A Canadian multicenter trial assessing memory and executive functions in patients with schizophrenia spectrum disorders treated with olanzapine

Ameliorating schizophrenia-like symptoms in vasopressin deficient male Brattleboro rat by chronic antipsychotic treatment

Due to its various function vasopressin has been associated with many psychiatric disorders, including schizophrenia. Our previous study confirmed that vasopressin-deficient (di/di) Brattleboro rat can be a good genetic model for schizophrenia. Our present aim was to confirm whether the treatment effects of marketed antipsychotics are similar in di/di rats to those seen in human schizophrenic patients. Chronic subcutaneous administration of aripiprazole (5 mg/kg), clozapine (1 mg/kg), haloperidol (0.1 mg/kg), olanzapine (0.3 mg/kg) or risperidone (0.25 mg/kg) was used for 15 days in control (+/+ Brattleboro) and di/di rats. Social discrimination, social avoidance and prepulse inhibition tests were conducted on day 1, 8 and 15 of the treatment. Vasopressin-deficient rats showed social memory- and sensorimotor gating deficit. All used antipsychotics successfully normalized the reduced prepulse inhibition of di/di animals. However, most were effective only after prolonged treatment. Aripiprazole, clozapine, and olanzapine normalized the social memory deficit, while the effects of haloperidol and risperidone were not unequivocal. All drugs reduced social interest to some extent both in control and in di/di animals, aripiprazole being the less implicated in this regard during the social avoidance test. The restoration of schizophrenia-like behavior by antipsychotic treatment further support the utility of the vasopressin-deficient Brattleboro rat as a good preclinical model. Reduced social interest might be a general side-effect of antipsychotics, and aripiprazole has the most favorable profile in this regard.

Glutamate receptor 1 phosphorylation at serine 845 contributes to the therapeutic effect of olanzapine on schizophrenia-like cognitive impairments

Schizophrenia patients exhibit a wide range of impairments in cognitive functions. Clinically, atypical antipsychotic drugs (AAPs) such as olanzapine (OLZ) have a therapeutic effect on memory function among schizophrenia patients rather than typical antipsychotics, e.g., haloperidol. To date, however, little is known about the neuroplasticity mechanism underlying the effect of AAPs on the impairment of cognitive functions. Here, we treated schizophrenia rat models with a systematic injection of MK-801 (0.1mg/kg) and chose the drug OLZ as a tool to investigate the mechanisms of AAPs when used to alter cognitive function. The results showed that the systematic administration of MK-801 results in the impairment of spatial learning and memory as well as spatial working memory in a Morris water maze task. OLZ but not HAL improved these MK-801-induced cognitive dysfunctions. After MK-801 application, the hippocampal LTP was profoundly impaired. In conjunction with the results of the behavioral test, the administration of OLZ but not of HAL resulted in a significant reversal effect on the impaired LTP induced via MK-801 application. Furthermore, we found that OLZ but not HAL can upregulate the phosphorylation of GluR1 Ser845. These data suggest that the therapeutic effect of OLZ on cognitive dysfunctions may be due to its contribution to synaptic plasticity via the ability to upregulate the state of GluR1 Ser845 phosphorylation. We therefore suggest that the upregulated state of GluR1 Ser845 phosphorylation may be a promising target for developing novel therapeutics for treating schizophrenia.

Information for physicians and pharmacists about drugs that might cause dry mouth: a study of monographs and published literature

BACKGROUND

Over three-quarters of the older population take medications that can potentially cause dry mouth. Physicians or pharmacists rarely inform patients about this adverse effect and its potentially severe damage to the teeth, mouth and general health.

OBJECTIVES

The objectives of this study were to (1) identify warnings in the literature about dry mouth associated with the most frequently prescribed pharmaceutical products in Canada; and (2) consider how this information might be obtained by physicians, pharmacists and patients.

METHODS

Monographs on the 72 most frequently prescribed medications during 2010 were retrieved from the Compendium of Pharmaceuticals and Specialties (CPS, a standard drug information reference for physicians and pharmacists), the National Library of Medicine's 'DailyMed' database, directly from the manufacturers, and from a systematic search of biomedical journals.

RESULTS

The CPS provided monographs for 43% of the medications, and requests to manufacturers produced the remaining monographs. Mentions of dry mouth were identified in 61% of the products (43% amongst CPS monographs; an additional 43% amongst manufacturers' monographs; 7% in the DailyMed database and 7% from biomedical journals); five medications had contradictory reports in different monographs.

CONCLUSION

Nearly two-thirds (61%) of the most commonly prescribed medications can cause dry mouth, yet warnings about this adverse effect and its potentially serious consequences are not readily available to physicians, pharmacists, dentists or patients.

A randomized controlled trial of olanzapine improving memory deficits in Han Chinese patients with first-episode schizophrenia

Olanzapine is an atypical antipsychotic for the treatment of schizophrenia, in which memory impairment is a core deficit. The methods of positive and negative syndrome scale (PANSS), Wechsler memory scale-4th edition (WMS-IV) and event-related potential (ERP) were used to study the effects of olanzapine on the cognitive function in the first-episode schizophrenic patients. We performed multicentre, randomized, double-blind, placebo-controlled, parallel-group clinical trial to study the cognitive functioning in Han Chinese first-episode schizophrenic patients in a 12-week treatment regime with olanzapine (129 cases) or placebo (132 cases). The results showed that (1) the patients with first-episode schizophrenia showed significant deficits in the long-term memory, short-term memory, immediate memory and memory quotient by WMS-IV assessment, and decreases the total scores, positive symptoms, negative symptoms and general psychopathology by PANSS assessment; (2) olanzapine could significantly improve the PANSS scores including total scores, positive symptoms, negative symptoms and general psychopathology in the first-episode schizophrenic patients; (3) olanzapine could significantly improve the short-term memory, immediate memory and memory quotient in the first-episode schizophrenic patients; and (3) although the latencies of P(2), N(2) and P(3) were significantly prolonged, P(2) and P(3) amplitudes were decreased and the latencies of N(1) did not change, olanzapine did not influence any P(300) items in the first-episode schizophrenic patients. The data suggested that that olanzapine could improve cognitive process, such as memorizing and extraction of the information although there were many changes of cognitive functions in Han Chinese first-episode schizophrenic patients.

Predictors of quality of life in inpatients with schizophrenia

Shortening hospital stays has become a key focus in psychiatric care in recent years. However, patients with schizophrenia account for about 60% of inpatients in psychiatry departments in Japan. This study was designed to investigate the relationship between quality of life (QOL) and key indicators for long-term hospital stays among schizophrenia inpatients. A further aim was to elucidate the clinical determinants of QOL among long-stay inpatients. The study sample consisted of 217 inpatients with schizophrenia. Age, duration of illness, duration of hospitalization, years of education, body mass index, neurocognitive function, drug-induced extrapyramidal symptoms, involuntary movements, psychiatric symptoms, and dose equivalents of antipsychotics and anticholinergic agents were used as index factors. Pearson linear correlation and regression analyses were performed to examine the associations between QOL and the above-mentioned factors. Negative symptoms, psychological discomfort, and resistance as rated on the Brief Psychiatric Rating Scale (BPRS) were correlated with all subscale scores of the Japanese version of the Schizophrenia Quality of Life Scale (JSQLS). Stepwise regression showed that negative symptoms, psychological discomfort, and resistance predicted the dysfunction of psycho-social activity score and the dysfunction of motivation and energy score on the JSQLS. This study shows that active treatment for negative symptoms, psychological discomfort, and resistance should be recommended to improve QOL among inpatients with schizophrenia.

Evaluation of efficacy, safety, and cognitive profile of amisulpride per se and its comparison with olanzapine in newly diagnosed schizophrenic patients in an 8-week, double-blind, single-centre, prospective clinical trial

Background. Impaired cognitive functions in schizophrenia are the major deciding factors in response to treatment. Conventional antipsychotics have minimal impact on cognitive dysfunctions and are associated with adverse effects. Atypical antipsychotics have shown promise in treatment of cognitive and negative symptoms of schizophrenia. Efforts are underway to find out the best drug amongst atypical antipsychotics. Objective. To compare efficacy, safety, and cognitive profile of amisulpride and olanzapine in the treatment of acute psychotic exacerbations of schizophrenia. Method. A prospective, randomized, double-blind, single-center, 8-week clinical trial we used. Subjects and Treatments. Seventy four patients were treated for two months with either amisulpride (400-800 mg/d) or olanzapine (10-20 mg/d). Statistics. Mann Whitney U test we used for independent samples with P < 0.05 taken as significant. Results. Brief psychiatric rating scale (BPRS) was used as a primary measure of efficacy. Other measures of efficacy and safety were also evaluated. Both amisulpride and olanzapine groups showed equivalent improvement in psychotic symptoms on BPRS scale. Less than five percent of patients suffered adverse effects only to withdraw from the study. Olanzapine group showed statistically significant (P < 0.05) weight gain compared with amisulpride group. Amisulpride group showed significant improvement (P < 0.05) in various cognitive parameters as compared to olanzapine group.

A transdisciplinary perspective of chronic stress in relation to psychopathology throughout life span development

The allostatic load (AL) model represents an interdisciplinary approach to comprehensively conceptualize and quantify chronic stress in relation to pathologies throughout the life cycle. This article first reviews the AL model, followed by interactions among early adversity, genetics, environmental toxins, as well as distinctions among sex, gender, and sex hormones as integral antecedents of AL. We next explore perspectives on severe mental illness, dementia, and caregiving as unique human models of AL that merit future investigations in the field of developmental psychopathology. A complimenting transdisciplinary perspective is applied throughout, whereby we argue that the AL model goes beyond traditional stress–disease theories toward the advancement of person-centered research and practice that promote not only physical health but also mental health.

Cognitive efficacy of quetiapine and olanzapine in early-onset first-episode psychosis

The primary purpose of this study was to compare changes in cognition in early-onset psychosis after 6-months treatment with quetiapine or olanzapine. This is a randomized, single-blind, 6-month study in 50 adolescents with a diagnosis of early-onset psychosis. Patients were randomized to quetiapine (n = 24) or olanzapine (n =26). A thorough neuropsychological battery was administered at baseline and after 6-month treatment. Out of the total sample included in the study, 32 patients completed at least 6-months treatment with the assigned medication (quetiapine, n =16; olanzapine, n = 16). No changes were observed in cognitive performance after 6-month treatment with quetiapine or olanzapine. Although some trends toward cognitive improvement were observed for the olanzapine group after 6-month treatment, neither group showed statistically significant gains. Furthermore, there was no evidence of any differential efficacy of olanzapine or quetiapine on cognitive improvement in this sample of adolescents with psychosis.

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.

Longitudinal studies of cognition in schizophrenia: meta-analysis

BACKGROUND

A wide range of cognitive deficits have been demonstrated in schizophrenia, but their longitudinal course remains unclear.

AIMS

To bring together all the available information from longitudinal studies of cognitive performance in people with schizophrenia.

METHOD

We carried out a meta-analysis of 53 studies. Unlike previous reviewers, we included all studies (regardless of the type of medication), analysed each variable separately and compared results with data from controls.

RESULTS

Participants with schizophrenia showed a significant improvement in most cognitive tasks. The available data for controls showed, with one exception (the Stroop test), a similar or greater improvement. Performance in semantic verbal fluency remained stable in both individuals with schizophrenia and controls.

CONCLUSIONS

Participants with schizophrenia displayed improvement in most cognitive tasks, but practice was more likely than cognitive remediation to account for most of the improvements observed. Semantic verbal fluency may be the best candidate cognitive endophenotype.

Treatment with amisulpride and olanzapine improve neuropsychological function in schizophrenia

OBJECTIVES

Although antipsychotic drugs control acute psychotic manifestations of schizophrenia, improving cognitive symptoms is also important for long-term prognosis.

METHODS

Three hundred and seventy-seven adult patients with acute psychosis were randomised to either amisulpride (200-800 mg/d) or olanzapine (5-20 mg/d) for 6 months. Neuropsychological performance was assessed at inclusion and after 6 months in a subgroup of 26 subjects (11 treated with amisulpride and 15 with olanzapine) using the Auditory Verbal Learning Test (AVLT), the Trail Making Test (TMT) and the Controlled Oral Word Association Test (COWAT).

RESULTS

The improvement in BPRS score was similar in both treatment groups. No significant differences in test performance between groups were observed at inclusion. After 6 months, AVLT scores increased by 8.7 points in the amisulpride group and by 2.3 points in the olanzapine group (p = 0.049). Completion speed in the TMT increased by 17.4 s (amisulpride) and 15.4 s (olanzapine) for Part A and by 39.8 and 48.8 s, respectively for Part B. Performance in the COWAT improved little in both groups.

CONCLUSIONS

Both amisulpride and olanzapine produce sustained improvement in certain measures of neuropsychological performance in patients with schizophrenia; a significant improvement in score on the AVLT was observed only with amisulpride.

The neurocognitive effects of aripiprazole: an open-label comparison with olanzapine

RATIONALE

Cognitive deficits are a core feature of schizophrenia. As a target of intervention, improvements in cognition may lead to improvements in functional outcome.

OBJECTIVES

The present paper is the first report, to our knowledge, on the neurocognitive effects of aripiprazole. Unlike other second-generation antipsychotics, aripiprazole is a D(2) and D(3) receptor partial agonist. It is unknown what effects this unusual pharmacological profile may yield on neurocognition.

MATERIALS AND METHODS

The present open-label study included data on 169 patients with schizophrenia or schizoaffective disorder who were randomly treated with aripiprazole or olanzapine. Subjects received a neurocognitive battery at baseline, week 8, and 26.

RESULTS

The aripiprazole group had a significantly greater dropout rate than the olanzapine group. Neurocognitive data were reduced through a principal components analysis that yielded a three-factor solution. The factors were general cognitive functioning, executive functioning, and verbal learning. For general cognitive functioning, both groups improved from baseline and the effects were relatively stable over the 26-week protocol. There were no differential treatment effects. For executive functioning, neither group improved significantly from baseline. For verbal learning, the aripiprazole group improved significantly from baseline to the 8th and 26th week of assessment, and there was a between-group effect favoring aripiprazole over olanzapine that was largely attributable to the differences in performance within the 8th week. Separate analyses were conducted for a measure of sustained attention (Continuous Performance Test-Identical Pairs). There were no differential treatment effects on this measure.

CONCLUSIONS

The findings from this open-label study suggest that the neurocognitive effects of aripiprazole are at least as good as those of olanzapine.

Cognition, schizophrénie et effet des antipsychotiques : le point de vue d’un laboratoire de recherche clinique

BACKGROUND

In this review, we conclude that cognitive impairments are as important as positive and negative symptoms in the clinical assessment and management of patients with schizophrenia. This is not a comprehensive review, considering that the new Measurement And Treatment Research to Improve Cognition in Schizophrenia (MATRICS) model will soon provide valuable data. It is however a product of the collective efforts of a French Canadian clinical research team that proposes a synthesis of data of pragmatic interest to clinicians. Medication with improved safety and cognition profile, gene-rally lead to better outcomes by facilitating compliance with drug regimens and rehabilitation programs. In addition, measures of attention and executive function (EF) appear to improve with novel antipsychotics when compared to traditional neuroleptics. Nevertheless, evaluating cognitive performance is not a routine procedure outside the domain of research. For example, procedural learning (PL) -- an important measure of cognitive function -- refers to cognitive and motor learning processes in which execution strategies cannot be explicitly described (ie learning by doing). These actions or procedures are then progressively learned through trial and error until automation of optimal performance is established. Procedural learning is rarely assessed in clinical practice. Inconsistent findings regarding the effects of neuroleptic drugs on PL have been reported.

LITERATURE FINDINGS

Trials using acute administration of chlorpromazine in normal subjects induced PL deficits, suggesting the direct effect of neuroleptics, presumably via a D(2) dopamine blockade in the striatum. In a recent study by our group, schizophrenia patients, divided into three groups according to their pharmacological treatment (haloperidol, clozapine and risperidone) were compared to normal controls on two PL tasks; a visuomotor learning task (mirror drawing) and a problem solving learning task (Tower of Toronto). No deficits were detected in patients receiving clozapine, while haloperidol was associated with deleterious effects in both tasks. Risperidone, however, produced different effects depending on the task performed. Another 6-month double-blind Canadian study confirmed the beneficial effect of olanzapine on PL compared to haloperidol and risperidone. The differential effects of drugs on the striatal D(2) receptors, -irrespective of their classification as conventional or atypical neuroleptics and the specific process implicated in each of these PL tasks may explain these results. Tracer studies using radioactive benzamides (IBZM) specific to striatal D receptors determined a relationship between striatal D(2) receptor occupancy and PL performance such as the mirror drawing task. Using this method, data obtained in Montreal on schizophrenia patients receiving olanzapine and haloperidol have shown that the coefficient of determination in a visuomotor PL task varied inversely with D2 receptor saturation.

DISCUSSION

This review probes the effect of impaired cognitive functions on schizophrenia patients' quality of life. Cognitive deficits found in schizophrenia affect planning, along with the aptitude to initiate and -regulate a goal-directed behaviour. These impairments have been repeatedly, yet inconclusively, attributed to frontal lobe dysfunction. Morphological findings obtained from neuroimaging studies remain inconsistent, some noting no differences between patients and controls while others observing reduced prefrontal volumes in schizophrenia patients. Conversely, functional neuroimaging (fMRI) demonstrated reduced frontal blood flow relative to global cerebral perfusion in schizophrenia patients. Overall, neuroimaging literature provides reliable evidence of frontal impairments in schizophrenia, although the average magnitude of difference between patients and controls is insufficient to defend a frontal lobe dysfunction hypo-thesis, as far as brain volume, resting cerebral metabolism or blood flow are concerned. The only measurement clearly distinguishing between patients and controls is fMRI of the frontal lobe while performing an experimentally controlled task. Here, schizophrenia patients fail to activate their frontal cortex when required. Sensitive to frontal lobe dysfunction are Neuropsychological tests of executive function.

STUDY DESIGN

A study conducted in Montreal assessed the relation between EF impairments and difficulties in planning daily activities in schizophrenia patients scoring more than 3 on at least 4 items of the PANSS negative subscale. Performances on EF, memory and script generation were measured and compared to controls. Script production task required that subjects recite 10-20 actions that would normally be carried out for during daily life activity (going to a restaurant, buying groceries, etc.). Patients' performances were significantly lower with higher perserveration and sequencing impairments. Routine activities such as the ability to cook a meal were similarly investigated. Patients were videotaped in a kitchen while preparing a specific meal.

RESULTS

Optimal sequence of micro- and macro-steps necessary to prepare the meal in a minimal time were measured. Sequencing errors, repetitions and omissions were significantly higher compared to controls. In addition, temporal organization was positively correlated with negative symptoms and low EF performance on neuro-psychological tasks. Thus concluding that EF impairment interferes with basic routine activities in schizophrenia patients, notably those with negative symptoms. Last but not least, we assessed the progress of patients' subjective complaints with regards to their cognitive functions using tests such as the SSTICS, specifically developed to address subjective cognitive complaints and insight.

CONCLUSION

This review concludes that from now on cognitive deficit should be recognized as a major element in social and professional integration of schizophrenia patients, and should become a standardized assessment approach in clinical practice.

Cognitive dysfunctions in medicated and unmedicated patients with recent-onset schizophrenia

Schizophrenia is associated with impairments in many cognitive domains on which the influence of antipsychotics, whether conventional or atypical, remains unclear. We conducted a study of recent-onset schizophrenic patients (DSM IV) that included unmedicated (n=19), and medicated (n=19) patients matched for age and IQ. Both groups of patients had comparably low extra-pyramidal symptoms (EPS). Cognitive tasks included attentional tasks (alertness and divided attention tests), a working memory task (a verbal n-back test) and the Wisconsin Card Sorting Test (WCST). After adjustment for the Total PANSS score, we found no significant difference between the two groups of patients in any of the cognitive tasks. When compared to a group of healthy controls (n=20) matched for IQ level, unmedicated patients performed significantly worse in all cognitive tasks, with significantly longer reaction times for alertness, divided attention and working memory. These results confirm the presence of cognitive impairments in attentional and executive functions in recent-onset patients whether or not they are medicated. There was no evidence that either conventional or atypical antipsychotics had an influence on patients when EPS were excluded. Altogether, our results further support the idea that cognitive deficits in schizophrenia are enduring features per se and cannot be considered as secondary to psychiatric symptoms or to the adverse effects of medication. In addition our results suggest that antipsychotics do not have a major effect on these impairments.

Current therapy issues and unmet clinical needs in the treatment of schizophrenia: a review of the new generation antipsychotics

This review discusses the atypical antipsychotics, focusing on the possibility of symptom reduction with a minimum of side-effects. A selective review of clinically relevant reports, studies and meta-analyses is presented. The results from clinical trials suggest that atypical agents improve negative and affective symptoms, and cognitive functioning more than typical antipsychotics, but that the pattern of effects on these domains, as well as on suicidality, appears to differ. In clinical trials, the newer drugs generally have less extrapyramidal side-effects (EPS) than typical antipsychotics. However, amisulpride, risperidone, olanzapine and ziprasidone still show evidence of a dose-related increase in EPS, whereas clozapine, quetiapine, sertindole and aripiprazole do not. Weight gain, increased blood lipids/cholesterol, and insulin resistance/type 2 diabetes are emerging as significant treatment-associated concerns, particularly for clozapine and olanzapine. Sedation has been reported for all the newer compounds except sertindole. The considerable variation in benefit/risk profiles of the atypical compounds can help the clinician to select the most appropriate treatment for individual patients.

On the trail of a cognitive enhancer for the treatment of schizophrenia

The aim of this critical review is to address that the study of cognition and antipsychotics is not always driven by logic and that research into real pro-cognitive drug treatments must be guided by a better understanding of the biochemical mechanisms underlying cognitive processes and deficits. Many studies have established that typical neuroleptic drugs do not improve cognitive impairment. Atypical antipsychotics improve cognition, but the pattern of improvement differs from drug to drug. Diminished cholinergic activity has been associated with memory impairments. Why atypical drugs improve aspects of cognition might lie in their ability to increase dopamine and acetylcholine in the prefrontal cortex. An optimum amount of dopamine activity in the prefrontal cortex is critical for cognitive functioning. Another mechanism is related to procedural learning, and would explain the quality of the practice during repeated evaluations with atypical antipsychotics due to a more balanced blockage of D2 receptors. Laboratory studies have shown that clozapine, ziprasidone, olanzapine, and risperidone all selectively increase acetylcholine release in the prefrontal cortex, whereas this is not true for haloperidol and thioridazine. A few studies have suggested that cholinomimetics or AChE inhibitors can improve memory functions not only in Alzheimer's disease but also in other pathologies. Some studies support the role of decreased cholinergic activity in the cognitive deficits while others demonstrate that decreased choline acetyltransferase activity is related to deterioration in cognitive performance in schizophrenia. Overall, results suggest the hypothesis that the cholinergic system is involved in the cognitive dysfunctions observed in schizophrenia and that increased cholinergic activity may improve these impairments. Furthermore, a dysfunction of glutamatergic neurotransmission could play a key role in cognitive deficits associated with schizophrenia. Further meta-analysis of various clinical trials in this field is required to account for matters on the grounds of evidence-based medicine.

Implications for Atypical Antipsychotics in the Treatment of Schizophrenia: Neurocognition Effects and a Neuroprotective Hypothesis

Cognitive impairment in schizophrenia occurs in the early phases of the disease and remains throughout its course. The basis for cognition lies in two main brain regions: the prefrontal cortex and hippocampus. Positron emission tomography, functional magnetic resonance imaging, and proton magnetic spectroscopy studies have shown that prefrontal cortex and hippocampus activity and cell density are lower in patients with schizophrenia than in healthy controls. Dopamine remains the fundamental neurotransmitter involved with schizophrenia. Catechol- O -methyltransferase accounts for about 60% of dopamine metabolism in the prefrontal cortex. Functional polymorphism for the catechol- O -methyltransferase genotypes has been identified in patients with schizophrenia. Those with the valine-valine genotype demonstrate rapid inactivation of dopamine, and performance in cognitive testing in patients is poorer with this allele than with other genotypes. N -methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate acid receptors are also strongly associated with cognitive impairment. Changes occur in apolipoproteins D and E, cholinesterase enzyme activity, neurotensin, and neural growth factors, leading to a possible neurodegenerative process and cognitive impairment in patients with schizophrenia. A fundamental link between psychosis and neurocognition probably arises from complex interactions between these systems at the intracellular secondary messenger system and with protein phosphorylation. Atypical antipsychotics evaluated in receptor models, cell cultures, and animal behavior paradigms indicate that these agents may provide neuroprotective effects. Clinical studies with atypical antipsychotics have consistently demonstrated improvement in cognitive symptoms, and such improvement appears to be correlated with improvement of negative symptoms. A neurodevelopmental model of cognitive impairment in schizophrenia aids in understanding why atypical antipsychotics improve cognitive symptoms.

Cognitive function and depression in symptom resolution in schizophrenia patients treated with an atypical antipsychotic

OBJECTIVE

To investigate which cognitive and affective features contribute most to responder/non-responder group separation during a switching trial with atypical antipsychotic.

DESIGN

A prospective open trial with an atypical antipsychotic (olanzapine).

PATIENTS

One hundred and thirty-four patients meeting diagnostic criteria for schizophrenia, schizophreniform or schizoaffective disorder began an 8-week open-label olanzapine treatment at a dose of 5 mg/day which was increased to 10 mg/day after one week.

INTERVENTIONS

Olanzapine during 8 weeks. Patients were considered as responders if their BPRS score decreased of at least 20% (n = 96) and non-responders if it did not (n = 38). Neuropsychological assessments were carried out at baseline, at four and at eight weeks.

RESULTS

Neurocognitive measures were analyzed for discriminate factors between responder and non-responder groups. A regression analysis was applied to explain the effects of depression on each cognitive variable. Depression was found to be a weak discriminant factor, however this finding could not firmly establish that depression is a potential factor in explaining deficits and improvements in cognition.