypocretin system and psychiatric disorders

The hypocretin system is constituted by a small group of hypothalamic neurons with widespread connections within the entire central nervous system producing two neuropeptides involved in several key physiological functions such as the regulation of sleep and wakefulness, motor control, autonomic functions, metabolism, feeding behavior, and reward. Narcolepsy with cataplexy is a neurological disorder regarded as a disease model for the selective hypocretin system damage, and also shares several psychopatological traits and comorbidities with psychiatric disorders. We reviewed the available literature on the involvement of the hypocretin system in psychiatric nosography. Different evidences such as cerebrospinal hypocretin-1 levels, genetic polymorphisms of the neuropeptides or their receptors, response to treatments, clinical, experimental and functional data directly or indirectly linked the hypocretin system to schizophrenia, mood, anxiety and eating disorders, as well as to addiction. Future genetic and pharmacological studies will disentangle the hypocretin system role in the field of psychiatry.

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.

Assessing the roles of stimulants/stimulant-like drugs and dopamine-agonists in the treatment of bipolar depression

Bipolar depression is considered the most difficult-to-treat phase of bipolar disorder, in relation to its pervasiveness and efficacy and/or tolerability limitations of available treatments. Indeed, most mood stabilizers and atypical antipsychotics are not as effective in ameliorating depressive compared with manic symptoms, and entail substantial tolerability limitations. However, the use of antidepressants is highly controversial, as their efficacy appears less robust in bipolar compared with unipolar depression. In addition, antidepressants, in spite of generally having adequate somatic tolerability, in BD may be associated with a higher risk of manic/hypomanic switch, suicidality and rapid cycling. Among alternative pharmacological strategies, compounds with stimulant and pro-dopaminergic effects, such as methylphenidate, modafinil, armodafinil and pramipexole, have showed potential antidepressant activity, even though their use in clinical practice has been limited by the paucity of controlled evidence. This article seeks to review available evidence about the use of the aforementioned compounds in the treatment of bipolar depression. Findings from reviewed studies suggested that pro-dopaminergic compounds, such as pramipexole and stimulants/stimulant-like agents, deserve consideration as adjunctive therapies in bipolar depressed patients, at least in some subgroups of patients. Nevertheless, caution regarding their use is recommended as further clinical trials with larger samples and longer follow-up periods are necessary to clarify the roles of these medications in bipolar depression.

Cognitive enhancement in schizophrenia: pharmacological and cognitive remediation approaches

This article discusses the measurement of cognition in schizophrenia, its role as a determinant of disability, and treatment efforts to date, including pharmacological and behavioral interventions as well as effective treatments that lead to improved outcomes. The measurement of functioning when patients with schizophrenia receive treatment in the office is addressed. The review focuses on new developments in the creation and adoption of a consensus method for the assessment of cognitive functioning in treatment studies, on the increased appreciation for assessment of functional skills in the prediction of everyday outcomes, and on developments in the basic neuroscience of cognition.

Modafinil effects on cognition and emotion in schizophrenia and its neurochemical modulation in the brain

Modafinil is a central nervous system wake promoting agent used for the treatment of excessive daytime sleeping. Its vigilance promoting properties and low abuse potential has intrigued the scientific community and has led to use it as a cognitive enhancer, before its neural functions were understood. Here, we review the effects of modafinil in human cognition and emotion and its specific actions on symptoms in patients with schizophrenia and whether these are consistently effective throughout the literature. We also performed a systematic review on the effects of modafinil on neurotransmitter signalling in different areas of the brain in order to better understand the neuromechanisms of its cognitive and emotional enhancing properties. A review of its effects in schizophrenia suggests that modafinil facilitates cognitive functions, with pro-mnemonic effects and problem solving improvements. Emotional processing also appears to be enhanced by the drug, although to date there are only a limited number of studies. The systematic review on the neurochemical modulation of the modafinil suggests that its mnemonic enhancing properties might be the result of glutamatergic and dopaminergic increased neuronal activation in the hippocampus and in the prefrontal cortex respectively. Other neurotransmitters were also activated by modafinil in various limbic brain areas, suggesting that the drug acts on these brain regions to influence emotional responses. These reviews seek to delineate the neuronal mechanisms by which modafinil affects cognitive and emotional function. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

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.

Antipsychotic-induced somnolence in mothers with schizophrenia

Although it is known that many antipsychotic drugs, at the doses prescribed for schizophrenia, are sedative and cause daytime drowsiness, the effect of potentially diminished vigilance on parenting parameters has not been studied. The aim of this paper is to advise clinicians about sedative load in mothers who are prescribed antipsychotic medication. A Medline search was conducted into the sedative effects of antipsychotics, with the following search terms: sleep; sedation; somnolence; wakefulness; antipsychotics; schizophrenia, parenting, maternal behavior, and custody. The results showed that antipsychotic drugs differ in their propensity to induce sedation and do so via their effects on a variety of neurotransmitter systems. It is important to note that mothers with schizophrenia risk losing custody of their infants if they are perceived as potentially neglectful because of excessive daytime sleepiness. Clinicians must choose antipsychotic medications carefully and monitor for sedative effects whenever the patient has important responsibilities that require the maintenance of vigilance.

fMRI working memory hypo-activations in schizophrenia come with a coupling deficit between arousal and cognition

Cognition has become a target for therapeutic intervention and favoring arousal could be a way to help patients. Working memory is an arousal dependent cognitive function. This study used functional MRI (fMRI) as a surrogate marker of working memory to evaluate the sensitivity of patients' hypoactive regions to arousal in a subpopulation of rehabilitated patients. Are hypoactive regions sensitive to arousal? Does the deficit result from arousal deficit or improper coupling with cognitive activity? Eighteen patients and matched controls were recruited. Participants performed a working memory task during combined electroencephalographic (EEG) and fMRI measurements. Cortical regions sensitive to arousal were defined as those which were inversely correlated with low EEG frequencies. Overlap between the arousal-sensitive and hypoactive regions was assessed by mutual information. Arousal-cognitive coupling was evaluated by the correlation between the arousal effect and the task effect. In the patient group, most hypoactive voxels were sensitive to arousal and corresponded to the prefronto-parietal network. But patients had no arousal deficit. Although arousal seems to improve cognitive activity in most of the patients' cortical areas, this coupling appears to be specifically disturbed in their hypoactive regions. In conclusion, although increasing arousal may help cognition, it may do so in an unspecific way.

Khat chewing in persons with severe mental illness in Ethiopia: a qualitative study exploring perspectives of patients and caregivers

People with severe mental illness (SMI) in Ethiopia chew khat despite advice from their physicians to desist. We wanted to better understand their reasons for khat chewing, including any benefits that they might gain. A qualitative study was conducted involving patients with SMI and their caregivers in Butajira. Reasons given by patients as well as caregivers were more or less congruent: social pressure, a means for survival by improving function, combating medication side effects, to experience pleasure and curbing appetite. These findings will be of value to health workers, caregivers and policymakers alike in improving care and understanding for this patient group. Furthermore, our study indicates a role for future research to explore potentially beneficial effects of khat in this population.

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.

Evidence-based guidelines for the pharmacological treatment of schizophrenia: recommendations from the British Association for Psychopharmacology

These guidelines from the British Association for Psychopharmacology address the scope and targets of pharmacological treatment for schizophrenia. A consensus meeting, involving experts in schizophrenia and its treatment, reviewed key areas and considered the strength of evidence and clinical implications. The guidelines were drawn up after extensive feedback from the participants and interested parties, and cover the pharmacological management and treatment of schizophrenia across the various stages of the illness, including first-episode, relapse prevention, and illness that has proved refractory to standard treatment. The practice recommendations presented are based on the available evidence to date, and seek to clarify which interventions are of proven benefit. It is hoped that the recommendations will help to inform clinical decision making for practitioners, and perhaps also serve as a source of information for patients and carers. They are accompanied by a more detailed qualitative review of the available evidence. The strength of supporting evidence for each recommendation is rated.

Opposite roles of dopamine and orexin in quinpirole-induced excessive drinking: a rat model of psychotic polydipsia

RATIONALE

Repeated administration of the dopamine D2/D3 agonist quinpirole (QNP) progressively increases non-regulatory water intake. This effect may model psychotic polydipsia, a potentially fatal but poorly understood condition.

OBJECTIVES

The growing evidence for a role of orexin in mediating arousal and cognition has linked this peptide to schizophrenia, hence we examined whether manipulations of dopaminergic and orexinergic systems, as well as of setting, would further characterize the model.

METHODS

Water intake was measured in rats sequentially tested in home and then operant conditioning setting, with chronic administration of D2 antagonist haloperidol (Hal) prior to QNP treatment. A group of rats similarly treated was also assessed for orexin A (OxA) expression in the cortex. Finally, the effect of the orexin-1 receptor antagonist SB-334867 on QNP-induced polydipsia was evaluated.

RESULTS

In rats made polydipsic by QNP the amount of water drank during the first 4 h was strongly correlated with the degree of dissociation between appetitive and consummatory components of drinking behavior in the following hour of operant access to water. Hal 0.2 mg/kg prevented both polydipsia and the dissociation, while 0.1 mg/kg only blocked the dissociation. Chronic QNP treatment increased, in a Hal-reversible way, OxA expression in the somatosensory cortex (SI). Moreover, pretreatment with SB-334867 sped up and potentiated QNP-induced polydipsia.

CONCLUSIONS

Results disclose compulsive components in QNP-induced polydipsia that are mediated by dopamine D2 receptors. QNP also regulates OxA expression in the SI, while the block of orexin-1 receptors enhances QNP-induced polydipsia. We suggest that dopamine and OxA play opposite roles in QNP-induced polydipsia.

Pharmacological strategies for enhancing cognition in schizophrenia

Researchers have long recognized that individuals with schizophrenia experience challenges in a wide range of cognitive domains, and research on cognitive impairment in schizophrenia is not a recent phenomena. However, the past 10-20 years have seen an increasing recognition of the central importance of cognition to understanding function and outcome in this illness (Green et al. in Schizophr Bull 26:119-136, 2000), an awareness that has shifted the emphasis of at least some work on schizophrenia. More specifically, there has been a rapidly growing body of work on methods of enhancing cognition in schizophrenia, as a means to potentially facilitate improved outcome and quality of life for individuals with this debilitating illness. The current chapter reviews the results of a range of studies examining adjunctive pharmacological treatments to enhance cognition in schizophrenia using a range of designs, including single-dose studies, open-label repeated dosing studies, and double-blind parallel group and crossover designs with repeated dosing. Although many of the single-dose and open-label studies have suggested positive cognitive effects from a range of agents, few of the larger-scale double-blind studies have generated positive results. The current state of results may reflect the need to identify alternative molecular mechanisms for enhancing cognition in schizophrenia or the need to reconceptualize the ways in which pharmacological agents may improve cognition in this illness, with a concomitant change in the traditional clinical trial study design used in prior studies of cognitive enhancement in schizophrenia.

Translational Aspects of the Novel Object Recognition Task in Rats Abstinent Following Sub-Chronic Treatment with Phencyclidine (PCP): Effects of Modafinil and Relevance to Cognitive Deficits in Schizophrenia

Phencyclidine (PCP) induces a behavioral syndrome in rodents that bears remarkable similarities to some of the core symptoms observed in schizophrenic patients, among those cognitive deficits. The successful alleviation of cognitive impairments associated with schizophrenia (CIAS) has become a major focus of research efforts as they remain largely untreated. The aim of the present study was to investigate the effects of selected antipsychotic and cognition enhancing drugs, namely haloperidol, risperidone, donepezil, and modafinil in an animal model widely used in preclinical schizophrenia research. To this end, the novel object recognition (NOR) task was applied to rats abstinent following sub-chronic treatment with PCP. Rats were administered either PCP (5 mg/kg, i.p.) or vehicle twice a day for 7 days, followed by a 7-day washout period, before testing in NOR. Upon testing, vehicle-treated rats successfully discriminated between novel and familiar objects, an effect abolished in rats that had previously been exposed to PCP treatment. Acute treatment with modafinil (64 mg/kg, p.o.) ameliorated the PCP-induced deficit in novel object exploration, whereas haloperidol (0.1 mg/kg, s.c.), risperidone (0.2 mg/kg, i.p.), and donepezil (3 mg/kg, p.o.) were without significant effect. Given the negligible efficacy of haloperidol and risperidone, and the contradictory data with donepezil to treat CIAS in the clinic, together with the promising preliminary pro-cognitive effects of modafinil in certain subsets of schizophrenic patients, the sub-chronic PCP-NOR abstinence paradigm may represent an attractive option for the identification of potential novel treatments for CIAS.

Pharmacological cognitive enhancement in schizophrenia

Cognitive impairments in schizophrenia are common and severe. These impairments are also related to functional disability in schizophrenia. As a result, efforts are underway to enhance cognition in schizophrenia through a variety of pharmacological mechanisms. As part of this effort, a designated research design has been developed for this process, through an extensive consensus and validation effort. This paper reviews the methods for pharmacological cognitive enhancement, as well as previous results of efforts in the pharmacological domains. These domains include cholinergic, noradrenergic, serotonergic, glutamatergic, and GABA-ergic mechanisms. While previous results have not been particularly encouraging, there are many challenges that need to be overcome and many of the reasons for past failures may be due to resolvable issues. It is likely that this will be an area of research that will be developing extensively over the next decade and expanding to other conditions as well.

Recent advances in treating cognitive impairment in schizophrenia

INTRODUCTION

Schizophrenia is often associated with chronic disability and poor outcome. In addition to positive symptoms, such as hallucinations and delusions, and negative symptoms including poverty of speech and blunted affect, schizophrenia is also associated with deficits in cognitive function. It has been increasingly recognized that the severity of cognitive impairment is a major determinant of outcome. Therefore, interventions to improve cognitive function also have the capacity to improve quality of life and social and occupational outcomes. Whilst some of the antipsychotic drugs have shown some selective benefits, there is some controversy about the extent of these benefits.

OBJECTIVES

This article provides an overview of research into drugs that might enhance cognition in schizophrenia.

CONCLUSION

Drugs such as modafanil and galantamine are being evaluated, and a number of new drugs are currently in development. Standardized cognitive assessment measures are being developed so studies can be compared more easily. This field is advancing rapidly, but as yet, no widely applicable, evidence-based treatments are available to the clinician.

Comparison of haloperidol, risperidone, sertindole, and modafinil to reverse an attentional set-shifting impairment following subchronic PCP administration in the rat--a back translational study

RATIONALE

Selective cognitive impairments, including those of executive function as assessed using the Wisconsin Card Sort Test or intradimensional-extradimensional (ID-ED) tests, are a key feature of schizophrenia but remain inadequately treated by existing therapies. Recently, however, modafinil has been shown to improve attentional set-shifting performance in patients with schizophrenia.

OBJECTIVE

The present study evaluated the recently described analogous rat ID-ED attentional set-shifting task by investigating the effects of various pharmacological challenges to a phencyclidine (PCP)-induced ED shift impairment, namely, haloperidol, risperidone, sertindole, and modafinil.

MATERIALS AND METHODS

Rats were subjected to a subchronic systemic administration of either saline vehicle or PCP (5 mg/kg i.p. b.i.d. for 7 days) followed by a 7-day washout period. During this period, rats were trained to dig in baited bowls for a food reward and to discriminate based on odor or digging media. In a single test session conducted the day after the washout period (day 8), rats performed a series of discriminations following acute administration of either vehicle, or haloperidol (0.1 mg/kg s.c.), or risperidone (0.2 mg/kg i.p.), or sertindole (1.25 mg/kg p.o.) or modafinil (64 mg/kg p.o.).

RESULTS

The subchronic PCP-induced ED deficit was ameliorated by sertindole and modafinil but not by haloperidol or risperidone.

CONCLUSIONS

Overall, these findings further support that the rat ID-ED test in subchronic PCP-treated rats has utility and validity as a preclinical model of the cognitive symptoms of schizophrenia and demonstrates back-translational potential.

Asenapine restores cognitive flexibility in rats with medial prefrontal cortex lesions

RATIONALE

Cognitive inflexibility in schizophrenia is treatment-resistant and predictive of poor outcome. This study examined the effect of asenapine, a novel psychopharmacologic agent being developed for schizophrenia and bipolar disorder, on cognitive dysfunction in the rat.

OBJECTIVES

The objective of this paper was to establish whether asenapine has a beneficial effect on the performance of rats with ibotenic acid-induced lesion of the medial prefrontal cortex (mPFC) in an intradimensional/extradimensional (ID/ED) test of cognitive flexibility.

METHODS

The effect of subcutaneously administered asenapine (0.75, 7.5, 75 microg/kg) on ID/ED performance of controls or mPFC-lesioned rats was examined using a within-subjects, repeated-measures design. In a second experiment, lesioned and control rats were tested with or without asenapine in a modified version of the task, with multiple set-shifts, before brains were processed for Fos-immunoreactivity in the mPFC.

RESULTS

The mPFC lesion-induced deficit in the ID/ED task was stable with repeated testing over more than two months. Asenapine (75 microg/kg s.c., p < 0.05) completely restored the performance of lesioned rats. Experiment 2 replicated both lesion and asenapine effects and demonstrated that it is possible to measure set-shifting multiple times within a test session. Asenapine (75 microg/kg s.c.) was associated with differential activation of the neurons in the anterior mPFC of lesioned animals, but was without effect in controls.

CONCLUSION

Asenapine can ameliorate mPFC lesion-induced impairment in attentional set-shifting, and is associated with a greater activation of the spared neurons in the anterior mPFC. These data suggest that asenapine may benefit impaired cognitive flexibility in disorders such as schizophrenia.