A comparison of the effect of clozapine with typical neuroleptics on cognitive function in neuroleptic-responsive schizophrenia

Long-Term Outcome of Clozapine in Treatment-Resistant Schizophrenia

PURPOSE/BACKGROUND

The favorable effect of clozapine on psychotic symptoms in patients with treatment-resistant (TR) schizophrenia (SCZ) in short-term studies is well established. However, prospective studies of the long-term outcome of clozapine treatment on psychopathology, cognition, quality of life, and functional outcome in TR-SCZ are limited.

METHODS/PROCEDURES

Here, we have examined the long-term (mean duration of follow-up 14 years) effects of clozapine on those outcomes in a prospective, open label study in 54 TR-SCZ patients. Assessments were performed at baseline, 6 weeks, 6 months, and at the last follow-up.

FINDINGS/RESULTS

Brief Psychiatric Rating Scale (BPRS) total, positive symptoms, and anxiety/depression at the last follow-up improved significantly from baseline, as well as from the 6-month evaluation ( P < 0.0001), with a 70.5% responder rate (≥20% improvement at the last follow-up from baseline). Quality of Life Scale (QLS) total improved by 72% at the last follow-up, with 24% of patients rated as having "good" functioning compared with 0% at baseline. Suicidal thoughts/behavior was significantly reduced at the last follow-up from the baseline. No significant change in negative symptoms was found at the last follow-up in the total sample. Short-term memory function declined at the last follow-up from baseline, but there was no significant change in processing speed. The QLS total showed a significant negative correlation with BPRS positive symptoms but not with cognitive measures, or negative symptoms, at the last follow-up.

IMPLICATIONS/CONCLUSIONS

For patients with TR-SCZ, improving psychotic symptoms with clozapine seems to have a more significant impact than negative symptoms or cognition on improving psychosocial function.

Connectivity Analyses of Bioenergetic Changes in Schizophrenia: Identification of Novel Treatments

We utilized a cell-level approach to examine glycolytic pathways in the DLPFC of subjects with schizophrenia (n = 16) and control (n = 16) and found decreased mRNA expression of glycolytic enzymes in pyramidal neurons, but not astrocytes. To replicate these novel bioenergetic findings, we probed independent datasets for bioenergetic targets and found similar abnormalities. Next, we used a novel strategy to build a schizophrenia bioenergetic profile by a tailored application of the Library of Integrated Network-Based Cellular Signatures data portal (iLINCS) and investigated connected cellular pathways, kinases, and transcription factors using Enrichr. Finally, with the goal of identifying drugs capable of "reversing" the bioenergetic schizophrenia signature, we performed a connectivity analysis with iLINCS and identified peroxisome proliferator-activated receptor (PPAR) agonists as promising therapeutic targets. We administered a PPAR agonist to the GluN1 knockdown model of schizophrenia and found it improved long-term memory. Taken together, our findings suggest that tailored bioinformatics approaches, coupled with the LINCS library of transcriptional signatures of chemical and genetic perturbagens, may be employed to identify novel treatment strategies for schizophrenia and related diseases.

Schizophrenia patients using atypical medication perform better in visual tasks than patients using typical medication

Schizophrenia (SCZ) patients show deficits in many domains, including cognition and perception. However, results are often mixed. One reason for mixed results may be differences in medication. Very little is known about the role of medication in visual processing. Here, we investigated the effects of typical vs. atypical medication on contrast sensitivity (spatial frequencies ranging from 0.2 to 20 cycles per degree), vernier acuity, and visual backward masking. From a large pool of patients, we selected 50 patients (Study 1, conducted in Brazil) and 97 patients (Study 2, conducted in Georgia) taking either only typical or atypical medication. Patients with atypical medication performed significantly better than patients with typical medication for contrast sensitivity, vernier duration, and backward masking. As a secondary result, we found similar, but not significant, trends for the cognitive tasks (Stroop, Flanker, Trail-Making Test-B, Wisconsin Card Sorting Test and Continuous Performance Test) in the same patients. No correlations were found between demographics, psychopathology, chlorpromazine equivalents and visual processing. A conclusion of our study is that one needs to be careful comparing studies when medication is not comparable.

Adolescent stress leads to glutamatergic disturbance through dopaminergic abnormalities in the prefrontal cortex of genetically vulnerable mice

BACKGROUND

Stress during the adolescent period influences postnatal maturation and behavioral patterns in adulthood. Adolescent stress-induced molecular and functional changes in neurons are the key clinical features of psychiatric disorders including schizophrenia.

OBJECTIVE

In the present study, we exposed genetically vulnerable mice to isolation stress to examine the molecular changes in the glutamatergic system involving N-methyl-d-aspartate (NMDA) receptors via dopaminergic disturbance in the prefrontal cortex (PFc).

RESULTS

We report that late adolescent stress in combination with Disrupted-in-Schizophrenia 1 (DISC1) genetic risk elicited alterations in glutamatergic neurons in the PFc, such as increased expression of glutamate transporters, decreased extracellular levels of glutamate, decreased concentration of d-serine, and impaired activation of NMDA-Ca2+/calmodulin kinase II signaling. These changes resulted in behavioral deficits in locomotor activity, forced swim, social interaction, and novelty preference tests. The glutamatergic alterations in the PFc were prevented if the animals were treated with an atypical antipsychotic drug clozapine and a dopamine D1 agonist SKF81297, which suggests that the activation of dopaminergic neurons is involved in the regulation of the glutamatergic system.

CONCLUSION

Our results suggest that adolescent stress combined with dopaminergic abnormalities in the PFc of genetically vulnerable mice induces glutamatergic disturbances, which leads to behavioral deficits in the young adult stage.

Comparative analysis of pharmacological properties of xanomeline and N-desmethylclozapine in rat brain membranes

BACKGROUND

3(3-Hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine (xanomeline) and N-desmethylclozapine are of special interest as promising antipsychotics with better efficacy, especially for negative symptoms and/or cognitive/affective impairment.

METHODS

The guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPγS) binding experiments were performed using (1) conventional filtration technique, (2) antibody-capture scintillation proximity assay, and (3) immunoprecipitation method, in brain membranes prepared from rat cerebral cortex, hippocampus, and striatum.

RESULTS

Xanomeline had agonistic activity at the M1 muscarinic acetylcholine receptor (mAChR) in all brain regions, as well as at the 5-HT1A receptor in the cerebral cortex and hippocampus. On the other hand, N-desmethylclozapine exhibited slight agonistic effects on the M1 mAChR, and agonistic properties at the 5-HT1A receptor in the cerebral cortex and hippocampus. This compound also behaved as an agonist at the δ-opioid receptor in the cerebral cortex and striatum. In addition, the stimulatory effects of N-desmethylclozapine on [(35)S]GTPγS binding to Gαi/o were partially mediated through mAChRs (most likely M4 mAChR subtype), at least in striatum.

CONCLUSIONS

The agonistic effects on the mAChRs (particularly M1 subtype, and also probably M4 subtype), the 5-HT1A receptor and the δ-opioid receptor expressed in native brain tissues, some of which are common to both compounds and others specific to either, likely shape the unique beneficial effectiveness of both compounds in the treatment for schizophrenic patients. These characteristics provide us with a clue to develop newer antipsychotics, beyond the framework of dopamine D2 receptor antagonism, that are effective not only on positive symptoms but also on negative symptoms and/or cognitive/affective impairment.

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.

Effect of alpha7 nicotinic acetylcholine receptor agonists on attentional set-shifting impairment in rats

RATIONALE

Attentional set shifting, a measure of executive function, is impaired in schizophrenia patients. Current standard of care has little therapeutic benefit for treating cognitive dysfunction in schizophrenia; therefore, novel drugs and animal models for testing novel therapies are needed. The NMDA receptor antagonist, MK-801, produces deficits in a rat maze-based set-shifting paradigm, an effect which parallels deficits observed on tests of executive function in schizophrenia patients. Alpha7 nicotinic acetylcholine receptor (nAChR) agonists, currently under clinical development by several companies, show promise in treating cognitive symptoms in schizophrenia patients and can improve cognition in various animal models.

OBJECTIVES

The objectives of the present study were to determine whether the MK-801 deficit in set shifting could be reproduced in a drug discovery setting and to determine whether cognitive improvement could be detected for the first time in this task with alpha7 nAChR agonists.

RESULTS

The data presented here replicate findings that a systemic injection of the NMDA receptor antagonist MK-801 can induce a deficit in set shifting in rats. Furthermore, the deficit could be reversed by the atypical antipsychotic clozapine as well as by several alpha7 nAch receptor agonists (SSR-180711, PNU-282987, GTS-21) with varying in vitro properties.

CONCLUSIONS

Results indicate that the MK-801 set-shift assay is a useful preclinical tool for measuring prefrontal cortical function in rodents and can be used to identify novel mechanisms for the potential treatment of cognitive deficits in schizophrenia.

Possible dose-side effect relationship of antipsychotic drugs: relevance to cognitive function in schizophrenia

Management of adverse events is a major concern of clinicians who use antipsychotic drugs. The incidence of motor side effects is dose dependent. Atypical antipsychotic drugs are less likely to induce neurologic side effects compared with typical (conventional) antipsychotics, such as haloperidol. Some recent, large-scale studies have shown that the incidence of metabolic side effects often associated with atypical agents does not differ among typical and atypical antipsychotics. Cognitive function, such as verbal learning memory, working memory, executive function, verbal fluency and attention/information processing, is the most influential determinant of outcome in patients with schizophrenia. Atypical antipsychotic drugs have been shown to be more efficacious in treating cognitive disturbances of schizophrenia compared with typical antipsychotic drugs. Serotonin (5-hydroxytryptamine [5-HT]) receptor subtypes, such as the 5-HT1A receptor, are considered to mediate the ability of antipsychotic drugs to enhance cognition. On the other hand, treatment with some atypical agents, such as risperidone, may deteriorate working memory in some people with early-stage schizophrenia. The paradoxical side effects of these antipsychotic drugs in terms of cognition may be attributable to dose, duration of treatment and type of cognitive domain. Further research will add to the worldwide endeavor to develop more effective psychotropic drugs accompanied with minimal side effects, for the improvement of cognition, adherence and long-term outcome in patients with schizophrenia or other major psychiatric illnesses.

Attenuation of acute d-amphetamine-induced disruption of conflict resolution by clozapine, but not α-flupenthixol in rats

Previous research demonstrates that disruption of forebrain dopamine systems impairs the use of high-order information to guide goal-directed performance, and that this deficit may be related to impaired use of task-setting cues in patients with schizophrenia. Such deficits can be interrogated through conflict resolution, which has been demonstrated to be sensitive to prefrontal integrity in rodents. We sought to examine the effects of acute systemic d-amphetamine administration on the contextual control of response conflict in rats, and whether deficits were reversed through pre-treatment with clozapine or the D₁/D₂ antagonist α-flupenthixol. Acute d-amphetamine (1.5 mg/kg) disrupted the utilisation of contextual cues; therefore rats were impaired during presentation of stimulus compounds that require conflict resolution. Evidence suggested that this effect was attenuated through pre-treatment with the atypical antipsychotic clozapine (5.0 mg/kg), but not the typical antipsychotic α-flupenthixol (0.25 mg/kg), at doses previously shown to attenuate d-amphetamine-induced cognitive deficits. These studies therefore demonstrate a potentially viable model of disrupted executive function such as that seen in schizophrenia.

Complex relationships of nicotinic receptor actions and cognitive functions

Nicotine has been shown in a variety of studies to improve cognitive function including learning, memory and attention. Nicotine both stimulates and desensitizes nicotinic receptors, thus acting both as an agonist and a net antagonist. The relative roles of these two actions for nicotine-induced cognitive improvement have not yet been fully determined. We and others have found that acute nicotinic antagonist treatment can improve learning and attention. Nicotine acts on a variety of nicotinic receptor subtypes. The relative role and interactions of neuronal nicotinic receptor subtypes for cognition also needs to be better characterized. Nicotine acts on nicotinic receptors in a wide variety of brain areas. The role of some of these areas such as the hippocampus has been relatively well studied but other areas like the thalamus, which has the densest nicotinic receptor concentration are still only partially characterized. In a series of studies we characterized nicotinic receptor actions, anatomic localization and circuit interactions, which are critical to nicotine effects on the cognitive functions of learning, memory and attention. The relative role of increases and decreases in nicotinic receptor activation by nicotine were determined in regionally specific studies of the hippocampus, the amygdala, the frontal cortex and the mediodorsal thalamic nucleus with local infusions of antagonists of nicotinic receptor subtypes (α7 and α4β2). The understanding of the functional neural bases of cognitive function is fundamental to the more effective development of nicotinic drugs for treating cognitive dysfunction.

Pimavanserin, a selective serotonin (5-HT)2A-inverse agonist, enhances the efficacy and safety of risperidone, 2mg/day, but does not enhance efficacy of haloperidol, 2mg/day: comparison with reference dose risperidone, 6mg/day

Most atypical antipsychotic drugs (APDs), e.g. risperidone (RIS), produce more extensive blockade of brain serotonin (5-HT)(2A) than dopamine (DA) D(2) receptors. This distinguishes them from typical APDs, e.g. haloperidol (HAL). Our objective was to test the hypothesis that augmentation of low doses of RIS or HAL (2mg/day) with pimavanserin (PIM), a selective 5-HT(2A) inverse agonist, to enhance 5-HT(2A) receptor blockade, can achieve efficacy comparable to RIS, 6mg/day, but with lesser side effects. In a multi-center, randomized, double-blind, 6week trial, 423 patients with chronic schizophrenia experiencing a recent exacerbation of psychotic symptoms were randomized to RIS2mg+placebo (RIS2PBO), RIS2mg+PIM20mg (RIS2PIM), RIS6mg+PBO (RIS6PBO), HAL2mg+PBO (HAL2PBO), or HAL2mg+PIM20mg (HAL2PIM). Improvement in psychopathology was measured by the PANSS and CGI-S. The reduction in PANSS Total Score with RIS2PIM at endpoint was significantly greater than RIS2PBO: -23.0 vs. -16.3 (p=0.007), and not significantly different from the RIS6PBO group: -23.2 points. The percentage of patients with ≥20% improvement at day 15 in the RIS2PIM group was 62.3%, significantly greater than the RIS6PBO (42.1%; p=0.01) and the RIS2PBO groups (37.7%; p=0.002). Weight gain and hyperprolactinemia were greater in the RIS6PBO group than the RIS2PIM group but there was no difference in extrapyramidal side effects (EPS). HAL2PBO and HAL2PIM were not significantly different from each other in efficacy but HAL2PIM had less EPS at end point. Both HAL groups and RIS6PBO showed equal improvement in psychopathology at endpoint, indicating HAL 2mg/day is effective to treat an acute exacerbation in chronic schizophrenia patients. In conclusion, a sub-effective RIS dose combined with PIM to enhance 5-HT(2A) receptor blockade provided faster onset of action, and at endpoint, equal efficacy and better safety, compared to standard dose RIS. These results support the conclusion that 5-HT(2A) receptor blockade is a key component of the action of some atypical APDs and can reduce EPS due to a typical APD.

A systematic review of the evidence of clozapine's anti-aggressive effects

Reducing the risk of violent and aggressive behaviour in patients with schizophrenia remains a clinical priority. There is emerging evidence to suggest that the second-generation antipsychotic, clozapine, is effective at reducing this risk in patients with schizophrenia and some evidence to suggest that it may be best in selected patients. We conducted a systematic literature search in March 2011 of all prospective and retrospective studies, which investigated clozapine's anti-aggressive effects in a variety of mental disorders. The review identified six animal studies, four randomized controlled trials, 12 prospective non-controlled studies and 22 retrospective studies, with four case studies. We found considerable evidence in support of clozapine's ability to reduce violent and aggressive behaviour. Clozapine's anti-aggressive effect was most commonly explored in patients with schizophrenia, with less evidence available for other psychiatric disorders, including borderline personality disorder, autistic spectrum disorders, post-traumatic stress disorder, bipolar disorder and learning disability. There was mixed evidence to address the question of whether or not clozapine was any more effective than other antipsychotics. In the case of schizophrenia, there was evidence to suggest that clozapine's anti-aggressive effect was more marked particularly in those with treatment-resistant illness. Its anti-aggressive effects appeared to be 'specific', being to some extent greater than both its more general antipsychotic and sedative effects. There were significant methodological inconsistencies in the studies we identified, particularly surrounding patient recruitment criteria, the definition and measurement of violence and the lack of randomized, controlled trials. Data on therapeutic monitoring were also limited. Clozapine can reduce violence and persistent aggression in patients with schizophrenia and other psychiatric disorders. It may offer an advantage over other antipsychotics, although perhaps exclusively in the case of traditionally defined 'treatment resistance' or more broadly defined 'complex cases' with co-morbidity. Larger, randomized, blinded, controlled studies with robust characterization of participants, and standardized measures of violence and aggression are, however, needed to fully understand this link and explore the possible mechanisms.

Effects of sertindole on cognition in clozapine-treated schizophrenia patients

OBJECTIVE

To assess the cognitive effects of sertindole augmentation in clozapine-treated patients diagnosed with schizophrenia. Cognition is secondary outcome of the trial.

METHOD

A 12-week, double-blinded, randomized, placebo-controlled, augmentation study of patients treated with clozapine. Participants were randomized 1:1 to receive 16 mg of sertindole or placebo as adjunctive treatment to clozapine.

RESULTS

Participants displayed substantial cognitive deficits, ranging from 1.6 standard deviation below norms at baseline to more than three standard deviations on tests of response readiness and focused attention. There were no significant differences between sertindole augmentation and placebo groups at study end. Correlation analysis of Positive and Negative Syndrome (PANSS) subscales, Global Assessment of Functioning subscale (GAF-F) and Clinical Global Impression (CGI) with 20 neurocognitive indices was conducted, but no significant correlations were found. Second, we tested change from baseline to endpoint for the PANSS, GAF-F, and CGI, vs. the concomitant changes in cognitive test performance, and found no significant correlations.

CONCLUSION

The clozapine-treated patients displayed marked cognitive deficits at baseline. Adding sertindole did not improve or worsen cognitive functioning, which is in line with previous negative studies of the effect on cognition of augmenting clozapine treatment with another antipsychotic drug.

[Schizophrenia, psychotropic drugs and cognition]

The robust and specific associations between cognitive abilities and the functional prognosis of patients suffering from schizophrenia lead to a major concern for cognitive impairment in this disorder. Among the strategies considered to correct or enhance cognition in schizophrenia, drugs hold a pivotal place. Evidently, antipsychotic drugs, which are inextricable from patients' management, have generated considerable scrutiny in this topic. This paper first aims to outline the current views on the impact of antipsychotic drugs in schizophrenia. The distinction between conventional and atypical drugs is reminded in order to more precisely review existing data comparing the impact of these two types of molecules on cognitive impairment. More specifically, an elementary framework is proposed to facilitate the recognition of methodological flaws and offer a critical examination of previous findings. It emerges subsequently that differences between atypical and conventional drugs appear far less contrasted than initially suggested. Also, atypical antipsychotics compose a disparate pharmacological class and much clarification could be obtained by differentiating the individual effects of these molecules rather than considering them as a group. Finally, the relevance of these cognitive measures is also considered. In particular, we address alternative measures closer to real life situations as well as the growing interest in the broad field of social cognition. A last part of this article deals with strategies relying on adjunctive therapies. The fairly modest results obtained with these approaches is evoked and briefly reviewed.

Vulnerability in early life to changes in the rearing environment plays a crucial role in the aetiopathology of psychiatric disorders

Adverse events early in life, including maternal separation and social isolation, profoundly affect brain development and adult behaviour and may contribute to the occurrence of psychiatric disorders such as schizophrenia and mood disorders in genetically predisposed individuals. The molecular mechanisms underlying these environmentally induced developmental adaptations are unclear and best evaluated in animal paradigms with translational salience. In this study, we examined the effects in mice of maternal separation and/or social isolation for 6 h/d between postnatal days 15 and 21 on performance during adulthood in the open-field, social interaction, elevated plus-maze, forced swimming, Y-maze, novel object recognition, conditioned fear-learning, prepulse inhibition, and locomotor activity tests, to investigate whether this animal model could show the phenotypes for schizophrenia and mood disorders. The stress of maternal separation and isolation led to adult behavioural deficits, activation of the hypothalamic-pituitary-adrenal axis, and decreases in the levels of norepinephrine and dopamine in the frontal cortex and metabolites of dopamine and serotonin in the amygdala, showing the involvement of endocrine and neuronal risk in behavioural deficits. The results suggest that the frontal cortex and amygdala undergo structural remodelling induced by the stress of maternal separation and isolation, which alters behavioural and physiological responses in adulthood, including anxiety, memory and other cognitive processes. Further, social isolation enhanced the behavioural dysfunctions induced by maternal separation. These findings indicate that maternal separation and social isolation early in life can lead to long-lasting abnormal behaviour and pathophysiological impairments including schizophrenia and mood disorders.

Clozapine and global cognition in schizophrenia

OBJECTIVE

Clozapine (CLZ) has been shown to have a beneficial effect on cognition in schizophrenia in some studies and a detrimental effect in others. The relative effect and exposure to CLZ and its major metabolite-N-desmethylclozapine (NDMC)-could explain these discrepancies.

METHODS

Using a validated measure of global cognition, we performed 2 binary logistic regression models to assess the relationship among cognition, age, sex, CLZ dose, CLZ and NDMC plasma levels, and their ratio (CLZ/NDMC) in individuals with schizophrenia spectrum disorders. Model 1 included age, sex, CLZ dose, and CLZ and NDMC levels. Model 2 included age, sex, CLZ dose, and CLZ/NDMC.

RESULTS

Among 73 subjects (mean [SD] age, 41.6 [12.0] years), 16 (21.9%) had high cognitive impairment, whereas the rest had low cognitive. In model 1, age and CLZ level were associated with high cognitive impairment (odds ratio [95% confidence interval] for age, 1.079 [1.011-1.152]; CLZ level, 1.010 [1.003-1.017]), whereas NDMC level was associated with its absence (NDMC level, 0.987 [0.977-0.997]). In model 2, age, male sex, and CLZ/NDMC were associated with cognitive impairment (age, 1.083 [1.015-1.154]; sex, 0.178 [0.032-0.994]; CLZ/NDMC, 7.302 [1.823-29.253]). Clozapine dose was not associated with cognition in either model.

CONCLUSIONS

After controlling for age, sex, and dose, CLZ/NDMC was more strongly associated with cognition than CLZ or NDMC levels. N-desmethylclozapine agonist activity versus CLZ antagonist activity at the muscarinic receptors could explain the strength of the association of CLZ/NDMC with cognition.

Determinants of work outcome in neuroleptic-resistant schizophrenia and schizoaffective disorder: cognitive impairment and clozapine treatment

There is considerable evidence that cognitive impairment is a better predictor of work and social function in schizophrenia than are positive and negative symptoms. Atypical antipsychotic drugs have been shown to improve cognitive function in schizophrenia patients, but it is unclear whether this improves patients' ability to gain employment. Data from a prospective longitudinal study was used to test the hypotheses that (1) clozapine treatment would improve employment outcome in treatment-resistant schizophrenia or schizoaffective disorder patients, and (2) specific cognitive functioning at baseline and after treatment would predict work status at baseline and change in work status. Employment status and cognitive assessment data were collected in 59 treatment-resistant schizophrenia or schizoaffective disorder patients. Forty-seven of 59 (79.7%) patients were unemployed at baseline. Over a 12-month period, 23 (48.9%) additional patients were able to gain paid or volunteer jobs, or attend school. As predicted, neurocognitive performance was a better predictor of employment status and ability to gain of employment than clinical symptoms. Improvement in verbal working memory was found to be a better predictor of employment outcome than other cognitive functions. Treatment that enhances cognitive function, especially verbal working memory, may lead to better employment outcomes in treatment-resistant schizophrenia or schizoaffective disorder patients.

A randomized trial comparing clozapine and typical neuroleptic drugs in non-treatment-resistant schizophrenia

Clozapine has been shown to be superior to typical neuroleptic drugs for treating positive symptoms in treatment-resistant (TR) schizophrenia. Long-term data from randomized clinical trials comparing clozapine with typical neuroleptics in non-TR schizophrenia are rare. We previously reported that clozapine was superior to typical neuroleptic drugs in some domains of cognition in recent onset non-TR schizophrenia. We now present data on psychopathology and quality of life from this randomized, flexibly dosed, 24-month study of clozapine vs. typical neuroleptics in non-TR schizophrenia patients. Both treatments produced significant improvement in measures of psychopathology, quality of life, and global function, with minor exceptions. There was no difference in extrapyramidal side effects between the patients treated with clozapine or typical neuroleptics. However, significantly more relapse/rehospitalization drop-outs occurred in the typical neuroleptic group. Two patients treated with typical neuroleptics, but none treated with clozapine, became non-responsive to treatment. Clozapine was associated with significantly greater weight gain. Clozapine and typical neuroleptic drugs appear to produce equivalent improvement in psychopathology in patients with non-TR schizophrenia. Clozapine may be more effective than typical neuroleptics for treatment retention and prevention of relapse, but it produces more severe metabolic side effects. These considerations should be taken into account in decisions of how best to utilize clozapine in the treatment of schizophrenia.

Cognitive profiles of healthy siblings of schizophrenia patients: application of the cognitive domains of the MATRICS consensus battery

Even though a large body of data suggests the presence of various types of cognitive deficits in the unaffected relatives of schizophrenia patients, more study is needed to clarify the comparative sensitivities of specific cognitive measures for relative-control differences. In this study, the authors compared the cognitive profiles of unaffected siblings of schizophrenia patients and those of patients and normal controls, and attempted to identify cognitive markers that might be associated with genetic liability to schizophrenia. Eighty-eight clinically stable schizophrenia patients, 44 healthy patient siblings, and 100 normal controls were evaluated using comprehensive neuropsychological tests. The domain structure of the MATRICS consensus cognitive battery was adopted, and both domain scores and individual test scores were used in the analysis. Performances of the sibling group were intermediate between those of patients and controls on most measures. A significant difference between the sibling and control groups was observed only in the Category Fluency Test. This cognitive deficit might be caused by familial predisposition to schizophrenia and could be a candidate of endophenotype for schizophrenia.

Chronic clozapine treatment improves prenatal infection-induced working memory deficits without influencing adult hippocampal neurogenesis

BACKGROUND

Converging evidence indicates that prenatal exposure to immune challenge can induce long-term cognitive deficits relevant to schizophrenia. Such cognitive impairments may be related to deficient hippocampal neurogenesis at adult age.

OBJECTIVES

In the present study, we sought evidence for the possibility that chronic treatment with the reference atypical antipsychotic drug clozapine may improve prenatal infection-induced cognitive dysfunctions by stimulating adult hippocampal neurogenesis.

METHODS

This hypothesis was tested in a well-established mouse model of prenatal immune challenge which is based on prenatal administration of the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyI:C).

RESULTS

We found that maternal PolyI:C (5 mg/kg, i.v.) exposure on gestation day 17 led to significant spatial working memory impairment and reduced hippocampal neurogenesis in the resulting offspring at adult age. The latter effect was apparent in postmortem immunohistochemical analyses of the cell proliferation marker bromodeoxyuridine and the microtubule-associated protein doublecortin, a marker of newborn neuronal cells. Chronic (3 weeks) administration of clozapine (5 mg/kg/day, i.p.) significantly improved the prenatal PolyI:C-induced working memory deficits, while at the same time, it negatively affected working memory performance in adult offspring born to control mothers. These bidirectional cognitive effects of clozapine were not paralleled by concomitant effects on adult hippocampal neurogenesis.

CONCLUSIONS

Our findings do not support the hypothesis that the atypical antipsychotic drug clozapine may influence cognitive functions by acting on adult neurogenesis in the hippocampus, regardless of whether the drug is administered to subjects with or without a neurodevelopmental predisposition to adult neuropathology.

Clozapine versus typical neuroleptic medication for schizophrenia

BACKGROUND

Long-term drug treatment of schizophrenia with typical antipsychotics has limitations: 25 to 33% of patients have illnesses that are treatment-resistant. Clozapine is an antipsychotic drug, which is claimed to have superior efficacy and to cause fewer motor adverse effects than typical drugs for people with treatment-resistant illnesses. Clozapine carries a significant risk of serious blood disorders, which necessitates mandatory weekly blood monitoring at least during the first months of treatment.

OBJECTIVES

To evaluate the effects of clozapine compared with typical antipsychotic drugs in people with schizophrenia.

SEARCH STRATEGY

For the current update of this review (March 2006) we searched the Cochrane Schizophrenia Group Trials Register.

SELECTION CRITERIA

All relevant randomised clinical trials (RCTs).

DATA COLLECTION AND ANALYSIS

We extracted data independently. For dichotomous data we calculated relative risks (RR) and their 95% confidence intervals (CI) on an intention-to-treat basis, based on a fixed-effect model. We calculated numbers needed to treat/harm (NNT/NNH) where appropriate. For continuous data, we calculated weighted mean differences (WMD) again based on a fixed-effect model.

MAIN RESULTS

We have included 42 trials (3950 participants) in this review. Twenty-eight of the included studies are less than 13 weeks in duration, and, overall, trials were at significant risk of bias. We found no significant difference in the effects of clozapine and typical neuroleptic drugs for broad outcomes such as mortality, ability to work or suitability for discharge at the end of the study. Clinical improvements were seen more frequently in those taking clozapine (n=1119, 14 RCTs, RR 0.72 CI 0.7 to 0.8, NNT 6 CI 5 to 8). Also, participants given clozapine had fewer relapses than those on typical antipsychotic drugs (n=1303, RR 0.62 CI 0.5 to 0.8, NNT 21 CI 15 to 49). BPRS scores showed a greater reduction of symptoms in clozapine-treated patients, (n=1145, 16 RCTs, WMD -4.22 CI -5.4 to -3.1), although the data were heterogeneous (Chi(2) 0.0001, I(2) 66%). Short-term data from the SANS negative symptom scores favoured clozapine (n=196, 5 RCTs, WMD -5.92 CI -7.8 to -4.1). We found clozapine to be more acceptable in long-term treatment than conventional antipsychotic drugs (n=982, 16 RCTs, RR 0.60 CI 0.5 to 0.7, NNT 15 CI 12 to 20). Blood problems occurred more frequently in participants receiving clozapine (3.2%) compared with those given typical antipsychotics (0%) (n=1031, 13 RCTs, RR 7.09 CI 2.0 to 25.6). Clozapine participants experienced more drowsiness, hypersalivation, or temperature increase, than those given conventional neuroleptics. However, clozapine patients experienced fewer motor adverse effects (n=1433, 18 RCTs, RR 0.58 CI 0.5 to 0.7, NNT 5 CI 4 to 6).The clinical effects of clozapine were more pronounced in participants resistant to typical neuroleptics in terms of clinical improvement (n=370, 4 RCTs, RR 0.71 CI 0.6 to 0.8, NNT 4 CI 3 to 6) and symptom reduction. Thirty-four per cent of treatment-resistant participants had a clinical improvement with clozapine treatment.

AUTHORS' CONCLUSIONS

Clozapine may be more effective in reducing symptoms of schizophrenia, producing clinically meaningful improvements and postponing relapse, than typical antipsychotic drugs - but data are weak and prone to bias. Participants were more satisfied with clozapine treatment than with typical neuroleptic treatment. The clinical effect of clozapine, however, is, at least in the short term, not reflected in measures of global functioning such as ability to leave the hospital and maintain an occupation. The short-term benefits of clozapine have to be weighed against the risk of adverse effects. Within the context of trials, the potentially dangerous white blood cell decline seems to be more frequent in children and adolescents and in the elderly than in young adults or people of middle-age.The existing trials have largely neglected to assess the views of participants and their families on clozapine. More community-based long-term randomised trials are needed to evaluate the efficacy of clozapine on global and social functioning as trials in special groups such as people with learning disabilities.

GABAB receptor agonist baclofen improves methamphetamine-induced cognitive deficit in mice

In this study, we investigated the effects of GABA(A) and GABA(B) receptor agonists on the methamphetamine-induced impairment of recognition memory in mice. Repeated treatment with methamphetamine at a dose of 1 mg/kg for 7 days induced an impairment of recognition memory. Baclofen, a GABA(B) receptor agonist, ameliorated the repeated methamphetamine-induced cognitive impairment, although gaboxadol, a GABA(A) receptor agonist, had no significant effect. GABA(B) receptors may constitute a putative new target in treating cognitive deficits in patients suffering from schizophrenia, as well as methamphetamine psychosis.

Improvement by minocycline of methamphetamine-induced impairment of recognition memory in mice

INTRODUCTION

Cognitive deficits are a core feature of patients with schizophrenia and methamphetamine (METH) psychosis. We have recently found that repeated METH treatment (1 mg/kg, s.c.) in mice, which induces behavioral sensitization, impairs long-term recognition memory in a novel object recognition test (NORT) and that the impairment is ameliorated by clozapine, but not haloperidol. Recent studies indicate that minocycline, a second-generation tetracycline, has potent neuroprotective effects in various animal models of neurological diseases.

OBJECTIVES

In the present study, we investigated the effect of minocycline on learning and memory in the NORT and behavioral sensitization in mice that had been administered METH for 7 days.

RESULTS

When minocycline (20-40 mg/kg) was administered intraperitoneally once a day for seven consecutive days to mice that had previously been treated with METH for 7 days, it ameliorated the METH-induced impairment of recognition memory in a dose-dependent manner, although the same treatment with minocycline had no effect on behavioral sensitization to METH. The administration of minocycline, together with METH, inhibited the development of METH-induced behavioral sensitization. The improvement in memory caused by minocycline was associated with an amelioration of the novelty-induced activation of extracellular signal-regulated kinase 1/2 in the prefrontal cortex of METH-treated mice.

CONCLUSIONS

These results suggest that minocycline is useful for the treatment of cognitive deficits in patients with METH psychosis or schizophrenia.

Long-term effects of risperidone versus haloperidol on verbal memory, attention, and symptomatology in schizophrenia

There is evidence in the literature that cognitive functions in schizophrenia (SC) may be improved by atypical neuroleptics (NLPs) in contrast to typical medication, but there is still controversy regarding this apparent superiority of atypical drugs. In this study, we assessed the differential effects of risperidone and haloperidol on verbal memory, attention, and psychiatric symptoms in SC. The performance of 28 SC participants, randomly assigned to risperidone (2-6 mg/day) or haloperidol (2-40 mg/day), was compared with that of healthy controls. The California Verbal Learning Test (CVLT), the d2 Cancellation Test, and the Positive and Negative Symptoms Scale were administered at baseline and 3, 6, and 12 months. Relative to controls, all SC participants showed markedly impaired verbal memory and processing speed at each assessment period. There was no differential effect between the two NLPs on CVLT and d2 performance. However, risperidone was more effective than haloperidol in reducing psychiatric symptoms. Improvement in symptom severity was not associated with improvement in neurocognitive performance on these specific tests. Neither conventional nor atypical neuroleptic medications improved neurocognitive functioning over a 12-month follow-up, suggesting that psychopathological improvement under risperidone is independent of cognitive function.

Effect of olanzapine or risperidone treatment on some cognitive functions in a one-year follow-up of schizophrenia outpatients with prominent negative symptoms

AIMS

To compare olanzapine and risperidone outcome on some neurocognitive dimensions in chronic schizophrenia patients with prominent negative symptoms.

METHOD

We randomised and followed for 1 year 235 chronic schizophrenia outpatients with a SANS global score > or =10 to open-label flexible-dose treatment with olanzapine or risperidone. Clinical, functional and cognitive assessments [including the COGLAB battery reaction time, vigilance-span of apprehension (VSA) and a card-sorting task] were done periodically.

RESULTS

There were no significant differences between olanzapine (n=120) and risperidone (n=115) treatments in the neurocognitive dimensions tested. Mean+/-SD doses were 12.2+/-5.8 mg/day of olanzapine and 4.9+/-2.0 mg/day of risperidone. Patients in the olanzapine group showed a significant improvement in the VSA total score, but the within-group change was modest (effect size of 0.26); the difference with the risperidone group was not significant (p=0.207). Patients in both groups showed a significant improvement in a composite measure of executive efficiency based on the card-sorting task, with within-group effect size of 0.21 (risperidone) and 0.35 (olanzapine); the between-group difference was not significant (p=0.164). At baseline, better functional status correlated with VSA. Patients scoring lower on VSA or executive efficiency at baseline improved more on these respective measures.

CONCLUSION

Modest pro-cognitive effects can also be found in chronic schizophrenia outpatients with prominent negative symptoms when treated with olanzapine or risperidone.

Repeated methamphetamine treatment impairs spatial working memory in rats: reversal by clozapine but not haloperidol

RATIONALE

Although chronic use of methamphetamine (METH) leads to long-lasting cognitive dysfunction in humans, there are few reports about an animal model that reflects METH-induced impairment of working memory.

OBJECTIVES

In this study, we investigated the effect of repeated METH treatment on spatial working memory in rats.

MATERIALS AND METHODS

Rats were repeatedly administered METH (2 mg/kg) once a day for 7 days, and their memory function was assessed with a delayed spatial win-shift task in a radial arm maze. The task consisted of two phases, a training phase and a test phase, separated by a delay.

RESULTS

METH-treated animals showed an impairment of performance in the test phase when the delay time was increased from 5 to 30 min or longer. The effect of METH persisted for at least 14 days after the drug withdrawal. METH-induced impairment of working memory was reversed by clozapine (3 and 10 mg/kg, for 7 days), but not haloperidol (1 and 2 mg/kg, for 7 days). The improving effect of clozapine diminished 7 days after the withdrawal. Phosphorylated extracellular signal-regulated kinase1/2 (ERK1/2) levels were significantly increased in the hippocampus of saline-treated control rats from 5 to 60 min after the training phase. In contrast, hyperphosphorylation of ERK1/2 was abolished in the hippocampus of rats treated with METH.

CONCLUSIONS

These findings suggest that repeated METH treatment induces impairment of working memory, which is associated with a dysfunctional ERK1/2 pathway in the hippocampus. Furthermore, clozapine may be effective for the treatment of METH-induced cognitive dysfunction.

Factors affecting outcome in schizophrenia and their relevance for psychopharmacological treatment

A major focus of current treatment research in schizophrenia is the determinants of long-term outcome, including functional outcome and general medical well being, rather than just specific domains of psychopathology such as positive and negative symptoms, mood symptoms, and cognitive impairment. This focus does not negate the importance of the latter issues but sees them as factors contributing to long-term outcome to variable extents. A long-term treatment focus facilitates a more clinically relevant assessment of benefits versus risks of available treatments. For instance, atypical antipsychotic drugs as a group have clear advantages for several important domains of efficacy that may influence long-term outcome, but are also more expensive over the long term. Use of some agents may also result in deleterious physical health consequences as well as large additional costs over the long term owing to metabolic adverse effects. The present paper focuses on several key issues in schizophrenia which are important determinants of long-term outcome in schizophrenia, or influence choice of antipsychotic drugs, or both, including: (i) duration of untreated psychosis; (ii) impact of relapse on long-term outcome; (iii) limited efficacy for specific domains of psychopathology of current treatments; (iv) mortality owing to suicide; and (v) mortality owing to other causes (e.g. cardiovascular disease).

Nicotinic interactions with antipsychotic drugs, models of schizophrenia and impacts on cognitive function

People with schizophrenia often have substantial cognitive impairments, which may be related to nicotinic receptor deficits, (alpha7 and alpha4beta2), documented in the brains of people with schizophrenia. The large majority of people with schizophrenia smoke cigarettes. Thus, nicotinic interactions with antipsychotic drugs are widespread. Complementary co-therapies of novel nicotinic ligands are being developed to add to antipsychotic therapy to treat the cognitive impairment of schizophrenia. Thus, it is critical to understand the interaction between nicotinic treatments and antipsychotic drugs. Nicotinic interactions with antipsychotic drugs, are complex since both nicotine and antipsychotics have complex actions. Nicotine stimulates and desensitizes nicotinic receptors of various subtypes and potentiates the release of different neurotransmitters. Antipsychotics also act on a verity of receptor systems. For example, clozapine acts as an antagonist at a variety of neurotransmitter receptors such as those for dopamine, serotonin, norepinepherine and histamine. In a series of studies, we have found that in normally functioning rats, moderate doses of clozapine impair working memory and that clozapine blocks nicotine-induced memory and attentional improvement. Clozapine and nicotine can attenuate each other's beneficial effects in reversing the memory impairment caused by the psychototmimetic drug dizocilpine. A key to the clozapine-induced attenuation of nicotine-induced cognitive improvement appears to be its 5HT(2) antagonist properties. The selective 5HT(2) antagonist ketanserin has a similar action of blocking nicotine-induced memory and attentional improvements. It is important to consider the interactions between nicotinic and antipsychotic drugs to develop the most efficacious treatment for cognitive improvement in people with schizophrenia.

Psychomotor slowing in schizophrenia

Psychomotor slowing (PS) is a cluster of symptoms that was already recognized in schizophrenia by its earliest investigators. Nevertheless, few studies have been dedicated to the clarification of the nature and the role of the phenomenon in this illness. Moreover, slowed psychomotor functioning is often not clearly delineated from reduced processing speed. The current, first review of all existing literature on the subject discusses the key findings. Firstly, PS is a clinically observable feature that is most frequently established by neuropsychological measures assessing speed of fine movements such as writing or tasks that require rapid fingertip manipulations or the maintenance of maximal speed over brief periods of time in manual activities. Moreover, the slowed performance on the various psychomotor measures has been demonstrated independent of medication and has also been found to be associated with negative symptoms and, to a lesser extent, with positive and depressive symptoms. Importantly, performance on the psychomotor tasks proved related to the patients' social, clinical, and functional outcomes. Several imaging studies showed slowed performance to coincide with dopaminergic striatal activity. Finally, conventional neuroleptics do not improve the patients' PS symptoms, in contrast to the atypical agents that do seem to produce modestly improving effects.

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

It has been reported that antipsychotics may improve cognitive function in the treatment of schizophrenia. The present study examined the effect of haloperidol and risperidone on cognitive performance in schizophrenic patients. 95 healthy subjects and 68 schizophrenic patients were recruited for comparison of cognitive function. As 20 of the 68 schizophrenic patients were drug-naive, they were randomly divided into two groups and double-blinded for treatment with either haloperidol or risperidone for an 8-week period. Each subject received Wisconsin Card Sorting Test (WCST) and Maze paradigms for cognitive function performance. For schizophrenic patients, the Positive and Negative Syndrome Scale (PANSS) was used for evaluation of clinical symptoms. Results demonstrated that in both WCST and Maze paradigms the 68 schizophrenic patients had worse cognitive performance compared with healthy subjects. Of the 20 drug-naive schizophrenic patients from the 68 in-patients, both haloperidol and risperidone improved the clinical symptoms. Maze tasks performance was improved progressively after haloperidol and risperidone treatment, although improvement was greatest with risperidone. Both haloperidol and risperidone had no evident effect on WCST performance. Our findings suggest that Maze paradigms may be an ideal tool for evaluation of pharmacological treatment effects on cognitive function in schizophrenic patients. Furthermore, risperidone may have more treatment benefits than haloperidol on cognitive performance in drug-naive schizophrenic patients.

Fine-tuning of awake prefrontal cortex neurons by clozapine: comparison with haloperidol and N-desmethylclozapine

BACKGROUND

Mechanisms underlying clozapine's better clinical efficacy in schizophrenia remain poorly understood. The prefrontal cortex (PFC) has been implicated as a primary site for the therapeutic effects of clozapine; however, evidence for how clozapine influences the activity of PFC neurons in behaviorally relevant contexts is lacking.

METHODS

Ensemble single unit recording in awake rats was used to measure the activity of PFC neurons in response to clozapine, its main metabolite N-desmethylclozapine (DMClz), and the typical antipsychotic drug haloperidol during baseline conditions and after treatment with the N-methyl-D-aspartate antagonist MK801. Behavioral stereotypy was scored during recording.

RESULTS

Clozapine and DMClz but not haloperidol had an activity-dependent influence on spontaneous firing rate of PFC cells: they increased the activity of neurons with low baseline firing rates and decreased the activity of neurons with higher firing rates. Clozapine and DMClz but not haloperidol also reversed the effect of MK801 on PFC neuronal firing. This reversal was strongly correlated with blockade of MK801-induced behavioral stereotypy.

CONCLUSIONS

These findings indicate that clozapine has the capacity to fine-tune spontaneous and disrupted activity of PFC neurons. This effect might contribute, in part, to the therapeutic efficacy of clozapine in schizophrenia.

A meta-analysis of cognitive change with haloperidol in clinical trials of atypical antipsychotics: dose effects and comparison to practice effects

Prospective, double-blind, randomized trials comparing atypical antipsychotic drugs (APDs) to typical APDs, such as haloperidol, indicate that atypical APDs provide a modest benefit to cognitive function in schizophrenia. However, the validity of this inference has been contested by suggestions that the cognitive improvements observed with atypical APDs reflect practice effects associated with repeated testing on the same neuropsychological instruments, or an avoidance of a deleterious effect of haloperidol on cognitive function that might be dose related. These alternate hypotheses were assessed by meta-analyses that 1) examined the relationship between cognitive change and dose of haloperidol within the control arms of prospective atypical vs. typical APD clinical trials; and 2) compared the magnitude of change observed within the haloperidol arms of these studies to estimated practice effects for several commonly used neuropsychological measures. The results indicate that overall cognitive performance improves while on haloperidol. Studies that used a low dose of haloperidol (<10 mg) did not yield larger effect sizes for overall cognitive function or specific neuropsychological measures than studies that used a high dose (>10 mg), although doses greater than 24 mg appear to have deleterious effects. For two of the six neuropsychological tests examined (digit symbol substitution and verbal fluency) the magnitude of change observed was significantly less than practice effects. The results indicate that although haloperidol may cause deleterious effects at very high doses, or in specific cognitive domains, these effects are not likely to explain the broader range of cognitive improvements observed with atypical APDs.

A novel azaindolizinone derivative ZSET1446 (spiro[imidazo[1,2-a]pyridine-3,2-indan]-2(3H)-one) improves methamphetamine-induced impairment of recognition memory in mice by activating extracellular signal-regulated kinase 1/2

The effect of ZSET1446 (spiro[imidazo[1,2-a]pyridine-3,2-indan]-2(3H)-one) on cognitive impairment in mice, previously treated with methamphetamine (METH) at a dose of 1 mg/kg for 7 days, was investigated. ZSET1446 showed a significant ameliorating effect on METH-induced impairment of recognition memory, although it had no effect on exploratory behavior. ZSET1446 (1 microg/kg) recovered the defect of the novelty-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the prefrontal cortex (PFC) of METH-treated mice. The compound increased phosphorylated ERK1/2 levels in the hippocampus but not PFC of naive mice without affecting the total ERK1/2 levels. The ameliorating effect of ZSET1446 on recognition memory in METH-treated mice was negated by pretreatment with a mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor, SL327 (alpha-[amino-(4-aminophenylthio)methylene]-2-(trifluoromethyl)phenylacetonitrile). Furthermore, the dopamine D1 receptor antagonist, SCH23390 [R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine], and N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 [5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate)], blocked the ameliorating effect of ZSET1446 on METH-induced memory impairment, whereas the D2 receptor antagonist, raclopride, had no effect. These results suggest that the ameliorative effect of ZSET1446 on METH-induced memory impairment is associated with indirect activation of ERK1/2 following stimulation with dopamine D1 and NMDA receptors of the PFC. ZSET1446 would be a potential candidate for further preclinical study aimed at the treatment of cognitive deficits in Alzheimer's disease and schizophrenia, as well as METH psychosis.

Nicotinic-antipsychotic drug interactions and cognitive function

In summary, neuronal nicotinic systems are important for a variety of aspects of cognitive function impacted by antipsychotic drugs. It has been demonstrated that antipsychotic drugs have memory and attentional impairing effects when given to unimpaired subjects. Nicotine can reduce some of these impairments, but antipsychotic drug administration can also attenuate nicotine effects. We have found that nicotinic agonists selective for alpha7 and alpha4beta2 receptor subtypes significantly improve learning and memory. Serotonergic actions of antipsychotic drugs may decrease efficacy of nicotinic co-treatments. When the antipsychotic drug clozapine and nicotine are administered to subjects with cognitive impairments caused by NMDA glutamate receptor blockade or hippocampal dysfunction they can significantly attenuate the attentional and memory impairments. Nicotine has been shown in our studies to reverse the memory impairment caused by acute clozapine-induced memory improvement. Acute risperidone and haloperidol has been shown to attenuate nicotine-induced memory improvement. We have determined the role of hippocampal alpha7 and alpha4beta2 nicotinic receptors in the neural basis of nicotinic antipsychotic interactions. Local acute and chronic hippocampal infusion of either nicotinic alpha7 or alpha4beta2 antagonists cause significant spatial working memory impairment. Chronic hippocampal nicotinic antagonist infusions have served as a model of persistent decreases in nicotinic receptor level seen in schizophrenia and Alzheimer's disease. Clozapine attenuated the memory deficit caused by chronic suppression of hippocampal alpha4beta2 receptors while the amnestic effects of clozapine were potentiated by chronic suppression of hippocampal alpha7 receptors. Nicotinic co-treatment may be a useful adjunct in the treatment of schizophrenia, to attenuate cognitive impairment of schizophrenia. Nicotine as well as selective nicotinic alpha7 and alpha4beta2 receptor agonists significantly improve working memory and attentional function. Nicotine treatment was found to be effective in attenuating the attentional and memory impairments caused by the psychototmimetic NMDA antagonist dizocilpine (MK-801), a model of the cognitive impairment of schizophrenia. Studies of the interactions of antipsychotic drugs with nicotinic agents provided quite useful information concerning possible co-treatment of people with schizophrenia with nicotinic therapy. Nicotine was found to significantly attenuate the memory impairments caused by the antipsychotic drugs clozapine and olanzapine. Interestingly, nicotine-induced cognitive improvement was significantly attenuated by the antipsychotic drug clozapine. One of the principal effects of clozapine is to block 5HT2 receptors. Ketanserin a 5HT2 antagonist significantly attenuated nicotine-induced improvements in attention and memory. Thus it appears that antipsychotic drugs with actions blocking 5HT2 receptors may limit the efficacy of nicotinic co-treatments for cognitive enhancement.

The impact of atypical antipsychotic medications on long-term memory dysfunction in schizophrenia spectrum disorder: a quantitative review

This meta-analytic review examines the efficacy of antipsychotic medications in ameliorating schizophrenia-related long-term memory (LTM) impairments. Twenty-three studies were reviewed that compared schizophrenia spectrum patients treated (a) with atypical versus typical antipsychotic medications, or (b) with various atypical treatments. In 17 atypical versus typical trials aggregating 939 participants, superior overall (verbal and nonverbal) LTM was detected in patients assigned to atypical trials. However, this difference was small (effect size estimate (ES) 0.17; 95% Confidence Interval (CI) 0.04 to 0.31) and specific to certain atypical treatments. Relative to typical antipsychotic trials, LTM superiority was marginally significant for risperidone trials (ES 0.20; 95% CI -0.03 to 0.44) and significant for olanzapine trials (ES 0.29; 95% CI 0.08 to 0.49). In contrast, clozapine trials did not produce a LTM advantage over typical trials (ES -0.06; 95% CI -0.35 to 0.23). Due to the lack of available studies, the effect of quetiapine was indeterminate. Direct comparison between atypical trials revealed a similar effect pattern. A marginally significant superiority in overall LTM was detected for risperidone and olanzapine compared to clozapine (ES 0.28; 95% CI -0.04 to 0.59), which reached significance for verbal LTM (ES 0.36; 95% CI 0.04 to 0.67). Finally, the beneficial impact of antipsychotic medications emerged as a function of differences in the anticholinergic properties of the treatment arms being compared.

Serum concentrations of clozapine and norclozapine in the prediction of relapse of patients with schizophrenia

Schizophrenic outpatients (n=102) whose condition had stabilized with clozapine (CLZ) therapy and were being maintained on CLZ were followed for 1 year. Clinical status and concentrations of serum clozapine (CLZ) and its metabolite norclozapine (NCLZ) were evaluated periodically or when relapse occurred. Relapse was defined as a significant exacerbation of psychotic symptoms or hospitalization. Thirty-three patients relapsed and 69 did not. Relapse patients displayed significantly lower serum concentrations of CLZ and a sum of CLZ and NCLZ at endpoint than non-relapses (CLZ: 162 ng/ml vs. 237 ng/ml, p<0.001; CLZ+NCLZ: 225 ng/ml vs. 301 ng/ml, p<0.001). When all subjects were pooled together, a significant inverse correlation was observed between percent increase in the total score on the Brief Psychiatric Rating Scale (BPRS) from baseline and serum levels of CLZ alone (r=0.404, p<0.001) and the sum of CLZ and NCLZ (r=0.364, p<0.001). Relapses and non-relapses were well separated by a threshold CLZ serum concentration of 200 ng/ml with a sensitivity of 73% and a specificity of 80%. The threshold value represented about a 40% lower serum CLZ level than concentration achieved in acute treatment. Survival analysis showed a similarity of the relapse risk over time defined by the CLZ serum threshold and by symptomatic criteria. These results suggest that effective relapse prevention may require maintenance of patients at CLZ serum concentrations above 200 ng/ml and above 60% of the acute-phase level during long-term maintenance treatment of schizophrenia.

Perospirone in the treatment of schizophrenia: effect on verbal memory organization

The present study was performed to determine if perospirone, a novel antipsychotic drug with D2/5-HT2A antagonist and partial 5-HT1A agonist properties, would improve memory organization in twelve patients with chronic schizophrenia. Switching to equivalent dose of perospirone from prior antipsychotic medication was associated with a significant improvement in indices of verbal memory organization of the Auditory Verbal Learning Test. Negative symptoms and extrapyramidal side effects were also ameliorated after switching to perospirone. The distinct cognitive enhancement profile of perospirone may be attributable to its partial 5-HT1A agonist action.

Repeated methamphetamine treatment impairs recognition memory through a failure of novelty-induced ERK1/2 activation in the prefrontal cortex of mice

BACKGROUND

Recent clinical studies have suggested that chronic use of methamphetamine (METH) induces long-term cognitive deficits. To clarify the mechanism of METH-induced cognitive impairment, we investigated the effect of METH on cognitive function in mice.

METHODS

Mice were repeatedly administered METH for 7 days, and their cognitive function was assessed using a novel-object recognition task. Therapeutic effects of clozapine and haloperidol on METH-induced cognitive impairment were investigated. Western blotting and specific inhibitors were employed to determine the role of extracellular signal-regulated kinase 1/2 (ERK1/2).

RESULTS

Repeated METH treatment induced an impairment of recognition of novel objects and behavioral sensitization. These effects persisted for at least 28 days after the drug withdrawal. Clozapine, but not haloperidol, reduced METH-induced cognitive impairment. Hyperphosphorylation of ERK1/2 was found in the prefrontal cortex of mice exposed to the novel objects, but was abolished in mice treated with METH. Inhibition of ERK1/2 by the microinjection of PD98059 into the prefrontal cortex resulted in cognitive impairment.

CONCLUSIONS

These results suggest that repeated METH treatment induces cognitive impairment, which is associated with the dysfunction of the ERK1/2 pathway in the prefrontal cortex.

The effects of clozapine on delayed spatial alternation deficits in rats with hippocampal damage

Clozapine is an atypical antipsychotic drug that has been shown to improve spatial memory in some animal models; however its efficacy in reversing spatial memory impairment in rats with hippocampal lesions is unknown. To address this issue, we tested the effects of clozapine on delayed spatial alternation deficits in rats with hippocampal damage in three separate experiments. In each experiment, adult male rats received sham surgery or direct stereotaxic infusions of the excitotoxin, NMDA, into the hippocampus. In the first study, seven days after surgery, the sham control animals received daily saline injections while the lesioned animals were split into two groups that received daily saline or clozapine (2.0 mg/kg, sc) injections. During the fifth week of injections, all animals were tested in a food-motivated delayed spatial alternation task. Saline-treated rats with excitotoxic hippocampal damage displayed significant deficits in delayed spatial alternation. Daily clozapine injections completely reversed this deficit. In a second experiment, it was found that clozapine treatment limited to the testing days only did not improve alternation performance in lesioned rats. Finally, in a third experiment, chronic clozapine treatment did not improve alternation performance in lesioned rats that were pre-trained in the alternation task prior to surgery. These results suggest that chronic, but not acute, clozapine treatment enables rats with hippocampal damage to develop new spatial learning, but can not rescue old spatial learning established prior to damage. These results may have implications for the treatment of cognitive deficits caused by hippocampal dysfunction in disorders such as schizophrenia, Alzheimer's disease, and others.

Reversal of clozapine effects on working memory in rats with fimbria-fornix lesions

Clozapine is an effective antipsychotic drug, but its effects on cognitive function are unclear. Previously, we found that clozapine caused a working memory deficit, which was reversed by nicotine. Hippocampal systems are important in determining clozapine effect on memory. In the current study, the memory effects of clozapine and nicotine administration were determined in rats with lesions of the fimbria-fornix, a fiber bundle which carries cholinergic and other projections between the septum and the hippocampus. Female Sprague-Dawley rats were trained on a win-shift procedure in the radial-arm maze, in which each arm entry was rewarded once per session. Then, 13 rats received bilateral knife-cut lesions of the fimbria-fornix, while 14 rats underwent sham surgery. The rats were tested after subcutaneous injections with combinations of clozapine (0 and 1.25 mg/kg) and nicotine (0, 0.2, and 0.4 mg/kg). In sham-operated rats, clozapine caused a significant (P<0.005) working memory impairment. Fimbria-fornix lesions also caused a significant (P<0.05) memory impairment. Interestingly, clozapine had the opposite effect on working memory in the lesioned vs sham-operated rats. In contrast to its effects in controls, clozapine (1.25 mg/kg) significantly (P<0.05) attenuated the working memory deficit caused by fimbria-fornix lesions. Nicotine (0.2 mg/kg) did not quite significantly improve memory in lesioned rats. The effects of clozapine and nicotine were not additive in the lesioned rats. This study demonstrates the efficacy of clozapine in improving working memory in fimbria-fornix-lesioned rats, whereas it causes impairments in intact rats. Therapeutic treatment with clozapine in people with malfunctions of the hippocampus such as seen in schizophrenia may improve cognitive performance, whereas the same doses of clozapine may impair memory in individuals without hippocampal malfunction.

The locus coeruleus in schizophrenia: a postmortem study of noradrenergic neurones

Despite evidence for an abnormality of noradrenergic function in schizophrenia, it remains unclear whether the number of noradrenergic neurones is normal in patients with the disorder. In postmortem, formalin-fixed tissue from 15 schizophrenic patients and 18 controls matched for age and gender, we made estimates of the number and size of tyrosine-hydroxylase-immunoreactive cells in the locus coeruleus (LC). No significant difference was detected between these groups in the cross-sectional area or diameter of immunoreactive cell profiles. Profile number was not significantly affected by gender, side of the brainstem (left or right), postmortem interval or time in formalin; however, the levels of immunoreaction product (optical density) correlated significantly with our profile counts, which were lower on average in the schizophrenic group. When optical density was included as a covariate in our comparison (a repeated-measures analysis of variance) of schizophrenic and control cases, we found no difference between these groups in the number of neurones counted. An age-related decrease in profile number was detected, but no effect of age on our estimates of cell size was apparent. Our results highlight the importance of accounting for potential confounding variables, including variations in the quality of immunostaining, in investigations of this type. The findings presented here concur with previous studies suggesting that noradrenergic dysfunction in schizophrenia is not associated with an anatomical abnormality at the level of the LC.

Prediction of changes in memory performance by plasma homovanillic acid levels in clozapine-treated patients with schizophrenia

RATIONALE

Cognitive dysfunction in schizophrenia has been demonstrated to be dependent, in part, on dopaminergic activity. Clozapine has been found to improve some domains of cognition, including verbal memory, in patients with schizophrenia.

OBJECTIVES

This study tested the hypothesis that plasma homovanillic acid (pHVA) levels, a peripheral measure of central dopaminergic activity, would predict the change in memory performance in patients with schizophrenia treated with clozapine.

METHODS

Twenty-seven male patients with schizophrenia received clozapine treatment for 6 weeks. Verbal list learning (VLL)-Delayed Recall (VLL-DR), a test of secondary verbal memory, was administered before and after clozapine treatment. Blood samples to measure pHVA levels were collected at baseline.

RESULTS

Baseline pHVA levels were negatively correlated with change in performance on VLL-DR; the lower baseline pHVA level was associated with greater improvement in performance on VLL-DR during treatment with clozapine. Baseline pHVA levels in subjects who showed improvement in verbal memory during clozapine treatment ( n=13) were significantly lower than those in subjects whose memory performance did not improve ( n=14).

CONCLUSIONS

The results of this study indicate that baseline pHVA levels predict the ability of clozapine to improve memory performance in patients with schizophrenia.

The role of M1 muscarinic receptor agonism of N-desmethylclozapine in the unique clinical effects of clozapine

RATIONALE

Clozapine is a unique antipsychotic, with efficacy against positive symptoms in treatment-resistant schizophrenic patients, and the ability to improve cognition and treat the negative symptoms characteristic of this disease. Despite its unique clinical actions, no specific molecular mechanism responsible for these actions has yet been described.

OBJECTIVES AND METHODS

To comprehensively profile a large library of neuropsychiatric drugs, including most antipsychotics, at human monoamine receptors using R-SAT, an in vitro functional assay.

RESULTS

Profiling revealed that N-desmethylclozapine (NDMC), the principal metabolite of clozapine, but not clozapine itself, is a potent and efficacious muscarinic receptor agonist, a molecular property not shared by any other antipsychotic. To further explore the role of NDMC muscarinic receptor agonist properties in mediating the physiological actions of clozapine, systemically administered NDMC was found to stimulate the phosphorylation of mitogen-activated protein kinase (MAP kinase) in mouse CA1 hippocampal neurons, an effect that was blocked by scopolamine, confirming central M1 muscarinic receptor agonist activity in vivo. Lastly, an analysis of clozapine and NDMC serum levels in schizophrenic patients indicated that high NDMC/clozapine ratios better predicted improvement in cognitive functioning and quality of life than the levels of either compound alone.

CONCLUSIONS

The muscarinic receptor agonist activities of NDMC are unique among antipsychotics, and provide a possible molecular basis for the superior clinical effects of clozapine pharmacotherapy.

Cognitive factors in schizophrenia: causes, impact, and treatment

Greater attention has been given to the cognitive dimension in schizophrenia in recent years. This has resulted from increased recognition that cognitive impairment and negative symptoms of the disease have a greater impact on quality of life (QOL) compared to positive symptoms. Successful treatment of positive symptoms in patients with schizophrenia has not been shown to robustly translate into improvements in employment status or social relationships, while cognitive improvements are strongly associated with these important aspects of QOL and independence. These findings are based on extensive testing with standard cognitive tests for measuring executive function, verbal learning and memory, word recall, verbal working memory, spatial working memory, attention, and vigilance. Verbal learning and executive function, in particular, have been found to be valid predictors of employment success independent of the degree of severity of positive symptoms.

A meta-analysis and critical review of the effects of conventional neuroleptic treatment on cognition in schizophrenia: opening a closed book

BACKGROUND

In recent years, numerous studies have examined whether new-generation antipsychotic agents impact cognitive impairment in patients with schizophrenia when compared with conventional antipsychotic treatment. The working assumption of such studies, supported by narrative reviews, is that the conventional antipsychotic medications have little or no effect on cognition. The studies concerning the effects of conventional neuroleptics on cognition, however, have never been analyzed quantitatively. In this meta-analysis, we revisit the question of whether typical agents might have enhancing effects on cognition.

METHODS

The meta-analysis included studies that 1) compared the effects of typical neuroleptic agents with those of placebo or no medication on cognition; 2) examined adult patients identified as having schizophrenia; and 3) produced adequate data to estimate an effect size. Studies were identified by searches of computerized literature databases and by cross-referencing included studies. The effect size calculated was d, the difference between the means in cognitive measures of patients with schizophrenia taking and not taking conventional neuroleptic medication, divided by the pooled SD. Critically, when multiple measures were reported in a single article, effect sizes were combined so as to minimize the possibility that one study had undue weight simply because of the number of cognitive outcome variables that it contained. These results were corrected for bias due to sample size, with each of the effect sizes weighted by the reciprocal of its variance. The final sample after exclusion of outliers comprised 208 effect sizes from 34 studies.

RESULTS

With a random-effects model, effect sizes from the primary studies were weighted according to sample size and averaged. The resulting mean effect size was.22 (95% confidence interval =.10,.34). The result is positive, in that the range did not include zero and was of low moderate size. No moderating effects of study design or patient qualities were found to be significant. With the same procedures, effect sizes for individual neurocognitive domains were computed. Effect sizes were generally in the.13-.29 range for the majority of cognitive functions, whereas motor function was impacted negatively (-.11). Unexpectedly, medication dose did not correlate with effect size.

CONCLUSIONS

Typical antipsychotic medication provides modest-to-moderate gains in multiple cognitive domains. Given unavoidable methodologic limitations of the primary studies, current findings suggest that the impact of conventional medication on cognitive function should be re-evaluated.