High-dose galantamine augmentation inferior to placebo on attention, inhibitory control and working memory performance in nonsmokers with schizophrenia

Cholinergic Functioning, Cognition, and Anticholinergic Medication Burden in Schizophrenia

Acetylcholine (ACh) signaling is critical for central nervous function and is known to be abnormal in schizophrenia (SZ), a chronic neuropsychiatric disorder in which cognitive deficits persist, despite treatment. This review provides a summary of the clinical evidence linking ACh abnormalities to SZ-associated cognitive deficits, an overview of ACh-based pro-cognitive strategies attempted in SZ, and a survey of recent studies that describe the impact of anticholinergic medication burden on cognitive outcomes in SZ. Methodological challenges that currently limit more substantial investigation of ACh in SZ patients and future directions are also discussed.

The effects of galangin in prepulse inhibition test and experimental schizophrenia models

OBJECTIVE

Acetylcholinesterase inhibitors are the focus of interest in the management of schizophrenia. We aimed to investigate the effects of acute galangin administration, a flavonoid compound with acetylcholinesterase inhibiting activity, on schizophrenia-associated cognitive deficits in rats and schizophrenia models in mice.

METHODS

Apomorphine-induced prepulse inhibition (PPI) disruption for cognitive functions, nicotinic, muscarinic, and serotonergic mechanism involvement, and brain acetylcholine levels were investigated in Wistar rats. Apomorphine-induced climbing, MK-801-induced hyperlocomotion, and catalepsy tests were used as schizophrenia models in Swiss albino mice. The effects of galangin were compared with acetylcholinesterase inhibitor donepezil, and typical and atypical antipsychotics haloperidol and olanzapine, respectively.

RESULTS

Galangin (50,100 mg/kg) enhanced apomorphine-induced PPI disruption similar to donepezil, haloperidol, and olanzapine (p < 0.05). This effect was not altered in the combination of galangin with the nicotinic receptor antagonist mecamylamine (1 mg/kg), the muscarinic receptor antagonist scopolamine (0.05 mg/kg), or the serotonin-1A receptor antagonist WAY-100635 (1 mg/kg) (p > 0.05). Galangin (50,100 mg/kg) alone increased brain acetylcholine concentrations (p < 0.05), but not in apomorphine-injected rats (p > 0.05). Galangin (50 mg/kg) decreased apomorphine-induced climbing and MK-801-induced hyperlocomotion similar to haloperidol and olanzapine (p < 0.05), but did not induce catalepsy, unlike them.

CONCLUSION

We suggest that galangin may help enhance schizophrenia-associated cognitive deficits, and nicotinic, muscarinic cholinergic, and serotonin-1A receptors are not involved in this effect. Galangin also exerted an antipsychotic-like effect without inducing catalepsy and may be considered as an advantageous antipsychotic agent.

The Role of G Protein-Coupled Receptors (GPCRs) and Calcium Signaling in Schizophrenia. Focus on GPCRs Activated by Neurotransmitters and Chemokines

Schizophrenia is a common debilitating disease characterized by continuous or relapsing episodes of psychosis. Although the molecular mechanisms underlying this psychiatric illness remain incompletely understood, a growing body of clinical, pharmacological, and genetic evidence suggests that G protein-coupled receptors (GPCRs) play a critical role in disease development, progression, and treatment. This pivotal role is further highlighted by the fact that GPCRs are the most common targets for antipsychotic drugs. The GPCRs activation evokes slow synaptic transmission through several downstream pathways, many of them engaging intracellular Ca²⁺ mobilization. Dysfunctions of the neurotransmitter systems involving the action of GPCRs in the frontal and limbic-related regions are likely to underly the complex picture that includes the whole spectrum of positive and negative schizophrenia symptoms. Therefore, the progress in our understanding of GPCRs function in the control of brain cognitive functions is expected to open new avenues for selective drug development. In this paper, we review and synthesize the recent data regarding the contribution of neurotransmitter-GPCRs signaling to schizophrenia symptomology.

Treating disorders across the lifespan by modulating cholinergic signaling with galantamine

Advances in understanding the regulatory functions of the nervous system have revealed neural cholinergic signaling as a key regulator of cytokine responses and inflammation. Cholinergic drugs, including the centrally acting acetylcholinesterase inhibitor, galantamine, which are in clinical use for the treatment of Alzheimer's disease and other neurodegenerative and neuropsychiatric disorders, have been rediscovered as anti-inflammatory agents. Here, we provide a timely update on this active research and clinical developments. We summarize the involvement of cholinergic mechanisms and inflammation in the pathobiology of Alzheimer's disease, Parkinson's disease, and schizophrenia, and the effectiveness of galantamine treatment. We also highlight recent findings demonstrating the effects of galantamine in preclinical and clinical settings of numerous conditions and diseases across the lifespan that are characterized by immunological, neurological, and metabolic dysfunction.

Boosting the autophagy-lysosomal pathway by phytochemicals: A potential therapeutic strategy against Alzheimer's disease

The lysosome is a membrane-enclosed organelle in eukaryotic cells, which has basic pattern recognition for nutrient-dependent signal transduction. In Alzheimer's disease, the already declining autophagy-lysosomal function is exacerbated by an increased need for clearance of damaged proteins and organelles in aged cells. Recent evidence suggests that numerous diseases are linked to impaired autophagy upstream of lysosomes. In this way, a comprehensive survey on the pathophysiology of the disease seems necessary. Hence, in the first section of this review, we will discuss the ultimate findings in lysosomal signaling functions and how they affect cellular metabolism and trafficking under neurodegenerative conditions, specifically Alzheimer's disease. In the second section, we focus on how natural products and their derivatives are involved in the regulation of inflammation and lysosomal dysfunction pathways, including how these should be considered a crucial target for Alzheimer's disease therapeutics.

Meta-analysis of randomized controlled trials of galantamine in schizophrenia: significant cognitive enhancement

Cognitive impairments are core features of schizophrenia and the best predictor of functional outcome. Cholinergic system and alpha-7 nicotinic acetylcholine (α7nACh) receptors are strongly implicated in the pathophysiologic mechanisms associated with cognitive impairments in schizophrenia. Galantamine is not only a reversible, competitive inhibitor of acetylcholinesterase but also a type I positive allosteric modulator of α7nACh receptors. The objective of this meta-analysis was to examine the efficacy of galantamine for cognitive symptoms of schizophrenia. In the meta-analysis that included six randomized controlled trials (RCTs, N=226), cognitive impairments significantly improved with galantamine compared to placebo, with a small Hedges' g effect size of 0.233. This finding is consistent with other RCTs in schizophrenia with medications with a similar mechanism of action. On the basis of the results from all the failed (although some efficacy has been shown) RCTs to date in schizophrenia, targeting only one pathophysiologic mechanism may be insufficient to detect a clinically meaningful signal. Nicotinergic medications, like any other add-on medications, are unlikely to be effective as stand-alone medications. Hence, these medications may have to be combined with other medications with complementary mechanisms such as glutamatergic/N-methyl-D-aspartate systems to detect a meaningful effect size for the three domains of psychopathology.

Computational Dissociation of Dopaminergic and Cholinergic Effects on Action Selection and Inhibitory Control

BACKGROUND

Patients with schizophrenia make more errors than healthy subjects in the antisaccade task. In this paradigm, participants are required to inhibit a reflexive saccade to a target and to select the correct action (a saccade in the opposite direction). While the precise origin of this deficit is not clear, it has been connected to aberrant dopaminergic and cholinergic neuromodulation.

METHODS

To study the impact of dopamine and acetylcholine on inhibitory control and action selection, we administered two selective drugs (levodopa 200 mg/galantamine 8 mg) to healthy volunteers (N = 100) performing the antisaccade task. The computational model SERIA (stochastic early reaction, inhibition, and late action) was employed to separate the contribution of inhibitory control and action selection to empirical reaction times and error rates.

RESULTS

Modeling suggested that levodopa improved action selection (at the cost of increased reaction times) but did not have a significant effect on inhibitory control. By contrast, according to our model, galantamine affected inhibitory control in a dose-dependent fashion, reducing inhibition failures at low doses and increasing them at higher levels. These effects were sufficiently specific that the computational analysis allowed for identifying the drug administered to an individual with 70% accuracy.

CONCLUSIONS

Our results do not support the hypothesis that elevated tonic dopamine strongly impairs inhibitory control. Rather, levodopa improved the ability to select correct actions. However, inhibitory control was modulated by cholinergic drugs. This approach may provide a starting point for future computational assays that differentiate neuromodulatory abnormalities in heterogeneous diseases like schizophrenia.

The past and future of novel, non-dopamine-2 receptor therapeutics for schizophrenia: A critical and comprehensive review

Since the discovery of chlorpromazine in the 1950's, antipsychotic drugs have been the cornerstone of treatment of schizophrenia, and all attenuate dopamine transmission at the dopamine-2 receptor. Drug development for schizophrenia since that time has led to improvements in side effects and tolerability, and limited improvements in efficacy, with the exception of clozapine. However, the reasons for clozapine's greater efficacy remain unclear, despite the great efforts and resources invested therewith. We performed a comprehensive review of the literature to determine the fate of previously tested, non-dopamine-2 receptor experimental treatments. Overall we included 250 studies in the review from the period 1970 to 2017 including treatments with glutamatergic, serotonergic, cholinergic, neuropeptidergic, hormone-based, dopaminergic, metabolic, vitamin/naturopathic, histaminergic, infection/inflammation-based, and miscellaneous mechanisms. Despite there being several promising targets, such as allosteric modulation of the NMDA and α7 nicotinic receptors, we cannot confidently state that any of the mechanistically novel experimental treatments covered in this review are definitely effective for the treatment of schizophrenia and ready for clinical use. We discuss potential reasons for the relative lack of progress in developing non-dopamine-2 receptor treatments for schizophrenia and provide recommendations for future efforts pursuing novel drug development for schizophrenia.

Potential Role of Antipsychotic-Galantamine-Memantine Combination in the Treatment of Positive, Cognitive, and Negative Symptoms of Schizophrenia

Schizophrenia is, in part, a cognitive illness. There are no approved medications for cognitive impairments associated with schizophrenia (CIAS) and primary negative symptoms. Cholinergic and glutamatergic systems, alpha-7 nicotinic acetylcholine (α-7nACh) and N-methyl-D-aspartate (NMDA) receptors, kynurenic acid (KYNA), and mismatch negativity have been implicated in the pathophysiology of CIAS and negative symptoms. Galantamine is an acetylcholinesterase inhibitor that is also a positive allosteric modulator at the α4β2 and α7nACh receptors. Memantine is a noncompetitive NMDA receptor antagonist. Galantamine and memantine alone and in combination were effective for cognition in animals and people with Alzheimer's disease. The objective of this article is to critically dissect the published randomized controlled trials with galantamine and memantine for CIAS to highlight the efficacy signal. These studies may have failed to detect a clinically meaningful efficacy signal due to limitations, methodological issues, and possible medication nonadherence. There is evidence from a small open-label study that the galantamine-memantine combination may be effective for CIAS with kynurenine pathway metabolites as biomarkers to detect the severity of cognitive impairments. Given that there are no available treatments for cognitive impairments and primary negative symptoms in schizophrenia, testing of this "five-pronged strategy" (quintuple hypotheses: dopamine, nicotinic-cholinergic, glutamatergic/NMDA, GABA, and KYNA) is a "low-risk high-gain" approach that could be a major breakthrough in the field. The galantamine-memantine combination has the potential to treat positive, cognitive, and negative symptoms, and targeting the quintuple hypotheses concurrently may lead to a major scientific advancement - from antipsychotic treatment to antischizophrenia treatment.

Cognitive improvement of acetylcholinesterase inhibitors in schizophrenia

BACKGROUND

Schizophrenia is a severe, persistent mental disorder, and a leading cause of disability worldwide. Cognitive impairments presented in schizophrenia lead to a worse prognostic, thus treatments targeted to enhance cognition in schizophrenia may be clinically relevant.

AIMS

The purpose of this study was to assess the efficacy of acetylcholinesterase inhibitors as add-on medication to antipsychotics on cognition in patients with schizophrenia.

METHODS

Search strategies were developed for Medline, Embase and Cochrane Central Register of Controlled Trials, and are current to March 2018. We included randomised controlled trials that compared antipsychotics plus acetylcholinesterase inhibitors versus antipsychotics plus placebo on prespecified cognitive domains (speed of processing, attention and working memory). Two review authors independently evaluated study eligibility, extracted data and assessed the risk of bias of included studies. We used random-effects model for meta-analyses and assessed the quality of evidence using Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

We included nine randomised controlled trials. Six randomised controlled trials ( n=219) presented evidence that acetylcholinesterase inhibitors improve speed of processing (standardised mean difference -0.52, 95% confidence interval (-0.79 to -0.25); p value=0.0002). However, eight randomised controlled trials ( n=252) did find placebo was better than acetylcholinesterase inhibitors in the attention domain (-0.43, (-0.72 to -0.13); p value=0.005) and eight randomised controlled trials ( n=273) did not find differences in the working memory (-0.14, (-0.51 to 0.24), p value=0.47).

CONCLUSIONS

The current evidence is too weak to base recommendations on the use of acetylcholinesterase inhibitors as adjunctive treatments to antipsychotics to improve basic cognitive functions. We have limited confidence in the effect estimates.

Efficacy of different types of cognitive enhancers for patients with schizophrenia: a meta-analysis

Cognitive impairment is a core feature of schizophrenia, which is predictive for functional outcomes and is, therefore, a treatment target in itself. Yet, literature on efficacy of different pharmaco-therapeutic options is inconsistent. This quantitative review provides an overview of studies that investigated potential cognitive enhancers in schizophrenia. We included pharmacological agents, which target different neurotransmitter systems and evaluated their efficacy on overall cognitive functioning and seven separate cognitive domains. In total, 93 studies with 5630 patients were included. Cognitive enhancers, when combined across all different neurotransmitter systems, which act on a large number of different mechanisms, showed a significant (yet small) positive effect size of 0.10 (k = 51, p = 0.023; 95% CI = 0.01 to 0.18) on overall cognition. Cognitive enhancers were not superior to placebo for separate cognitive domains. When analyzing each neurotransmitter system separately, agents acting predominantly on the glutamatergic system showed a small significant effect on overall cognition (k = 29, Hedges’ g = 0.19, p = 0.01), as well as on working memory (k = 20, Hedges’ g = 0.13, p = 0.04). A sub-analysis of cholinesterase inhibitors (ChEI) showed a small effect on working memory (k = 6, Hedges’ g = 0.26, p = 0.03). Other sub-analyses were positively nonsignificant, which may partly be due to the low number of studies we could include per neurotransmitter system. Overall, this meta-analysis showed few favorable effects of cognitive enhancers for patients with schizophrenia, partly due to lack of power. There is a lack of studies involving agents acting on other than glutamatergic and cholinergic systems, especially of those targeting the dopaminergic system.

Medications Used for Cognitive Enhancement in Patients With Schizophrenia, Bipolar Disorder, Alzheimer's Disease, and Parkinson's Disease

BACKGROUND/AIMS

Cognitive impairment, which frequently occurs in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease, has a significant impact on the daily lives of both patients and their family. Furthermore, since the medications used for cognitive enhancement have limited efficacy, the issue of cognitive enhancement still remains a clinically unsolved challenge.

SAMPLING AND METHODS

We reviewed the clinical studies (published between 2007 and 2017) that focused on the efficacy of medications used for enhancing cognition in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease.

RESULTS

Acetylcholinesterase inhibitors and memantine are the standard treatments for Alzheimer's disease and Parkinson's disease. Some studies have reported selective cognitive improvement in patients with schizophrenia following galantamine treatment. Newer antipsychotics, including paliperidone, lurasidone, aripiprazole, ziprasidone, and BL-1020, have also been reported to exert cognitive benefits in patients with schizophrenia. Dopaminergic medications were found to improve language function in patients with Parkinson's disease. However, no beneficial effects on cognitive function were observed with dopamine agonists in patients with schizophrenia. The efficacies of nicotine and its receptor modulators in cognitive improvement remain controversial, with the majority of studies showing that varenicline significantly improved the cognitive function in schizophrenic patients. Several studies have reported that N-methyl-d-aspartate glutamate receptor (NMDAR) enhancers improved the cognitive function in patients with chronic schizophrenia. NMDAR enhancers might also have cognitive benefits in patients with Alzheimer's disease or Parkinson's disease. Raloxifene, a selective estrogen receptor modulator, has also been demonstrated to have beneficial effects on attention, processing speed, and memory in female patients with schizophrenia.

CONCLUSION

Clinical trials with larger sample sizes evaluating comprehensive cognitive domains are warranted to examine the efficacy of medications in cognitive enhancement in patients with schizophrenia, bipolar disorder, Alzheimer's disease, and Parkinson's disease.

A Randomized Clinical Trial of Oxytocin or Galantamine for the Treatment of Negative Symptoms and Cognitive Impairments in People With Schizophrenia

PURPOSE/BACKGROUND

Negative symptoms and cognitive impairments tend to co-occur in people with schizophrenia. If their association with each other is due, in part, to shared pathophysiology, then this suggests that a single drug could potentially be effective for both domains. The current study was designed to examine this hypothesis.

METHODS/PROCEDURES

Fifty-eight participants with either Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision schizophrenia or schizoaffective disorder entered into a 6-week double-blind, placebo-controlled, double-dummy, randomized clinical trial of intranasal oxytocin and galantamine. Seventeen participants were randomized to intranasal oxytocin, 20 were randomized to galantamine, and 21 were randomized to placebo. The Scale for the Assessment of Negative Symptoms total score was used to assess change in negative symptoms (the primary outcome measure for oxytocin). The MATRICS Consensus Cognitive Battery composite score was used to assess cognition (the primary outcome measure for galantamine).

FINDINGS/RESULTS

There were no significant group differences for negative symptoms (oxytocin vs placebo: F2,47.4 = 0.19, P = 0.83; galantamine vs placebo: F2,52.5 = 0.41, P = 0.67). There were no significant group differences for cognitive impairments (galantamine vs placebo: t40 = 0.71, P = 0.48; oxytocin vs placebo: t40 = 0.50, P = 0.62). There were also no significant group differences for the functional capacity or ancillary symptom measures.

IMPLICATIONS/CONCLUSIONS

The lack of an efficacy signal for either compound precluded our ability to test whether pharmacological treatment pathways for negative symptoms and cognitive impairments overlap or are independent.

Cognitive Function as a Transdiagnostic Treatment Target in Stimulant Use Disorders

Stimulant use disorder is an important public health problem, with an estimated 2.1 million current users in the United States alone. No pharmacological treatments are approved by the U.S. Food and Drug Administration for stimulant use disorder and behavioral treatments have variable efficacy and limited availability. Most individuals with stimulant use disorder have other comorbidities, most with overlapping symptoms and cognitive impairments. The goal of this article is to present a rationale for cognition as a treatment target in stimulant use disorder and to outline potential treatment approaches. Rates of lifetime comorbid psychiatric disorders among people with stimulant use disorders are estimated at 65% to 73%, with the most common being mood disorders (13% to 64%) and anxiety disorders (21% to 50%), as well as non-substance-induced psychotic disorders (<10%). There are several models of addictive behavior, but the dual process model particularly highlights the relevance of cognitive impairments and biases to the development and maintenance of addiction. This model explains addictive behavior as a balance between automatic processes and executive control, which in turn are related to individual (genetics, comorbid disorders, psychosocial factors) and other (craving, triggers, drug use) factors. Certain cognitive impairments, such as attentional bias and approach bias, are most relevant to automatic processes, while sustained attention, response inhibition, and working memory are primarily related to executive control. These cognitive impairments and biases are also common in disorders frequently comorbid with stimulant use disorder and predict poor treatment retention and clinical outcomes. As such, they may serve as feasible transdiagnostic treatment targets. There are promising pharmacological, cognitive, and behavioral approaches that aim to enhance cognitive function. Pharmacotherapies target cognitive impairments associated with executive control and include cholinesterase inhibitors (e.g., galantamine, rivastigmine) and monoamine transporter inhibitors (e.g., modafinil, methylphenidate). Cognitive behavioral therapy and cognitive rehabilitation also enhance executive control, while cognitive bias modification targets impairments associated with automatic processes. Cognitive enhancement to improve treatment outcomes is a novel and promising strategy, but its clinical value for the treatment of stimulant use disorder, with or without other psychiatric comorbidities, remains to be determined in future studies.

Assessing the synergy between cholinomimetics and memantine as augmentation therapy in cognitive impairment in schizophrenia. A virtual human patient trial using quantitative systems pharmacology

While many drug discovery research programs aim to develop highly selective clinical candidates, their clinical success is limited because of the complex non-linear interactions of human brain neuronal circuits. Therefore, a rational approach for identifying appropriate synergistic multipharmacology and validating optimal target combinations is desperately needed. A mechanism-based Quantitative Systems Pharmacology (QSP) computer-based modeling platform that combines biophysically realistic preclinical neurophysiology and neuropharmacology with clinical information is a possible solution. This paper reports the application of such a model for Cognitive Impairment In Schizophrenia (CIAS), where the cholinomimetics galantamine and donepezil are combined with memantine and with different antipsychotics and smoking in a virtual human patient experiment. The results suggest that cholinomimetics added to antipsychotics have a modest effect on cognition in CIAS in non-smoking patients with haloperidol and risperidone and to a lesser extent with olanzapine and aripiprazole. Smoking reduces the effect of cholinomimetics with aripiprazole and olanzapine, but enhances the effect in haloperidol and risperidone. Adding memantine to antipsychotics improves cognition except with quetiapine, an effect enhanced with smoking. Combining cholinomimetics, antipsychotics and memantine in general shows an additive effect, except for a negative interaction with aripiprazole and quetiapine and a synergistic effect with olanzapine and haloperidol in non-smokers and haloperidol in smokers. The complex interaction of cholinomimetics with memantine, antipsychotics and smoking can be quantitatively studied using mechanism-based advanced computer modeling. QSP modeling of virtual human patients can possibly generate useful insights on the non-linear interactions of multipharmacology drugs and support complex CNS R&D projects in cognition in search of synergistic polypharmacy.

Drug repurposing and emerging adjunctive treatments for schizophrenia

INTRODUCTION

Schizophrenia is a frequent disorder, which substantially impairs patients' quality of life. Moreover, the burden of illness for patients, their families and for the society, in general, is substantial. Nevertheless, the understanding of the pathophysiology of this syndrome, concise diagnostic methods and more effective and tolerable treatments are still lacking. Thus, innovative approaches and the exploration of new territories are required.

AREAS COVERED

An overview of repurposed drugs and emerging treatments for schizophrenia is presented, focusing on randomized, controlled trials and meta-analyses.

EXPERT OPINION

Despite many years of drug research, several needs in the treatment of schizophrenia including the safety and tolerability, stage-dependent and personalized approaches, as well as drug delivery and sustainability have not been addressed sufficiently. Given the current failure of a number of mechanistically new drugs, repurposed compounds may serve as alternative and/or adjunctive agents for schizophrenic patients and for treatment refractory patients in particular. Anti-inflammatory drugs (e.g., acetylsalicylic acid, celecoxib and minocycline), as well as N-acetylcysteine, a precursor of the major antioxidant glutathione, hormones (e.g., estrogen, raloxifene and oxytocin), glutamatergic (e.g., glycine and d-serine) and nicotinergic compounds, 'nutraceuticals' (e.g., ω-3 fatty acids) and cannabidiol, an endocannabinoidmodulator, represent promising agents in this field.

Dementia praecox redux: a systematic review of the nicotinic receptor as a target for cognitive symptoms of schizophrenia

Most individuals with schizophrenia suffer some cognitive dysfunction: such deficits are predictive of longer-term functioning; and current dopamine-blocking antipsychotics have made little impact on this domain. There is a pressing need to develop novel pharmacological agents to tackle this insidious but most disabling of problems. The acetylcholinergic system is involved in cognitive and attentional processing, and its metabotropic and nicotinic receptors are widespread throughout the brain. Deficits in acetylcholinergic functioning occur in schizophrenia, and high rates of tobacco smoking have been posited to represent a form of self-medication. The nicotinic acetylcholine receptor (nAChR) has emerged as a putative target to improve cognitive deficits in schizophrenia, and this study systematically reviewed the emerging data. Nineteen studies were identified, covering three compound classes: agonists at the α7 and α 4β2 nAChRs, and positive allosteric modulators. Overall data are underwhelming: some studies showed significant improvements in cognition but as many studies had negative findings. It remains unclear if this represents drug limitations or nascent study methodology problems. The literature is particularly hindered by variability in inclusion of smokers, generally small sample sizes, and a lack of consensus on cognitive test batteries. Future work should evaluate longer-term outcomes, and, particularly, the effects of concomitant cognitive training.

Adjunctive pharmacotherapy for cognitive deficits in schizophrenia: meta-analytical investigation of efficacy

BACKGROUND

A growing number of studies have investigated the efficacy of novel, adjunctive pharmacotherapies for treatment of cognitive deficits in schizophrenia with conflicting results.

AIMS

To investigate the comparative efficacy of these agents on cognition and symptoms in schizophrenia, and to identify promising cognitive domains and candidate medications that can be incorporated in treatment trials combined with cognitive remediation to maximise treatment effects.

METHOD

A total of 26 double-blind, placebo-controlled studies investigating medications targeted at cholinergic, glutamatergic or serotonergic receptor classes and with participants with schizophrenia or schizoaffective disorder were identified.

RESULTS

Medications targeted at the cholinergic receptor class produced marginal improvements in verbal learning and memory (d = 0.23, P = 0.06), and donepezil, a specific type of cholinergic agonist, produced a moderate effect (d = 0.58) on spatial learning and memory. Cholinergic and glutamatergic agents produced moderate effect-size improvements on negative symptoms (d = 0.54 and d = 0.62 respectively), and small effect-size improvements on general symptoms (d = 0.46 and d = 0.41 respectively). Serotonergic agents produced small effect-size improvements in positive symptoms (d = 0.33).

CONCLUSIONS

Cholinergic medications produced marginal improvement in verbal learning and memory and moderate improvements on spatial learning and memory, although there was no evidence to support the use of glutamatergic or serotonergic medications as a stand-alone treatment for improving cognitive function. Cholinergic and glutamatergic agents improved negative and general symptoms, whereas serotenergic medications improved positive symptoms.

Comparison of the effectiveness of Conners' CPT and the CPT-identical pairs at distinguishing between smokers and nonsmokers with schizophrenia

Sustained attention deficits and high rates of smoking are often observed in patients with schizophrenia. This has led to the hypothesis that patients may smoke as an attempt to ameliorate cognitive deficits related to abnormal nicotinic structure and function. Continuous performance tasks (CPT) are often used to index sustained attention deficits in patients with schizophrenia, however, there are important differences between tasks that may impact performance in smokers and nonsmokers with schizophrenia differently. The Conners' CPT (C-CPT) has a high signal-to-noise ratio and is commonly used to assess impulsivity. The CPT-Identical Pairs (CPT-IP) has a low signal-to-noise ratio and is commonly used to assess negative symptoms in patients with schizophrenia. We sought to determine whether there were differences of sustained attention between patient smokers vs. nonsmokers, and if one CPT would provide a better separation of sustained attention between groups. Results revealed that both instruments detect more impaired sustained attention deficits in patient smokers compared to nonsmokers. Patient smokers performed significantly worse on the majority of the CPT-IP composite scores compared to the C-CPT composite scores. These results do not support the self-medication theory, as patient smokers performed worse than patient nonsmokers. Researchers studying sustained attention in schizophrenia may wish to consider the CPT-IP over the C-CPT, as well as control for smoking status.

Cholinergic connectivity: it's implications for psychiatric disorders

Acetylcholine has been implicated in both the pathophysiology and treatment of a number of psychiatric disorders, with most of the data related to its role and therapeutic potential focusing on schizophrenia. However, there is little thought given to the consequences of the documented changes in the cholinergic system and how they may affect the functioning of the brain. This review looks at the cholinergic system and its interactions with the intrinsic neurotransmitters glutamate and gamma-amino butyric acid as well as those with the projection neurotransmitters most implicated in the pathophysiologies of psychiatric disorders; dopamine and serotonin. In addition, with the recent focus on the role of factors normally associated with inflammation in the pathophysiologies of psychiatric disorders, links between the cholinergic system and these factors will also be examined. These interfaces are put into context, primarily for schizophrenia, by looking at the changes in each of these systems in the disorder and exploring, theoretically, whether the changes are interconnected with those seen in the cholinergic system. Thus, this review will provide a comprehensive overview of the connectivity between the cholinergic system and some of the major areas of research into the pathophysiologies of psychiatric disorders, resulting in a critical appraisal of the potential outcomes of a dysregulated central cholinergic system.

Cholinergic modulation of auditory processing, sensory gating and novelty detection in human participants

RATIONALE

Suppression of redundant auditory information and facilitation of deviant, novel, or salient sounds can be assessed with paired-click and oddball tasks, respectively. Electrophysiological correlates of perturbed auditory processing found in these paradigms are likely to be a trait marker or candidate endophenotype for schizophrenia.

OBJECTIVE

This is the first study to investigate the effects of the muscarinic M1 antagonist biperiden and the cholinesterase inhibitor rivastigmine on auditory-evoked potentials (AEPs), sensory gating, and mismatch negativity (MMN) in young, healthy volunteers.

RESULTS

Biperiden increased P50 amplitude and prolonged N100 and P200 latency in the paired-click task but did not affect sensory gating. Rivastigmine was able to reverse the effects of biperiden on N100 and P200 latency. Biperiden increased P50 latency in the novelty oddball task, which was reversed by concurrent administration of rivastigmine. Rivastigmine shortened N100 latency and enhanced P3a amplitude in the novelty oddball paradigm, both of which were reversed by biperiden.

CONCLUSION

The muscarinic M1 receptor appears to be involved in preattentive processing of auditory information in the paired-click task. Additional effects of biperiden versus rivastigmine were reversed by a combination treatment, which renders attribution of these findings to muscarinic M1 versus muscarinic M2-M5 or nicotinic receptors much more difficult. It remains to be seen whether the effects of cholinergic drugs on AEPs are specifically related to the abnormalities found in schizophrenia. Alternatively, aberrant auditory processing could also be indicative of a general disturbance in neural functioning shared by several neuropsychiatric disorders and/or neurodegenerative changes seen in aging.

Assessing the prospect of donepezil in improving cognitive impairment in patients with schizophrenia

INTRODUCTION

Even though cognitive impairment is manifested in almost all patients with schizophrenia, the Clinical Antipsychotic Trials for Intervention Effectiveness (CATIE) study showed no significant difference between first- and second-generation psychotropic drugs in improving cognitive abilities. Discovering new drugs that can improve impaired cognition, thus, is an attractive treatment target for patients with schizophrenia.

AREAS COVERED

This article briefly reviews about donepezil, a highly selective (IC(50) = 6.7 nM) centrally acting reversible acetylcholinesterase inhibitor that has been approved by FDA for treating cognitive deficit states such as in Alzheimer's disease and its uses in clinical trials for the treatment of schizophrenia. The literature search included PubMed and Cochrane library with the following words: donepezil, schizophrenia and cognitive impairments.

EXPERT OPINION

The results of several clinical trials utilizing donepezil as an adjunct to second-generation antipsychotic drugs targeting cognitive deficits in schizophrenia subjects have been disappointing and would not lead clinicians to consider this as a potential treatment option. While longer randomized controlled trials, increase dosage and selected groups of patients at different stage of cognitive impairment may provide a better understanding of the potential for this drug in addressing cognitive deficits, results to date have not been encouraging.

Pharmacological treatment of schizophrenia: a critical review of the pharmacology and clinical effects of current and future therapeutic agents

Since the introduction of chlorpromazine and throughout the development of the new-generation antipsychotic drugs (APDs) beginning with clozapine, the D(2) receptor has been the target for the development of APDs. Pharmacologic actions to reduce neurotransmission through the D(2) receptor have been the only proven therapeutic mechanism for psychoses. A number of novel non-D(2) mechanisms of action of APDs have been explored over the past 40 years but none has definitively been proven effective. At the same time, the effectiveness of treatments and range of outcomes for patients are far from satisfactory. The relative success of antipsychotics in treating positive symptoms is limited by the fact that a substantial number of patients are refractory to current medications and by their lack of efficacy for negative and cognitive symptoms, which often determine the level of functional impairment. In addition, while the newer antipsychotics produce fewer motor side effects, safety and tolerability concerns about weight gain and endocrinopathies have emerged. Consequently, there is an urgent need for more effective and better-tolerated antipsychotic agents, and to identify new molecular targets and develop mechanistically novel compounds that can address the various symptom dimensions of schizophrenia. In recent years, a variety of new experimental pharmacological approaches have emerged, including compounds acting on targets other than the dopamine D(2) receptor. However, there is still an ongoing debate as to whether drugs selective for singe molecular targets (that is, 'magic bullets') or drugs selectively non-selective for several molecular targets (that is, 'magic shotguns', 'multifunctional drugs' or 'intramolecular polypharmacy') will lead to more effective new medications for schizophrenia. In this context, current and future drug development strategies can be seen to fall into three categories: (1) refinement of precedented mechanisms of action to provide drugs of comparable or superior efficacy and side-effect profiles to existing APDs; (2) development of novel (and presumably non-D(2)) mechanism APDs; (3) development of compounds to be used as adjuncts to APDs to augment efficacy by targeting specific symptom dimensions of schizophrenia and particularly those not responsive to traditional APD treatment. In addition, efforts are being made to determine if the products of susceptibility genes in schizophrenia, identified by genetic linkage and association studies, may be viable targets for drug development. Finally, a focus on early detection and early intervention aimed at halting or reversing progressive pathophysiological processes in schizophrenia has gained great influence. This has encouraged future drug development and therapeutic strategies that are neuroprotective. This article provides an update and critical review of the pharmacology and clinical profiles of current APDs and drugs acting on novel targets with potential to be therapeutic agents in the future.

Nicotine fails to attenuate ketamine-induced cognitive deficits and negative and positive symptoms in humans: implications for schizophrenia

BACKGROUND

The uncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, ketamine, induces a range of symptoms resembling those seen in schizophrenia. Enhancement of nicotinic acetylcholine receptor (nAChR) function may have potential as a treatment for the cognitive deficits and negative symptoms of schizophrenia. Accordingly, we examined the modulatory effects of brain nAChR systems on NMDAR antagonist-induced effects.

METHODS

The interactive effects of ketamine and nicotine were evaluated in 37 healthy subjects in a randomized, placebo-controlled, double-blind, crossover counterbalanced, 2 (intravenous ketamine or placebo) × 2 (intravenous nicotine or placebo) design. Verbal and visual memory, sustained attention, working memory, response inhibition, emotion recognition, executive function, reaction time, motor function, and speed of processing were assessed once per test day, while negative and positive symptoms, perceptual alterations, and a number of feeling states were measured several times before and after administration of drugs.

RESULTS

Ketamine induced cognitive deficits and negative and positive symptoms. Nicotine worsened immediate recall, auditory working memory, response inhibition, and executive function and serial processing. Nicotine decreased (improved) reaction time on the sustained attention and choice reaction time tasks. Nicotine did not reduce ketamine-induced cognitive deficits or negative and positive symptoms.

CONCLUSIONS

At blood levels comparable with tobacco smoking, nicotine infusion does not appear to alleviate the ketamine-induced transient cognitive and behavioral effects in healthy subjects that resemble those seen in schizophrenia. The lack of an effect of nicotine on a spectrum of ketamine effects suggests that the consequences of NMDAR antagonism are not likely under the direct influence of nAChR.

The nicotinic α7 receptor agonist GTS-21 improves cognitive performance in ketamine impaired rhesus monkeys

The cognitive deficits associated with schizophrenia are recognized as a core component of the disorder, yet there remain no available therapeutics to treat these symptoms of the disease. As a result, there is a need for establishing predictive preclinical models to identify the therapeutic potential of novel compounds. In the present study, rhesus monkeys were trained in the object retrieval-detour task, which is dependent on the prefrontal cortex, a brain region implicated in the cognitive deficits associated with schizophrenia. The NMDA receptor antagonist ketamine significantly impaired performance without affecting measures of motor or visuospatial abilities. Pre-treatment with the nicotinic α7 agonist GTS-21 (0.03 mg/kg) significantly attenuated the ketamine-induced impairment, consistent with reports from clinical trials suggesting that nicotinic α7 receptor agonism has pro-cognitive potential in clinical populations. In contrast, pretreatment with the acetylcholinesterase inhibitor donepezil failed to reverse the ketamine-induced impairment, consistent with studies showing a lack of pro-cognitive effects in patients with schizophrenia. These data suggest that the ketamine-impaired object retrieval-detour task could provide a model with improved predictive validity for drug development, and confirm the need for additional efforts in back-translation. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Spontaneous object recognition and its relevance to schizophrenia: a review of findings from pharmacological, genetic, lesion and developmental rodent models

RATIONALE

Spontaneous (novel) object recognition (SOR) is one of the most widely used rodent behavioural tests. The opportunity for rapid data collection has made SOR a popular choice in studies that explore cognitive impairment in rodent models of schizophrenia, and that test the efficacy of drugs intended to reverse these deficits.

OBJECTIVES

We provide an overview of the many recent studies that have used SOR to explore the mnemonic effects of manipulation of the key transmitter systems relevant to schizophrenia-the dopamine, glutamate, GABA, acetylcholine, serotonin and cannabinoid systems-alone or in combination. We also review the use of SOR in studying memory in genetically modified mouse models of schizophrenia, as well as in neurodevelopmental and lesion models. We end by discussing the construct and predictive validity, and translational relevance, of SOR with respect to cognitive impairment in schizophrenia.

RESULTS

Perturbation of the dopamine or glutamate systems can generate robust and reliable impairment in SOR. Impaired performance is also seen following antagonism of the muscarinic acetylcholine system, or exposure to cannabinoid agonists. Cognitive enhancement has been reported using alpha7-nicotinic acetylcholine receptor agonists and 5-HT(6) antagonists. Among non-pharmacological models, neonatal ventral hippocampal lesions and maternal immune activation can impair SOR, while mixed results have been obtained with mice carrying mutations in schizophrenia risk-associated genes, including neuregulin and COMT.

CONCLUSIONS

While SOR is not without its limitations, the task represents a useful method for studying manipulations with relevance to cognitive impairment in schizophrenia, as well as the interactions between them.

Can genetics inform the management of cognitive deficits in schizophrenia?

There is no doubt that schizophrenia has a significant genetic component and a number of candidate genes have been identified for this debilitating disorder. Of note, several of these are implicated in cognition. Cognitive deficits constitute core symptoms of schizophrenia, and while current antipsychotic treatment strategies aim to help psychosis-related symptomatology, the cognitive symptom domain is largely inadequately treated. A number of other pharmacological approaches (e.g. using drugs that target specific neurotransmitter systems) have also been attempted for the amelioration of cognitive deficits in this population; however, these too have had limited success so far. Psychological interventions appear promising, though there has been speculation regarding whether or not these produce long-term functional improvements. Pharmacogenetic studies of the cognitive effects of currently available antipsychotics, although in relatively early stages, suggest that the treatment of cognitive deficits in schizophrenia may be advanced by focusing on genetic variants associated with specific cognitive dysfunctions in the general population and using this to match the most relevant pharmacological and/or psychological interventions with the genetic and cognitive profiles of the target population. Such a strategy would encourage bottom-up advances in drug development and provide a platform for individualised treatment of cognitive deficits in schizophrenia.

Acetylcholinesterase inhibitors for schizophrenia

BACKGROUND

Antipsychotic medication remains the mainstay of treatment for schizophrenia and has been in use for a long time. As evidenced by ongoing research and partial effectiveness of the antipsychotics on cognitive and negative symptoms, the search is on for drugs that may improve these domains of functioning for someone suffering from schizophrenia. Acetylcholinesterase inhibitors have long been in use for treating cognitive symptoms of dementia.

OBJECTIVES

The aim of the review was to evaluate the clinical effects, safety and cost effectiveness of acetylcholinesterase inhibitors for treating people with schizophrenia

SEARCH METHODS

We searched the Cochrane Schizophrenia Group's Register (February 2009), and inspected the references of all identified studies for further trials.

SELECTION CRITERIA

We included all clinical randomised trials comparing acetylcholinesterase inhibitors with antipsychotics or placebo either alone, or in combination, for schizophrenia and schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

We extracted data independently. For dichotomous data, we calculated risk ratios (RR) and their 95% confidence intervals (CI) on an intention-to-treat (ITT) basis based on a random-effects model. For continuous data, we calculated mean differences (MD), again based on a random-effects model.

MAIN RESULTS

The acetylcholinesterase inhibitor plus antipsychotic showed benefit over antipsychotic and placebo in the following outcomes.1. Mental state - PANSS negative symptoms average end point score (2 RCTs, n = 31, MD -1.69 95% CI -2.80 to -0.57), PANSS General Psychopathology average end point score (2 RCTs, n = 31, MD -3.86 95% CI -5.40 to -2.32), and improvement in depressive symptoms showed at least by one short-term study as measured by CDSS scale (data skewed).2. Cognitive domains - attention, (1 RCT, n = 73, MD 1.20 95% CI 0.14 to 2.26), visual memory (2 RCTs, n = 48 , MD 1.90 95% CI 0.52 to 3.28), verbal memory and language (3 RCTs, n = 42, MD 3.46 95% CI 0.67 to 6.26) and executive functioning (1 RCT, n = 24, MD 17.10 95% CI 0.70 to 33.50).3. Tolerability - EPSE: AIMS, (1 RCT, n = 35, MD 1.50 95% CI 1.04 to 1.96).No difference was noted between the two arms in other outcomes. The overall rate of participants leaving studies early was low (13.6 %) and showed no clear difference between the two groups.

AUTHORS' CONCLUSIONS

The results seem to favour the use of acetylcholinesterase inhibitors in combination with antipsychotics on a few domains of mental state and cognition, but because of the various limitations in the studies as mentioned in the main text, the evidence is weak. This review highlights the need for large, independent, well designed, conducted and reported pragmatic randomised studies.

The effects of donepezil on computer-simulated driving ability among healthy older adults: a pilot study

The purpose of the present pilot study was to examine the effect of donepezil on simulated driving among healthy older adults. Twenty participants with a mean age of 72 years were randomized to take 5 mg of donepezil or placebo for 2 weeks. All participants were assessed at baseline and 2 weeks later on measures of attention, global cognition, and simulated driving on the York driving simulator. Driving measures included speed deviation, deviation of road position, reaction time to wind gusts, and collisions. Groups were compared using analysis of covariance, controlling for baseline values. There were no differences between the groups on attentional measures, number of collisions, or composite simulator measures. The placebo group fared approximately 0.5 second better in reaction time to wind gusts and showed a nonsignificant tendency toward less deviation of road position, compared with the donepezil group. This analysis does not support the use of donepezil to extend the period of safe driving among older adults, but further study is needed regarding its role among patients with cognitive disorders.

Neuropsychological performance in patients with schizophrenia and controls as a function of cigarette smoking status

Schizophrenia is associated with many neurocognitive deficits, some of which are improved by nicotine and cigarette smoking. To better understand the relationship between smoking and cognitive function in schizophrenia, cross-sectional assessment of neuropsychological performance as a function of smoking status (smoker or non-smoker) and smoking history (current, former or never-smoker) in clinically stable outpatients with schizophrenia and controls was evaluated. Subjects (n=140) were divided into subgroups on the basis of self-report and biochemical verification of smoking history. Current smokers with schizophrenia (n=38), former smokers with schizophrenia (n=17), never-smokers with schizophrenia (n=12), control smokers (n=31), control former smokers (n=16), and control never-smokers (n=26) were administered a comprehensive neuropsychological battery. Smokers were studied under non-deprivation conditions. Comparison of neuropsychological performance in schizophrenia and control subjects revealed significant main effects of diagnosis. Analysis of the data as a function of smoking history demonstrated that never-smokers with schizophrenia performed the poorest on measures of sustained attention, processing speed and response inhibition, when compared to the other schizophrenia subgroups. Cigarette smoking did not alter neuropsychological performance in controls. Our findings suggest that smoking status and history differentially alters neuropsychological outcomes in schizophrenia compared to non-psychiatric controls, and that never-smokers may present with more severe neurocognitive impairments.

Effects of moderate-dose treatment with varenicline on neurobiological and cognitive biomarkers in smokers and nonsmokers with schizophrenia or schizoaffective disorder

CONTEXT

The administration of nicotine transiently improves many neurobiological and cognitive functions in schizophrenia and schizoaffective disorder. It is not yet clear which nicotinic acetylcholine receptor (nAChR) subtype or subtypes are responsible for these seemingly pervasive nicotinic effects in schizophrenia and schizoaffective disorder.

OBJECTIVE

Because α4β2 is a key nAChR subtype for nicotinic actions, we investigated the effect of varenicline tartrate, a relatively specific α4β2 partial agonist and antagonist, on key biomarkers that are associated with schizophrenia and are previously shown to be responsive to nicotinic challenge in humans.

DESIGN

A double-blind, parallel, randomized, placebo-controlled trial of patients with schizophrenia or schizoaffective disorder to examine the effects of varenicline on biomarkers at 2 weeks (short-term treatment) and 8 weeks (long-term treatment), using a slow titration and moderate dosing strategy for retaining α4β2-specific effects while minimizing adverse effects.

SETTING

Outpatient clinics.

PARTICIPANTS

A total of 69 smoking and nonsmoking patients; 64 patients completed week 2, and 59 patients completed week 8. Intervention Varenicline.

MAIN OUTCOME MEASURES

Prepulse inhibition, sensory gating, antisaccade, spatial working memory, eye tracking, processing speed, and sustained attention.

RESULTS

A moderate dose of varenicline (1) significantly reduced the P50 sensory gating deficit in nonsmokers after long-term treatment (P = .006), (2) reduced startle reactivity (P = .02) regardless of baseline smoking status, and (3) improved executive function by reducing the antisaccadic error rate (P = .03) regardless of smoking status. A moderate dose of varenicline had no significant effect on spatial working memory, predictive and maintenance pursuit measures, processing speed, or sustained attention by Conners' Continuous Performance Test. Clinically, there was no evidence of exacerbation of psychiatric symptoms, psychosis, depression, or suicidality using a gradual titration (1-mg daily dose).

CONCLUSIONS

Moderate-dose treatment with varenicline has a unique treatment profile on core schizophrenia-related biomarkers. Further development is warranted for specific nAChR compounds and dosing and duration strategies to target subgroups of schizophrenic patients with specific biological deficits.

Effects of adjunct galantamine to risperidone, or haloperidol, in animal models of antipsychotic activity and extrapyramidal side-effect liability: involvement of the cholinergic muscarinic receptor

The acetylcholine esterase inhibitor/cholinergic nicotinic receptor (nAChR) allosteric modulator galantamine (Gal) is used against cognitive impairment in Alzheimer's disease. Negative/cognitive and psychotic symptom improvement in schizophrenia by adjunct Gal to antipsychotic drugs (APDs) has been reported. Cognitive symptoms in schizophrenia may involve brain prefrontal hypo-dopaminergia. Experimental data by others indicate nAChR involvement in animal pro-cognitive effects of Gal. The role of nAChRs in antipsychotic effects by Gal has, however, not been elucidated. Using the conditioned avoidance response (CAR) and the catalepsy tests for antipsychotic activity and extrapyramidal side-effect (EPS) liability, respectively, we here investigated the effects of adjunct Gal (1.25 mg/kg) to the typical APD haloperidol (Hal) (0.05 mg/kg), or the atypical APD risperidone (Ris) (0.2 mg/kg), in rats. Adjunct Gal significantly enhanced APD-like effects by low doses of Hal or Ris, but showed a safe EPS liability profile only in combination with Ris. Pretreatment with the muscarinic receptor (mAChR) antagonist scopolamine, but not the nAChR antagonist mecamylamine, completely reversed the enhancing effects of adjunct Gal to Hal treatment, in the CAR test. While the nAChR-modulating properties of Gal probably contribute to pro-cognitive activity, as shown by others, the present data suggest that any contribution to antipsychotic activity by Gal is mediated primarily via mAChRs. This property combination of Gal may offer a unique, favourable therapeutic profile for schizophrenia treatment.

Emerging drugs for schizophrenia

INTRODUCTION

Since the development of clozapine, scores of antipsychotics have been introduced. These are, with one exception (aripiprazole), based on the pharmacological principle of 5-HT(2)/dopamine antagonism. Research on other treatment targets, which, in part, influence dopaminergic pathways directly or indirectly, is mounting. Managing psychotic symptoms is only one facet of successful treatment of schizophrenia. Effective remedies against negative symptoms and cognitive deficits are still an unmet clinical need.

AREAS COVERED

With the focus on the topics mentioned above, the authors briefly review the latest clinical research organized on the basis of receptor systems and other drug targets, which are discussed to be involved in the pathophysiology of schizophrenia.

EXPERT OPINION

In conclusion, although clinicians will have to have considerable patience before truly novel anti-schizophrenia treatments become obtainable, a number of interesting leads with considerable theoretical potential are being explored. As yet, it is difficult to predict which of these mechanisms will effectively augment the currently available treatments.

Pharmacological aspects of the acetylcholinesterase inhibitor galantamine

Several lines of evidence suggest that cholinergic deficits may contribute to the pathophysiology of psychiatric disorders as well as Alzheimer's disease. There is growing clinical evidence that galantamine, currently used for the treatment of Alzheimer's disease, may improve cognitive dysfunction and psychiatric illness in schizophrenia, major depression, bipolar disorder, and alcohol abuse. Since galantamine is a rather weak acetylcholinesterase inhibitor, but has additional allosteric potentiating effects at nicotinic receptors, it affects not only cholinergic transmission but also other neurotransmitter systems such as monoamines, glutamate, and γ-aminobutyric acid (GABA) through its allosteric mechanism. It is likely that these effects may result in more beneficial effects. To understand the underlying mechanism for the clinical effectiveness of galantamine, neuropharmacological studies have been performed in animal models of several psychiatric disorders. These studies suggest that not only the nicotinic receptor-modulating properties but also the muscarinic receptor activation contribute to the antipsychotic effect and improvement of cognitive dysfunction by galantamine. This review summaries the current status on the pharmacology of galantamine, focusing on its effect on neurotransmitter release and pharmacological studies in animal models of psychiatric disorders.

Galantamine augmentation of long-acting injectable risperidone for cognitive impairments in chronic schizophrenia

BACKGROUND

Galantamine, a reversible cholinesterase inhibitor with effects on nicotinic receptors, has shown mixed effects on cognitive impairments in patients with schizophrenia. Given these mixed results we examined whether galantamine compared to adjunctive placebo may improve cognitive functions in patients treated concomitantly with a long acting atypical antipsychotic.

METHOD

The parent study was a 52-week double-blind, randomized study of treatment with long-acting injectable risperidone 25mg or 50mg every two weeks. Adjunctive galantamine or placebo treatment was administered from Month 6 to 12. Outcome measures were neurocognitive, psychopathology, social and quality of life functions. Patients were randomized to blinded galantamine up to 24mg/day or matching placebo tablets. All patients were maintained on their randomized long-acting injectable risperidone regimen for the duration of the trial.

RESULTS

32 patients were included in the intent-to-treat analysis. No statistically significant differences were found for Attention Vigilance, Declarative Memory, Processing Speed, Reasoning/Problem Solving, Working Memory domains and the Neurocognitive Composite Score. Group specific analysis showed a statistically significant group interaction (p=0.043) with the Social Cognition domain showing in the galantamine group significantly lower scores at endpoint than placebo patients. The PANSS general psychopathology subscale showed significantly higher scores in the galantamine group at endpoint (p=0.05). ANCOVA model for within treatment group comparisons showed a significant increase of 7.3 points for the total PANSS score for the galantamine group.

CONCLUSION

Galantamine showed no ameliorative effects on cognitive measures in this 6month, double-blind study of patients with schizophrenia treated with an assured and stable antipsychotic medication delivery system. Galantamine may not be an appropriate augmentation agent for cognitive impairments in patients with schizophrenia at the dose used.

Cholinergic contributions to the cognitive symptoms of schizophrenia and the viability of cholinergic treatments

Effective treatment of the cognitive symptoms of schizophrenia has remained an elusive goal. Despite the intense focus on treatments acting at or via cholinergic mechanisms, little remains known about the dynamic cholinergic abnormalities that contribute to the manifestation of the cognitive symptoms in patients. Evidence from basic neuroscientific and psychopharmacological investigations assists in proposing detailed cholinergic mechanisms and treatment targets for enhancement of attentional performance. Dynamic, cognitive performance-dependent abnormalities in cholinergic activity have been observed in animal models of the disorder and serve to further refine such proposals. Finally, the potential usefulness of individual groups of cholinergic drugs and important issues concerning the interactions between pro-cholinergic and antipsychotic treatments are addressed. The limited evidence available from patient studies and animal models indicates pressing research needs in order to guide the development of cholinergic treatments of the cognitive symptoms of schizophrenia.

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.

Genetics and intermediate phenotypes of the schizophrenia--bipolar disorder boundary

Categorization of psychotic illnesses into schizophrenic and affective psychoses remains an ongoing controversy. Although Kraepelinian subtyping of psychosis was historically beneficial, modern genetic and neurophysiological studies do not support dichotomous conceptualization of psychosis. Evidence suggests that schizophrenia and bipolar disorder rather present a clinical continuum with partially overlapping symptom dimensions, neurophysiology, genetics and treatment responses. Recent large scale genetic studies have produced inconsistent findings and exposed an urgent need for re-thinking phenomenology-based approach in psychiatric research. Epidemiological, linkage and molecular genetic studies, as well as studies in intermediate phenotypes (neurocognitive, neurophysiological and anatomical imaging) in schizophrenia and bipolar disorders are reviewed in order to support a dimensional conceptualization of psychosis. Overlapping and unique genetic and intermediate phenotypic signatures of the two psychoses are comprehensively recapitulated. Alternative strategies which may be implicated into genetic research are discussed.

Cholinesterase inhibitors as adjunctive therapy in patients with schizophrenia and schizoaffective disorder: a review and meta-analysis of the literature

BACKGROUND

Cognitive deficits have been described in patients with schizophrenia from the first descriptions of dementia praecox to current concepts of cognitive dysmetria. Nevertheless, little is known about how to deal with them. In Alzheimer disease, cholinergic deficit is found and cholinesterase inhibitors have been used to delay the progression of memory and cognitive dysfunction. Several lines of evidence suggest that the cholinergic system may be disrupted in schizophrenia.

OBJECTIVE

To evaluate cognitive and clinical effects of adjunctive cholinesterase inhibitors in patients with schizophrenia and schizoaffective disorder.

METHOD

We conducted a literature search on PubMed and EMBASE (up to December 2008) for articles that investigated adjunctive cholinesterase inhibitors in patients with schizophrenia. The terms 'schizophrenia', 'acetylcholinesterase inhibitors', 'rivastigmine', 'donepezil', 'galantamine' and 'cognitive deficit' were searched with restriction for English language and without a year limit. All articles that presented original data from randomized, double-blind, placebo-controlled trials with donepezil, rivastigmine or galantamine in patients with schizophrenia or schizoaffective disorder were included in the meta-analysis. Studies were excluded for the following reasons: (i) case study/letter/correspondence/review; (ii) animal study; (iii) molecular/genetic investigation; and (iv) inclusion of patients with schizophrenia and co-morbid dementia. Few appropriate data for meta-analysis were found because of the large heterogeneity of the assessment instruments used. Nevertheless, effects of cholinesterase inhibitors in some cognitive domains (executive function, memory and language), psychopathology (using the Positive and Negative Syndrome Scale) and extrapyramidal symptoms could be analysed.

RESULTS

Six open-label and 24 double-blind studies were found. In five open-label studies there was an improvement in memory, attention and executive functions. Thirteen double-blind studies (four with rivastigmine, six with donepezil and three with galantamine) contributed to the meta-analysis. Significant improvement was found in this analysis for memory and the Trail Making test part A.

CONCLUSIONS

The reviewed studies suggest that specific cognitive deficits (memory, and the motor speed and attention part of executive function) of patients with schizophrenia and schizoaffective disorder are responsive to rivastigmine, donepezil and galantamine as adjunctive therapy. Confirmatory studies are needed to determine the clinical utility of this treatment strategy.

Polypharmacy in schizophrenia

PURPOSE OF REVIEW

Although most guidelines recommend monotherapy in schizophrenia, the combined application of multiple psychotropic agents is very common, especially in treatment-refractory cases. We review the empirical basis supporting these attempts and their relevance for clinical practice.

RECENT FINDINGS

Polypharmacy intends to address different aspects of treatment resistance, most importantly insufficient response of psychotic positive and negative symptoms, but also cognitive disturbances, affective comorbidity, obsessive-compulsive syndromes and side-effects of antipsychotic drugs. This review summarizes the current state of evidence of combined antipsychotic treatment strategies and the augmentation of antipsychotics with mood stabilizers, antidepressants and experimental substances.

SUMMARY

In general, rigorous data on combination therapy in schizophrenia are rare and further randomized controlled trials, naturalistic trials and head-to-head-trials are necessary. Some evidence supports a combination of antipsychotics and antidepressants for negative symptoms and comorbid major depressive episodes. The add-on of lithium and mood stabilizers lacks compelling evidence, but might be beneficial for specific subgroups. For treatment-resistant cognitive symptoms, antipsychotic medication should be combined with cognitive remediation, as no pharmacological add-on strategy has gained convincing evidence so far. Treatment-emergent positive and/or negative symptoms under clozapine monotherapy might benefit from adding a second atypical substance.

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.

Alterações cognitivas na esquizofrenia: atualização

As alterações cognitivas são características centrais na esquizofrenia. Elas permanecem relativamente estáveis durante todo o curso da doença, não sendo secundárias a outros sintomas ou a efeitos colaterais de psicofármacos. Estão diretamente ligadas a prejuízo funcional e a pior qualidade de vida dos pacientes. Diversos estudos vêm sendo realizados no sentido de caracterizar as principais alterações cognitivas na esquizofrenia, identificar suas bases neurobiológicas e padronizar instrumentos de pesquisa, fundamentais para o advento de novos alvos para intervenções farmacológicas na esquizofrenia. O objetivo deste trabalho foi fazer uma atualização sobre o assunto.

Animal models of schizophrenia

Schizophrenia may well represent one of the most heterogenous mental disorders in human history. This heterogeneity encompasses (1) etiology; where numerous putative genetic and environmental factors may contribute to disease manifestation, (2) symptomatology; with symptoms characterized by group; positive--behaviors not normally present in healthy subjects (e.g. hallucinations), negative--reduced expression of normal behaviors (e.g. reduced joy), and cognitive--reduced cognitive capabilities separable from negative symptoms (e.g. impaired attention), and (3) individual response variation to treatment. The complexity of this uniquely human disorder has complicated the development of suitable animal models with which to assay putative therapeutics. Moreover, the development of animal models is further limited by a lack of positive controls because currently approved therapeutics only addresses psychotic symptoms, with minor negative symptom treatment. Despite these complexities however, many animal models of schizophrenia have been developed mainly focusing on modeling individual symptoms. Validation criteria have been established to assay the utility of these models, determining the (1) face, (2) predictive, (3) construct, and (4) etiological validities, as well as (5) reproducibility of each model. Many of these models have been created following the development of major hypotheses of schizophrenia, including the dopaminergic, glutamatergic, and neurodevelopmental hypotheses. The former two models have largely consisted of manipulating these neurotransmitter systems to produce behavioral abnormalities with some relevance to symptoms or putative etiology of schizophrenia. Given the serotonergic link to hallucinations and cholinergic link to attention, other models have manipulated these systems also. Finally, there has also been a drive toward creating mouse models of schizophrenia utilizing transgenic technology. Thus, there are opportunities to combine both environmental and genetic factors to create more suitable models of schizophrenia. More sophisticated animal tasks are also being created with which to ascertain whether these models produce behavioral abnormalities consistent with patients with schizophrenia. While animal models of schizophrenia continue to be developed, we must be cognizant that (1) validating these models are limited to the degree by which Clinicians can provide relevant information on the behavior of these patients, and (2) any putative treatments that are developed are also likely to be given with concurrent antipsychotic treatment. While our knowledge of this devastating disorder increases and our animal models and tasks with which to measure their behaviors become more sophisticated, caution must still be taken when validating these models to limit complications when introducing putative therapeutics to human trials.

Smoking, nicotine and neuropsychiatric disorders

Tobacco smoking is an extremely addictive and harmful form of nicotine (NIC) consumption, but unfortunately also the most prevalent. Although disproportionately high frequencies of smoking and its health consequences among psychiatric patients are widely known, the neurobiological background of this epidemiological association is still obscure. The diverse neuroactive effects of NIC and some other major tobacco smoke constituents in the central nervous system may underlie this association. This present paper summarizes the pharmacology of NIC and its receptors (nAChR) based on a systematic review of the literature. The role of the brain's reward system(s) in NIC addiction and the results of functional and structural neuroimaging studies on smoking-related states and behaviors (i.e. dependence, craving, withdrawal) are also discussed. In addition, the epidemiological, neurobiological, and genetic aspects of smoking in several specific neuropsychiatric disorders are reviewed and the clinical relevance of smoking in these disease states addressed.

Identifying and treating cognitive impairment in bipolar disorder

OBJECTIVES

The presence of cognitive deficits has become increasingly appreciated across all phases of bipolar disorder. The present review sought to identify domains of cognitive dysfunction, methods of assessment, discrimination of iatrogenic from illness-specific etiologies, and pharmacologic strategies to manage cognitive problems in patients with bipolar disorder.

METHODS

A selective literature review was performed focusing on studies of descriptive phenomenology and pharmacologic intervention (favoring randomized comparisons when existent but open trials or case reports when not) involving cognition in bipolar disorder populations, healthy volunteers, or other clinical populations. Identification was made of (i) practical strategies for clinical assessment and management of cognitive complaints, (ii) limitations of existing intervention studies, and (iii) recommendations for the design and direction of future research.

RESULTS

Cognitive deficits involving attention, executive function, and verbal memory are evident across all phases of bipolar disorder. Most existing treatment studies involve nonbipolar populations, prompting caution when extrapolating outcomes to individuals with bipolar disorder. Differentiating medication- from illness-induced cognitive dysfunction requires comprehensive assessment with an appreciation for the cognitive domains most affected by specific medications. No current pharmacotherapies substantially improve cognition in bipolar disorder, although preliminary findings suggest some potential value for adjunctive stimulants such as modafinil and novel experimental agents.

CONCLUSIONS

Circumscribed cognitive deficits may be both iatrogenic and intrinsic to bipolar disorder. Optimal management hinges on a knowledge of illness-specific cognitive domains as well as of the beneficial or adverse cognitive profiles of common psychotropic medications.

Antipsychotics in the early stage of development

PURPOSE OF REVIEW

In this article, we will summarize some of the most recent pharmacological approaches by briefly reviewing the latest research results related to different neurotransmitter receptor systems but also alternative approaches that do not affect central nervous system receptors directly.

RECENT FINDINGS

Although the field still struggles with the lack of major breakthroughs, some novel pharmacological leads have provided encouraging findings in proof of concept or early phase II clinical trials. Although some of these approaches are based on the modified dopamine/glutamate hypothesis of schizophrenia, others appear to have been driven by more serendipitous observations. Apart from this, more traditional routes such as compounds targeting D2/HT2 receptors are also still being pursued. Attempts to advance treatment response of negative symptoms and cognitive impairment, two areas of considerable unmet need have been an overriding theme in many studies.

SUMMARY

Clinical psychopharmacologists increasingly realize that it is highly unlikely that we have a magic bullet to treat adequately all aspects of this complex disorder in the foreseeable future. Rational polypharmacy may be the trend for the next decade.

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.

Predictors of early abstinence in smokers with schizophrenia

BACKGROUND

In patients with schizophrenia, the smoking cessation rate is low and the burden of smoking-related morbidity and mortality is high. Identification of factors associated with abstinence may allow clinicians to optimize treatment prior to a smoking cessation attempt.

METHOD

To identify factors associated with successful smoking cessation in patients with a DSM-IV diagnosis of schizophrenia, we analyzed baseline data from 114 stable outpatient smokers with schizophrenia who participated in 1 of 2 smoking cessation trials. The outcome of interest was 4 weeks' continuous abstinence at the end of a 12-week nicotine dependence treatment intervention. Baseline factors associated with abstinence were identified with univariate methods and entered into a manual, forward-selection multivariable regression model to identify independent predictors of abstinence. The study was conducted from March 1999 to February 2004.

RESULTS

Fourteen of 114 participants (12%) had biochemically verified 4 weeks' continuous abstinence at week 12. We included 10 noncorrelated variables with a univariate association with abstinence in a multivariable model, controlling for pharmacotherapy, age, and gender. Age at initiation of smoking and baseline variability in attentiveness, as measured by Continuous Performance Test-AX (CPT-AX) hit reaction time standard error, were independently associated with abstinence. For every year increase in age at initiation of smoking, the OR for abstinence was 1.36 (95% CI = 1.01 to 1.83), p = .048. For every millisecond decrease in the variability of the reaction time of CPT-AX, the OR for achieving abstinence was 1.55 (95% CI = 1.07 to 2.24), p = .021.

CONCLUSION

Later initiation of smoking was associated with increased and baseline attentional impairment with reduced odds of abstinence. Additional research to further our understanding of the relationship between attentional impairment and cigarette smoking in schizophrenia may lead to improved nicotine dependence treatments for this group.