Effects of antipsychotics on cognitive performance in drug-naive schizophrenic patients

The effect of antipsychotics on the cognitive performance of individuals with psychotic disorders: Network meta-analyses of randomized controlled trials

Cognitive deficits are a core aspect of psychotic disorders; however, it is not clear to which extent different pharmacological treatments could distinctly impact these outcomes. Hence, we conducted a systematic review and ten network meta-analyses of randomized controlled trials to compare the effect of antipsychotics on cognitive performance of individuals with psychotic disorders. Fifty-four trials were included in the analyses, enrolling 5866 patients. Compared to other antipsychotics, amisulpride performed better on verbal learning; quetiapine on composite score, attention and verbal learning; lurasidone on composite score; olanzapine on composite score and most cognitive domains; perphenazine on composite score, executive function, working memory, and verbal learning; risperidone on executive function and verbal learning; sertindole on processing speed; and ziprasidone on composite score, working memory, and verbal learning. Oppositely, haloperidol performed poorer on all cognitive domains, occupying the last positions in all rankings; and clozapine performed poorer on composite score, executive function, verbal learning, and visuoconstruction. We hope that these results should be taken into account when assessing and treating individuals with psychosis.

Psychopathological Symptom Load and Distinguishable Cerebral Blood Flow Velocity Patterns in Patients With Schizophrenia and Healthy Controls: A Functional Transcranial Doppler Study

Introduction: Schizophrenia is a severe psychiatric disorder, with executive dysfunction and impaired processing speed playing a pivotal role in the course of the disease. In patients with schizophrenia, neurocognitive deficits appear to be related to alterations in cerebral hemodynamics. It is not fully understood if psychopathological symptom load (i.e., presence and severity of symptoms) is also related to alterations in cerebral hemodynamics. We aim to study the relationship between psychopathological symptom load and cerebral hemodynamics in the Middle Cerebral Artery (MCA) during a cognitive task in patients with schizophrenia and healthy controls. Methodology: Cerebral hemodynamics in the MCA were examined in 30 patients with schizophrenia and 15 healthy controls using functional Transcranial Doppler (fTCD) during the Trail Making Test (TMT). Psychopathological symptoms were measured using the Brief Psychiatric Rating Scale (BPRS). Patients were dichotomized according to BPRS scores: mild-moderate (BPRS < 41, n = 15) or marked-severe (BPRS ≧ 41, n = 15). Mean blood flow velocity (MFV) in the MCA and processing speed of the TMT were analyzed. Cerebral hemodynamics were analyzed using the general additional model (GAM) with a covariate analysis of variance (ANCOVA) for group comparisons. Results: Patients and healthy controls were comparable regarding demographics. Patients had a slower processing speed for the TMT-A (patients-severe: 52s, patients-moderate: 40s, healthy-controls: 32s, p = 0.019) and TMT-B [patients-severe: 111s, patients-moderate: 76s, healthy-controls: 66s, p < 0.001)]. Patients demonstrated differing hemodynamic profiles in both TMTs: TMT- A [F _{(6, 1,792)} = 17, p < 0.000); TMT-B [F _{(6, 2,692)} = 61.93, p < 0.000], with a delay in increase in MFV and a failure to return to baseline values. Conclusions: Patients with schizophrenia demonstrated slower speeds of processing during both the TMT-A and TMT-B. The speed of processing deteriorated with increasing psychopathological symptom load, additionally a distinct cerebral hemodynamic pattern in the MCA was observed. Our results further support the view that severity of schizophrenia, particularly psychopathological symptom load, influences performance in neurocognitive tasks and is related to distinct patterns of brain hemodynamics.

The Association Between Cognitive Deficits and Clinical Characteristic in First-Episode Drug Naïve Patients With Schizophrenia

Background: Schizophrenia is a severe mental disease which characterized by positive symptom, negative symptom, general pathology syndrome and cognitive deficits. In recent years, many studies have investigated the relationship between cognitive deficits and clinical characteristics in schizophrenia, but relatively few studies have been performed on first-episode drug-naïve patients. Methods: Eighty seven first-episode drug-naïve schizophrenia patients were assessed for positive symptom, negative symptom, general pathology symptom and cognitive deficits from the Positive and Negative Symptom Scale and MATRICS Consensus Cognitive Battery. Psychotics depression were assessed using the Calgary depressing scale for schizophrenia. The relationship between clinical characteristics and cognitive deficits were assessed using correlation analysis and linear regression analysis. Results: The prevalence of cognitive deficits among the patients in our study was 85.1% (74/87) which was much higher than that in the general population. According to correlation analysis, negative symptom was negatively correlated with speed of processing and social cognition, and general pathology showed a negative correlation with attention/vigilance. In addition, a positive correlation was found between age and speed of processing. No correlation was found between cognitive deficits and positive symptom. Conclusions: This study confirmed that negative symptom is negatively related with some domains of cognitive function in first-episode drug naïve schizophrenia patients. Trail Registration: NCT03451734. Registered March 2, 2018 (retrospectively registered).

Theta activity from frontopolar cortex, mid-cingulate cortex and anterior cingulate cortex shows different roles in cognitive planning performance

Cognitive planning, the ability to develop a sequenced plan to achieve a goal, plays a crucial role in human goal-directed behavior. However, the specific role of frontal structures in planning is unclear. We used a novel and ecological task, that allowed us to separate the planning period from the execution period. The spatio-temporal dynamics of EEG recordings showed that planning induced a progressive and sustained increase of frontal-midline theta activity (FMθ) over time. Source analyses indicated that this activity was generated within the prefrontal cortex. Theta activity from the right mid-Cingulate Cortex (MCC) and the left Anterior Cingulate Cortex (ACC) were correlated with an increase in the time needed for elaborating plans. On the other hand, left Frontopolar cortex (FP) theta activity exhibited a negative correlation with the time required for executing a plan. Since reaction times of planning execution correlated with correct responses, left FP theta activity might be associated with efficiency and accuracy in making a plan. Associations between theta activity from the right MCC and the left ACC with reaction times of the planning period may reflect high cognitive demand of the task, due to the engagement of attentional control and conflict monitoring implementation. In turn, the specific association between left FP theta activity and planning performance may reflect the participation of this brain region in successfully self-generated plans.

Comparing the effect of the subcategories of atypical antipsychotic medications on cognition in schizophrenia using a meta-analytic approach

OBJECTIVES

The aim of this study was to compare the two most commonly prescribed classes of atypical antipsychotic medications (i.e., -pines and -dones) with regard to their effects on cognition in patients with schizophrenia.

DATA SOURCES

Ovid Technologies web-based software was used to search the Medline and PsycINFO computerized databases to identify articles that met the inclusion criteria.

REVIEW METHODS

The search was limited to papers published after 1990, written in English, employing human subjects, using atypical antipsychotics, using a within-subjects design or control group of patients with schizophrenia for comparisons, using participants aged from 18-65, and employing standardized neuropsychological measures.

RESULTS

A total of 996 eligible studies were identified, and of these 19 were finally analyzed. Nine domains of cognitive functioning were assessed. The two groups of agents produced equivalent overall effects (-dones = .254 versus -pines = .202). The -pines were found to improve the domains of attention/working memory, executive functioning, fluency, nonverbal memory, processing speed, and verbal memory, each with a significant, small effect size. The -dones were found to improve attention/working memory, executive functioning, motor function, nonverbal memory, processing speed, and verbal memory, each with a significant, small effect size. Failsafe N was robust for all of the domains for the -pines, but only for the verbal memory domain for the -dones, suggesting that the significant findings for the other domains with the -dones are more tenuous.

CONCLUSION

The results indicate that the agents were largely equivalent and that there was no clear evidence that the pattern of cognitive effects differed as a result of the agent applied. The effects themselves, while statistically significant, were small, indicating that some or all of the differences may be attributable to practice effects on the instruments employed.

Epigenetic signaling in schizophrenia

Histone modifications and DNA methylation represent central dynamic and reversible processes that regulate gene expression and contribute to cellular phenotypes. These epigenetic marks have been shown to play fundamental roles in a diverse set of signaling and behavioral outcomes. Psychiatric disorders such as schizophrenia and depression are complex and heterogeneous diseases with multiple and independent factors that may contribute to their pathophysiology, making challenging to find a link between specific elements and the underlying mechanisms responsible for the disorder and its treatment. Growing evidences suggest that epigenetic modifications in certain brain regions and neural circuits represent a key mechanism through which environmental factors interact with individual's genetic constitution to affect risk of psychiatric conditions throughout life. This review focuses on recent advances that directly implicate epigenetic modifications in schizophrenia and antipsychotic drug action.

Second-generation antipsychotic effect on cognition in patients with schizophrenia--a meta-analysis of randomized clinical trials

OBJECTIVE

To investigate the effect of second-generation antipsychotics on cognitive function in patients diagnosed with schizophrenia or schizoaffective disorder.

METHOD

Multiple-treatments meta-analysis model.

RESULTS

On cognitive composite score, sertindole was superior to clozapine, effect size (ES) 0.87; 95% CI: 0.12-1.63, quetiapine, ES 0.75; 95% CI: 0.00-1.49, and first-generation antipsychotics (FGAs), ES 0.89; 95% CI: 0.14-1.64. Analyses on each cognitive domain showed clozapine, ES 0.37; 95% CI: 0.00-0.74, olanzapine, ES 0.31; 95%CI: 0.02-0.59, quetiapine, ES 0.34; 95% CI: 0.03-0.64, and FGAs, ES 0.51; 95% CI: 0.18-0.83 performing poorer on verbal working memory than ziprasidone, as well as FGAs performing poorer than risperidone, ES 0.31; 95% CI: 0.04-0.58. On executive function, sertindole performed better than clozapine, ES 0.82; 95% CI: 0.06-1.58, olanzapine, ES 0.81; 95% CI: 0.07-1.55, quetiapine, ES 0.76; 95% CI: 0.02-1.51, ziprasidone, ES 0.90; 95% CI: 0.14-1.67, and FGAs, ES 0.83; 95% CI: 0.08-1.58. On processing speed, FGAs performed poorer than sertindole, ES 0.97; 95% CI: 0.02-1.91, and quetiapine, ES 0.36; 95% CI: 0.01-0.72. On long-term verbal working memory, clozapine performed poorer than olanzapine, ES 0.41; 95% CI: 0.06-0.76. On verbal fluency, FGAs performed poorer than olanzapine, ES 0.26; 95% CI: 0.01-0.50, and clozapine, ES 0.44; 95% CI: 0.06-0.81. Lastly, FGAs, ES 0.41; 95% CI: 0.04-0.78, and clozapine, ES 0.44; 95% CI: 0.05-0.83, performed poorer on visuospatial skill compared to olanzapine.

CONCLUSION

The meta-analysis was able to detect some trends in the data analyzed, but did not show any drug having a uniform positive cognitive profile.

Efficacy and safety of individual second-generation vs. first-generation antipsychotics in first-episode psychosis: a systematic review and meta-analysis

Because early treatment choice is critical in first-episode schizophrenia-spectrum disorders (FES), this meta-analysis compared efficacy and tolerability of individual second-generation antipsychotics (SGAs) with first-generation antipsychotics (FGAs) in FES. We conducted systematic literature search (until 12 December 2010) and meta-analysis of acute, randomized trials with ≥1 FGA vs. SGA comparison; patients in their first episode of psychosis and diagnosed with schizophrenia-spectrum disorders; available data for psychopathology change, treatment response, treatment discontinuation, adverse effects, or cognition. Across 13 trials (n = 2509), olanzapine (seven trials) and amisulpride (one trial) outperformed FGAs (haloperidol: 9/13 trials) in 9/13 and 8/13 efficacy outcomes, respectively, risperidone (eight trials) in 4/13, quetiapine (one trial) in 3/13 and clozapine (two trials) and ziprasidone (one trial) in 1/13, each. Compared to FGAs, extrapyramidal symptom (EPS)-related outcomes were less frequent with olanzapine, risperidone and clozapine, but weight gain was greater with clozapine, olanzapine and risperidone. Pooled SGAs were similar to FGAs regarding total psychopathology change, depression, treatment response and metabolic changes. SGAs significantly outperformed FGAs regarding lower treatment discontinuation, irrespective of cause, negative symptoms, global cognition and less EPS and akathisia, while SGAs increased weight more (p < 0.05-0.01). Results were not affected by FGA dose or publication bias, but industry-sponsored studies favoured SGAs more than federally funded studies. To summarize, in FES, olanzapine, amisulpride and, less so, risperidone and quetiapine showed superior efficacy, greater treatment persistence and less EPS than FGAs. However, weight increase with olanzapine, risperidone and clozapine and metabolic changes with olanzapine were greater. Additional FES studies including broader-based SGAs and FGAs are needed.

Long-term (3-year) neurocognitive effectiveness of antipsychotic medications in first-episode non-affective psychosis: a randomized comparison of haloperidol, olanzapine, and risperidone

INTRODUCTION

The initially postulated superior neurocognitive effectiveness of second-generation antipsychotics is currently under debate.

METHODS

A prospective, randomized, open-label study was carried out to compare the long-term neurocognitive effectiveness of haloperidol, olanzapine, and risperidone in the first episode of schizophrenia spectrum disorders. A final sample of 79 patients randomized to haloperidol (N = 28), olanzapine (N = 23), or risperidone (N = 28) who completed clinical and cognitive evaluations at baseline and 3-year follow-up was included in the final analysis. Forty-one healthy individuals were also included in the final analysis. The main outcome measure was cognitive changes at 3-year follow-up. Due to the fact that some of the patients had switched their initially prescribed antipsychotic medication during the course of the study (6 out of 28 in haloperidol group, 18 out of 23 in olanzapine group, and 24 out of 28 in risperidone group continued with the initial study drug at 3-year assessment), we have also conducted a per protocol analysis.

RESULTS

Overall, cognitive changes were similar in the three treatment groups and controls, although a greater improvement in Rey Auditory Verbal Learning Test, Digit Symbol, and Iowa Gambling Test was found in the treatment groups. The better performance observed on Rey Auditory Verbal Learning Test and Digit Symbol in olanzapine treatment group was likely explained by the lower prevalence of use of antimuscarinic drugs. These results were essentially similar to those found in the intention-to-treat analysis.

CONCLUSIONS

The major conclusion of this study is that haloperidol, olanzapine, and risperidone have not demonstrated substantial neurocognitive effectiveness, improving cognitive deficits present in the early phases of the illness. The study also underscores the importance of exploring new drugs for the treatment of cognitive impairments and associated functional disabilities in schizophrenia.

World Federation of Societies of Biological Psychiatry (WFSBP) Guidelines for Biological Treatment of Schizophrenia, part 1: update 2012 on the acute treatment of schizophrenia and the management of treatment resistance

These updated guidelines are based on a first edition of the World Federation of Societies of Biological Psychiatry Guidelines for Biological Treatment of Schizophrenia published in 2005. For this 2012 revision, all available publications pertaining to the biological treatment of schizophrenia were reviewed systematically to allow for an evidence-based update. These guidelines provide evidence-based practice recommendations that are clinically and scientifically meaningful and these guidelines are intended to be used by all physicians diagnosing and treating people suffering from schizophrenia. Based on the first version of these guidelines, a systematic review of the MEDLINE/PUBMED database and the Cochrane Library, in addition to data extraction from national treatment guidelines, has been performed for this update. The identified literature was evaluated with respect to the strength of evidence for its efficacy and then categorised into six levels of evidence (A-F; Bandelow et al. 2008b, World J Biol Psychiatry 9:242). This first part of the updated guidelines covers the general descriptions of antipsychotics and their side effects, the biological treatment of acute schizophrenia and the management of treatment-resistant schizophrenia.

Erythropoietin reverses the attentional set-shifting impairment in a rodent schizophrenia disease-like model

RATIONALE

Executive function impairment, as classically assessed using the Wisconsin Card Sort Test or intradimensional/extradimensional tests, is a key feature of schizophrenia but remains inadequately treated by existing therapies. Recently, however, erythropoietin has been shown to improve attentional set-shifting performance in schizophrenic patients.

OBJECTIVE

The present study utilized the rat intradimensional/extradimensional task to investigate the potential of erythropoietin to reverse a phencyclidine-induced extradimensional shift impairment when given alone or in combination with subchronic haloperidol treatment.

METHODS

Rats were subjected to a subchronic systemic administration (7 days, b.i.d) of either saline vehicle or phencyclidine (5 mg/kg) followed by a 7-day washout period during which haloperidol was given. Subsequently, rats were trained to dig in baited bowls for a food reward and to discriminate on the basis of digging media or bowl odor. In experiment 1, rats performed a series of discriminations following acute administration of vehicle, erythropoietin, or modafinil. In a second experiment, rats receiving either haloperidol in the drinking water or just normal drinking water were run in the attentional set-shifting task after acute administration of erythropoietin (1,000 or 10,000 IU/ml  i.p., selected from experiment 1).

RESULTS

The subchronic phencyclidine-induced extradimensional deficit was ameliorated by both erythropoietin and modafinil. When combined with subchronic haloperidol, the higher dose of erythropoietin tested was able to reverse the extradimensional shift impairment.

CONCLUSIONS

Overall, these findings further support the use of erythropoietin as an adjunct to antipsychotic therapy in order to address, at least part of, the cognitive dysfunction associated with schizophrenia.

Efficacy of atypical v. typical antipsychotics in the treatment of early psychosis: meta-analysis

BACKGROUND

There is an ongoing debate about the use of atypical antipsychotics as a first-line treatment for first-episode psychosis.

AIMS

To examine the evidence base for this recommendation.

METHOD

Meta-analyses of randomised controlled trials in the early phase of psychosis, looking at long-term discontinuation rates, short-term symptom changes, weight gain and extrapyramidal side-effects. Trials were identified using a combination of electronic (Cochrane Central, EMBASE, MEDLINE and PsycINFO) and manual searches.

RESULTS

Fifteen randomised controlled trials with a total of 2522 participants were included. No significant differences between atypical and typical drugs were found for discontinuation rates (odds ratio (OR) = 0.7, 95% CI 0.4 to 1.2) or effect on symptoms (standardised mean difference (SMD) = -0.1, 95% CI -0.2 to 0.02). Participants on atypical antipsychotics gained 2.1 kg (95% CI 0.1 to 4.1) more weight than those on typicals, whereas those on typicals experienced more extrapyramidal side-effects (SMD = -0.4, 95% CI -0.5 to -0.2).

CONCLUSIONS

There was no evidence for differences in efficacy between atypical and typical antipsychotics, but there was a clear difference in the side-effect profile.

Cognitive effectiveness of olanzapine and risperidone in first-episode psychosis

BACKGROUND

Cognitive impairment in schizophrenia-spectrum disorders is highly prevalent and notably influences functional outcomes.

AIMS

To characterise the cognitive effectiveness of second-generation antipsychotic drugs.

METHOD

One hundred consecutive and previously unmedicated patients with first-episode schizophrenia-spectrum disorders were admitted. Seventy-seven completed baseline, 1-month and 6-month psychopathological and neuropsychological assessments. Patients were randomised to risperidone or olanzapine treatment. Four final treatment allocation groups were defined since patients continued treatment in their normal setting: risperidone, olanzapine, mixed and no-antipsychotic groups.

RESULTS

There were no differences in cognitive effectiveness between the four treatment groups. Reliable change index methods demonstrated that nearly a half of patients showed an improvement in Global Cognitive Score at the 6-month assessment. Improvement on the neuropsychological tests ranged from 17 to 54%. A strong predictor of cognitive response was poor performance on baseline neuropsychological tests; response was moderately influenced by a low premorbid scholastic performance and IQ.

CONCLUSIONS

Cognitive improvement related to second-generation antipsychotic drugs appeared within the first 4 weeks of treatment and persisted at 6 months irrespective of treatment group. Greater cognitive dysfunction at baseline and lower premorbid cognitive background predicted cognitive improvement in our sample.

Neurocognitive functions in euthymic bipolar patients

OBJECTIVE

Meta-analytic findings support the hypothesis of specific neurocognitive deficits for bipolar patients in the domains of attention, processing speed, memory and executive functions. This study aims to show neurocognitive impairment in euthymic patients with bipolar I disorder compared with healthy controls while detailing the impact of medication side-effects or illness characteristics on neuropsychological test performance.

METHOD

Forty euthymic patients with bipolar I disorder were compared with 40 healthy controls in a cross-sectional design. Clinical features and neuropsychological measures of IQ, psychomotor speed, verbal fluency, learning and memory, executive functions and attention were assessed.

RESULTS

Patients without antipsychotic drug use did not differ significantly from healthy controls in any neuropsychological measure. Yet patients treated with antipsychotics showed significant underperformance in the domains of semantic fluency, verbal learning and recognition memory as well as executive functions related to planning abilities, even when clinical features were controlled for.

CONCLUSION

The impact of antipsychotic medication needs to be further clarified for euthymic bipolar patients and should be considered when neuropsychological test performance is interpreted.

Relative contribution of antipsychotics, negative symptoms and executive functions to social functioning in stable schizophrenia

The purpose of this study was to examine the relative contributions of antipsychotic medication, negative symptoms and executive functions to impairment in social functioning in a sample of outpatients with stable schizophrenia. One-hundred and sixty-eight consecutive outpatients with stable schizophrenia were enrolled in a cross-sectional study. We performed a path analysis using multiple regression technique in order to assess the specific effect of antipsychotic type (first-generation antipsychotics versus second-generation antipsychotics) on social functioning and the possible mediating role of executive functions and negative symptoms. Our findings suggested that (i) second generation antipsychotics (SGAs) use predicted better social functioning (Beta=.24, p=.003) and better executive functions (Beta=.25, p=.003); conversely SGAs use was not associated with lesser negative symptoms (Beta=.00, p=.981); (ii) impaired executive functions and severity of negative symptoms were associated with worse social functioning (Beta=.19, p=.016; Beta=.28, p=.001); (iii) when we inserted in the model Positive and Negative Syndrome Scale - Negative Symptom subscale (PANSS-N) and Wisconsin Card Sorting Test - number of achieved sorting categories (WCST-cat), the former failed to show a mediation effect, while the latter seemed to mediate partially the effect of SGAs on social functioning. Taken together, the present results suggest that it is critical to examine individually executive functions and negative symptoms because they seem to relate to social functioning in different and independent ways and thus might represent separable treatment targets. Furthermore, social functioning appears a complex outcome multiply determined with no single predictor variable explaining a sufficient amount of variance.

Cognitive and psychomotor effects of risperidone in schizophrenia and schizoaffective disorder

OBJECTIVE

The aim of this review was to discuss data from double-blind, randomized controlled trials (RCTs) that have investigated the effects of oral and long-acting injectable risperidone on cognitive and psychomotor functioning in patients with schizophrenia or schizoaffective disorder.

METHODS

PubMed/MEDLINE and the Institute of Scientific Information Web of Science database were searched for relevant English-language double-blind RCTs published between March 2000 and July 2008, using the terms schizophrenia, schizoaffective disorder, cognition, risperidone, psychomotor, processing speed, attention, vigilance, working memory, verbal learning, visual learning, reasoning, problem solving, social cognition, MATRICS, and long-acting. Relevant studies included patients with schizophrenia or schizoaffective disorder. Cognitive domains were delineated at the Consensus Conferences of the National Institute of Mental Health-Measurement And Treatment Research to Improve Cognition in Schizophrenia (NIMH-MATRICS). The tests employed to assess each domain and psychomotor functioning, and the within-group and between-group comparisons of risperidone with haloperidol and other atypical antipsychotics, are presented. The results of individual tests were included when they were individually presented and interpretable for either drug; outcomes that were presented as cluster scores or factor structures were excluded.

RESULTS

A total of 12 articles were included in this review. Results suggested that the use of oral risperidone appeared to be associated with within-group improvements on the cognitive domains of processing speed, attention/vigilance, verbal and visual learning and memory, and reasoning and problem solving in patients with schizophrenia or schizoaffective disorder. Risperidone and haloperidol seemed to generate similar beneficial effects (on the domains of processing speed, attention/vigilance, [verbal and nonverbal] working memory, and visual learning and memory, as well as psychomotor functioning), although the results for verbal fluency, verbal learning and memory, and reasoning and problem solving were not unanimous, and no comparative data on social cognition were available. Similar cognitive effects were found with risperidone, olanzapine, and quetiapine on the domains of verbal working memory and reasoning and problem solving, as well as verbal fluency. More research is needed on the domains in which study results were contradictory. For olanzapine versus risperidone, these were verbal and visual learning and memory and psychomotor functioning. No comparative data for olanzapine and risperidone were available for the social cognition domain. For quetiapine versus risperidone, the domains in which no unanimity was found were processing speed, attention/vigilance, nonverbal working memory, and verbal learning and memory. The limited available reports on risperidone versus clozapine suggest that: risperidone was associated with improved, and clozapine with worsened, performance on the nonverbal working memory domain; risperidone improved and clozapine did not improve reasoning and problem-solving performance; clozapine improved, and risperidone did not improve, social cognition performance. Use of long-acting injectable risperidone seemed to be associated with improved performance in the domains of attention/vigilance, verbal learning and memory, and reasoning and problem solving, as well as psychomotor functioning. The results for the nonverbal working memory domain were indeterminate, and no clear improvement was seen in the social cognition domain. The domains of processing speed, verbal working memory, and visual learning and memory, as well as verbal fluency, were not assessed.

CONCLUSIONS

The results of this review of within-group comparisons of oral risperidone suggest that the agent appeared to be associated with improved functioning in the cognitive domains of processing speed, attention/vigilance, verbal and visual learning and memory, and reasoning and problem solving in patients with schizophrenia or schizoaffective disorder. Long-acting injectable risperidone seemed to be associated with improved functioning in the domains of attention/vigilance, verbal learning and memory, and reasoning and problem solving, as well as psychomotor functioning, in patients with schizophrenia or schizoaffective disorder.

Chronic nicotine and dizocilpine effects on nicotinic and NMDA glutamatergic receptor regulation: interactions with clozapine actions and attentional performance in rats

Blockade of NMDA glutamate receptors with dizocilpine (MK-801) has been shown to cause substantial cognitive deficits and has been used to model symptoms of schizophrenia. Nicotine or nicotinic agonists, in contrast, may enhance cognitive or attentional functions and be of therapeutic potential in schizophrenia. Nicotinic-glutamatergic interactions, therefore, may have important implications in cognitive functions and antipsychotic treatments. Clozapine, a widely used antipsychotic drug, has been shown in some studies to be effective in ameliorating the cognitive deficits associated with schizophrenia. However, there is some evidence to suggest that clozapine similar to haloperidol may impair sustained attention in rats. In this study, we sought to determine whether chronic nicotine or dizocilpine may modify the effects of acute clozapine on attentional parameters and whether the behavioral effects would correlate with nicotinic or NMDA receptor densities in discrete brain regions. Adult female rats trained on an operant visual signal detection task were given 4 weeks of nicotine (5 mg/kg/day), dizocilpine (0.15 mg/kg/day), the same doses of both nicotine and dizocilpine as a mixture, or saline by osmotic minipump. While on chronic treatment, rats received acute injections of various doses of clozapine (0, 0.625, 1.25, 2.5 mg/kg, sc) 10 min prior to tests on attentional tasks. The pumps were removed on day 28 and 24 h later the animals were sacrificed for measurements of receptor densities in specific brain regions. The percent correct hit as a measure of sustained attention was significantly impaired by clozapine in a dose-related manner. Neither chronic nicotine nor dizocilpine affected this measure on their own or modified the effects of clozapine. Both nicotine and dizocilpine affected the receptor bindings in a region specific manner and their combination further modified the effects of each other in selective regions. Attentional performance was inversely correlated with alpha-bungarotoxin binding in the frontal cortex only. In conclusion, the data suggest attentional impairments with clozapine alone and no modification of this effect with nicotine or dizocilpine. Moreover, cortical low affinity nicotinic receptors may have a role in attentional functions.