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Treatment-resistant schizophrenia affects approximately 30% of individuals with the disorder. Clozapine is the medication of choice in treatment-resistant schizophrenia, but optimizing administration and dose titration is complex. The identification of factors influencing clozapine prescription and response, including genetics, is of interest in a precision psychiatry framework. We used linear regression models accounting for demographic, pharmacological, and clinical covariates to determine whether a polygenic risk score (PRS) for schizophrenia would be associated with the highest dose recorded during clozapine treatment. Analyses were performed across 2 independent multiancestry samples of individuals from a UK patient monitoring system, CLOZUK2 (n = 3133) and CLOZUK3 (n = 909), and a European sample from a Norwegian therapeutic drug monitoring service (n = 417). In a secondary analysis merging both UK cohorts, logistic regression models were used to estimate the relationship between schizophrenia PRSs and clozapine doses classified as low, standard, or high. After controlling for relevant covariates, the schizophrenia PRS was correlated with the highest clozapine dose on record for each individual across all samples: CLOZUK2 (β = 12.22, SE = 3.78, p =.001), CLOZUK3 (β = 12.73, SE = 5.99, p =.034), and the Norwegian cohort (β = 46.45, SE = 18.83, p =.014). In a secondary analysis, the schizophrenia PRS was associated with taking clozapine doses >600 mg/day (odds ratio = 1.279, p =.006). The schizophrenia PRS was associated with the highest clozapine dose prescribed for an individual in records from 3 independent samples, suggesting that the genetic liability for schizophrenia might index factors associated with therapeutic decisions in cohorts of patients with treatment-resistant schizophrenia. [ABSTRACT FROM AUTHOR]

Schizophrenia (SZ) is associated with increased all-cause mortality, smoking, and age-associated proteins, yet multiple previous studies found no association between SZ and biological age using Horvath's epigenetic clock, a well-established aging biomarker based on DNA methylation. However, numerous epigenetic clocks that may capture distinct aspects of aging have been developed. This study tested the hypothesis that altered aging in SZ manifests in these other clocks. We performed a comprehensive analysis of 14 epigenetic clocks categorized according to what they were trained to predict: chronological age, mortality, mitotic divisions, or telomere length. To understand the etiology of biological age differences, we also examined DNA methylation predictors of smoking, alcohol, body mass index, serum proteins, and cell proportions. We independently analyzed 3 publicly available multiethnic DNA methylation data sets from whole blood, a total of 567 SZ cases and 594 nonpsychiatric controls. All data sets showed accelerations in SZ for the 3 mortality clocks up to 5 years, driven by smoking and elevated levels of 6 age-associated proteins. The 2 mitotic clocks were decelerated in SZ related to antitumor natural killer and CD8T cells, which may help explain conflicting reports about low cancer rates in epidemiological studies of SZ. One cohort with available medication data showed that clozapine is associated with male-specific decelerations up to 7 years in multiple chronological age clocks. Our study demonstrates the utility of studying the various epigenetic clocks in tandem and highlights potential mechanisms by which mental illness influences long-term outcomes, including cancer and early mortality. [ABSTRACT FROM AUTHOR]

Abstract Background In terms of antipsychotic treatment response, patients with schizophrenia can be classified into three groups: 1) treatment resistant to both non-clozapine (non-CLZ) antipsychotics and CLZ (ultra-treatment-resistant schizophrenia [URS]), 2) treatment resistant to non-CLZ antipsychotics but CLZ-responsive schizophrenia [non-URS]), and 3) responsive to first-line antipsychotics (non-treatment-resistant schizophrenia). This study aimed to compare glutamatergic neurometabolite levels among these three patient groups and healthy control subjects using proton magnetic resonance spectroscopy. Methods Glutamate and glutamate+glutamine levels were assessed in the caudate, the dorsal anterior cingulate cortex (dACC), and the dorsolateral prefrontal cortex using 3T proton magnetic resonance spectroscopy (point-resolved spectroscopy, echo time = 35 ms). Glutamatergic neurometabolite levels were compared between the groups. Results A total of 100 participants were included, consisting of 26 patients with URS, 27 patients with non-URS, 21 patients with non-treatment-resistant schizophrenia, and 26 healthy control subjects. Group differences were detected in ACC glutamate+glutamine levels (F 3,96 = 2.93, p =.038); patients with URS showed higher dACC glutamate+glutamine levels than healthy control subjects (p =.038). There were no group differences in the caudate or dorsolateral prefrontal cortex. Conclusions Taken together with previous studies that demonstrated higher ACC glutamate levels in patients with treatment-resistant schizophrenia, this study suggests that higher levels of ACC glutamatergic metabolites may be among the shared biological characteristics of treatment resistance to antipsychotics, including CLZ. [ABSTRACT FROM AUTHOR]

Background Clozapine is the last-line antipsychotic agent for refractory schizophrenia. To date, there is no convincing evidence for augmentation on clozapine. Activation of N -methyl-D-aspartate receptors, including inhibition of D-amino acid oxidase that may metabolize D-amino acids, has been reported to be beneficial for patients receiving antipsychotics other than clozapine. This study aimed to examine the efficacy and safety of a D-amino acid oxidase inhibitor, sodium benzoate, for schizophrenia patients who had poor response to clozapine. Methods We conducted a randomized, double-blind, placebo-controlled trial. Sixty schizophrenia inpatients that had been stabilized with clozapine were allocated into three groups for 6 weeks’ add-on treatment of 1 g/day sodium benzoate, 2 g/day sodium benzoate, or placebo. The primary outcome measures were Positive and Negative Syndrome Scale (PANSS) total score, Scale for the Assessment of Negative Symptoms, Quality of Life Scale, and Global Assessment of Functioning. Side effects and cognitive functions were also measured. Results Both doses of sodium benzoate produced better improvement than placebo in the Scale for the Assessment of Negative Symptoms. The 2 g/day sodium benzoate also produced better improvement than placebo in PANSS-total score, PANSS-positive score, and Quality of Life Scale. Sodium benzoate was well tolerated without evident side effects. The changes of catalase, an antioxidant, were different among the three groups and correlated with the improvement of PANSS-total score and PANSS-positive score in the sodium benzoate group. Conclusions Sodium benzoate adjuvant therapy improved symptomatology of patients with clozapine-resistant schizophrenia. Further studies are warranted to elucidate the optimal dose and treatment duration as well as the mechanisms of sodium benzoate for clozapine-resistant schizophrenia. [ABSTRACT FROM AUTHOR]

Background Clozapine-induced agranulocytosis (CIA)/clozapine-induced granulocytopenia (CIG) (CIAG) is a life-threatening event for schizophrenic subjects treated with clozapine. Methods To examine the genetic factor for CIAG, a genome-wide pharmacogenomic analysis was conducted using 50 subjects with CIAG and 2905 control subjects. Results We identified a significant association in the human leukocyte antigen (HLA) region (rs1800625, p = 3.46 × 10 −9 , odds ratio [OR] = 3.8); therefore, subsequent HLA typing was performed. We detected a significant association of HLA-B*59:01 with CIAG ( p = 3.81 × 10 −8 , OR = 10.7) and confirmed this association by comparing with an independent clozapine-tolerant control group ( n = 380, p = 2.97 × 10 −5 , OR = 6.3). As we observed that the OR of CIA (OR: 9.3~15.8) was approximately double that in CIG (OR: 4.4~7.4), we hypothesized that the CIG subjects were a mixed population of those who potentially would develop CIA and those who would not develop CIA (non-CIA). This hypothesis allowed the proportion of the CIG who were non-CIA to be calculated, enabling us to estimate the positive predictive value of the nonrisk allele on non-CIA in CIG subjects. Assuming this model, we estimated that 1) ~50% of CIG subjects would be non-CIA; and 2) ~60% of the CIG subjects without the risk allele would be non-CIA and therefore not expected to develop CIA. Conclusions Our results suggest that HLA-B*59:01 is a risk factor for CIAG in the Japanese population. Furthermore, if our model is true, the results suggest that rechallenging certain CIG subjects with clozapine may not be always contraindicated. [ABSTRACT FROM AUTHOR]

Background The neurobiological basis of action of noncompetitive N -methyl-D-aspartate acid receptor (NMDA-R) antagonists is poorly understood. Electrophysiological studies indicate that phencyclidine (PCP) markedly disrupts neuronal activity with an overall excitatory effect and reduces the power of low-frequency oscillations (LFO; <4 Hz) in thalamocortical networks. Because the reticular nucleus of the thalamus (RtN) provides tonic feed-forward inhibition to the rest of the thalamic nuclei, we examined the effect of PCP on RtN activity, under the working hypothesis that NMDA-R blockade in RtN would disinhibit thalamocortical networks. Methods Drug effects (PCP followed by clozapine) on the activity of RtN (single unit and local field potential recordings) and prefrontal cortex (PFC; electrocorticogram) in anesthetized rats were assessed. Results PCP (.25–.5 mg/kg, intravenous) reduced the discharge rate of 19 of 21 RtN neurons to 37% of baseline ( p < .000001) and the power of LFO in RtN and PFC to ~20% of baseline ( p < .001). PCP also reduced the coherence between PFC and RtN in the LFO range. A low clozapine dose (1 mg/kg intravenous) significantly countered the effect of PCP on LFO in PFC but not in RtN and further reduced the discharge rate of RtN neurons. However, clozapine administration partly antagonized the fall in coherence and phase-locking values produced by PCP. Conclusions PCP activates thalamocortical circuits in a bottom - up manner by reducing the activity of RtN neurons, which tonically inhibit thalamic relay neurons. However, clozapine reversal of PCP effects is not driven by restoring RtN activity and may involve a cortical action. [ABSTRACT FROM AUTHOR]

Background: Noncompetitive N-methyl-D-aspartate receptor antagonists are widely used as pharmacological models of schizophrenia. Their neurobiological actions are still poorly understood, although the prefrontal cortex (PFC) appears as a key target area. Methods: We examined the effect of phencyclidine (PCP) on neuronal activity of the mediodorsal (MD) and centromedial (CM) thalamic nuclei, reciprocally connected with the PFC, using extracellular recordings (n = 50 neurons from 35 Wistar rats) and c-fos expression. Results: Phencyclidine (.25 mg/kg intravenous [IV]) markedly disorganized the activity of MD/CM neurons, increasing (424%) and decreasing (41%) the activity of 57% and 20% of the recorded neurons, respectively (23% remained unaffected). Phencyclidine reduced delta oscillations (.15–4 Hz) as assessed by recording local field potentials. The subsequent clozapine administration (1 mg/kg IV) reversed PCP effects on neuronal discharge and delta oscillations. Double in situ hybridization experiments revealed that PCP (10 mg/kg intraperitoneal [IP]) markedly increased c-fos expression in glutamatergic neurons of several cortical areas (prefrontal, somatosensory, retrosplenial, entorhinal) and in thalamic nuclei, including MD/CM. Phencyclidine also increased c-fos expression in the amygdala; yet, it had a small effect in the hippocampus. Phencyclidine did not increase c-fos expression in gamma-aminobutyric acidergic cells except in hippocampus, amygdala, somatosensory, and retrosplenial cortices. Clozapine (5 mg/kg IP) had no effect by itself but significantly prevented PCP-induced c-fos expression. Conclusions: Phencyclidine likely exerts its psychotomimetic action by increasing excitatory neurotransmission in thalamo-cortico-thalamic networks involving, among others, PFC, retrosplenial, and somatosensory cortices. The antipsychotic action of clozapine includes, among other actions, an attenuation of the neuronal hyperactivity in thalamocortical networks. [Copyright &y& Elsevier]

Background: Schizophrenia is a neuropsychiatric disorder of a neurodevelopmental origin manifested symptomatically after puberty. Structural neuroimaging studies show that neuroanatomical aberrations occur before onset of symptoms, raising a question of whether schizophrenia can be prevented. Treatment with atypical antipsychotic drugs before the development of the full clinical phenotype might reduce the risk of transition to psychosis, but it remains unknown whether neuroanatomical abnormalities can be prevented. We used a neurodevelopmental animal model of schizophrenia to assess the efficacy of the atypical antipsychotic clozapine to prevent neuroanatomical deterioration. Methods: Pregnant rats received injection on gestational day 15 with the viral mimic polyriboinosinic-polyribocytidylic acid (PolyI:C) or saline. Structural brain changes in the male offspring were assessed at adolescence and adulthood (35 days and 120 days) with structural neuroimaging. In the second part, male offspring of PolyI:C- and saline-treated dams received daily clozapine (7.5 mg/kg) or saline injection in adolescence (days 34–47) and underwent behavioral testing and imaging at adulthood (from 90 days onward). Results: In utero exposure to maternal infection led in the offspring to postpubertal emergence of hallmark structural abnormalities associated with schizophrenia, enlarged ventricles, and smaller hippocampus. These abnormalities were not observed in the offspring of mothers who received PolyI:C that were treated with clozapine in adolescence. This was paralleled by prevention of behavioral abnormalities phenotypic of schizophrenia, attentional deficit, and hypersensitivity to amphetamine. Conclusions: This is the first demonstration that pharmacological intervention during adolescence can prevent the emergence of brain structural changes resulting from in-utero insult. [Copyright &y& Elsevier]

Background: Cortical inhibition (CI) deficits assessed by transcranial magnetic stimulation paradigms, short-interval cortical inhibition (SICI), and cortical silent period (CSP) have been demonstrated in schizophrenia (SCZ) patients. Antipsychotic treatments can modify CI and improve clinical symptoms, suggesting a neurophysiological link between the two. Previous studies have demonstrated that clozapine is associated with prolongation in CSP, a γ-hydroxybutyric acid (GABA)B-mediated phenomenon. Furthermore, SICI deficits were associated with psychotic symptom severity, suggesting alternation in GABAA-mediated neurotransmission. Such differential association patterns between clinical symptoms and CI deficits and their relationship to antipsychotic treatment thus might provide insights to the pathophysiology of schizophrenia. Methods: CI was assessed in 78 SCZ patients and 38 healthy subjects. Clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS). Subjects were grouped according to antipsychotic medication status: unmedicated (n = 7), clozapine (n = 19), olanzapine/quetiapine (n = 32), and risperidone/typical antipsychotics (n = 20). Results: Relative to control subjects, patients receiving clozapine had longer CSP and reduced SICI, whereas patients receiving other antipsychotics and unmedicated patients had shorter CSP. Across all subjects with SCZ, CSP was inversely associated with negative symptoms, and SICI was inversely associated with positive symptoms. Conclusions: These results confirm that unmedicated SCZ patients have CI deficits and that clozapine treatment is associated with potentiation of GABAB-inhibitory neurotransmission and reduced GABAA inhibitory neurotransmission. Also, the differential associations among SICI, CSP, and clinical symptom dimensions suggest that GABAA- and GABAB-mediated CI might have different roles in the pathophysiology of symptoms of schizophrenia. [Copyright &y& Elsevier]

Background: The present study evaluated the effectiveness and safety of clozapine versus “high-dose” olanzapine in treatment-refractory adolescents with schizophrenia. Methods: Children, ages 10–18 years, who met DSM-IV criteria for schizophrenia and who were resistant or intolerant to at least two antipsychotic drugs were randomized to receive 12 weeks of double-blind flexibly dosed treatment with clozapine (n = 18) or “high-dose” olanzapine (up to 30 mg/day) (n = 21). The primary efficacy measure was response (improvement), defined as a decrease of 30% or more in total Brief Psychiatric Rating Scale score from baseline and a Clinical Global Impression Scale improvement rating of “1” (very much improved) or “2” (much improved). Results: Significantly more clozapine-treated adolescents met response criteria (66%) compared with olanzapine-treated subjects (33%). Clozapine was superior to olanzapine in terms of reduction of the psychosis cluster scores and negative symptoms from baseline to end point. However, both treatments were associated with significant weight-gain and related metabolic abnormalities. Conclusions: This double-blind randomized comparison of two second-generation antipsychotic drugs for treatment-refractory adolescents with schizophrenia supports clozapine as the agent of choice. The development of interventions to limit weight gain and metabolic side effects are needed to enhance the risk-benefit profile for both study treatments. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Background: Atypical antipsychotics have been assessed for normalization effects on deficient sensory gating as indexed by prepulse inhibition (PPI) in schizophrenics with generally positive, although somewhat conflicting, results. Methods: We tested the acute effect of clozapine on startle, PPI, and attention, working memory, and executive functioning in 28 healthy male volunteers with low versus high PPI levels using a placebo-controlled within-subject design. Results: Clozapine significantly increased PPI levels obtained at short lead intervals of 60 and 120 msec in subjects with low PPI performance but showed no effect in subjects with high PPI. Clozapine also caused a mild cognitive impairment on attention and pattern recognition memory tests. No correlations between cognitive measures and PPI performance were found. Moreover, low and high PPI performers were shown to exhibit stable levels of PPI across three separate nondrug testing days. Conclusions: Clozapine increases sensorimotor gating in healthy subjects with low but not high PPI levels in a manner comparable to that seen in clozapine-treated schizophrenia patients. Healthy subjects with low PPI level in combination with genetic studies may provide a translational model to elucidate the neuronal basis of PPI deficits and to test the efficacy of novel antipsychotic medication. [Copyright &y& Elsevier]

Background: Maternal viral infection is associated with increased risk for schizophrenia. It is hypothesized that the maternal immune response to viruses may influence fetal brain development and lead to schizophrenia. Methods: To mimic a viral infection, the synthetic double strand RNA polyriboinosinic-polyribocytidilic acid (poly I:C) was administered into pregnant mice. Behavioral evaluations (thigmotaxis, methamphetamine [MAP]-induced hyperactivity, novel-object recognition test [NORT]), sensorimotor gating (prepulse inhibition [PPI]), and biochemical evaluation of the dopaminergic function of the offspring of phosphate-buffered saline (PBS)-treated dams (PBS-mice) and that of poly I:C-treated dams (poly I:C-mice) were examined. Results: In juveniles, no difference was found between the poly I:C-mice and PBS-mice. However, in adults, the poly I:C-mice exhibited attenuated thigmotaxis, greater response in MAP-induced (2 mg/kg) hyperlocomotion, deficits in PPI, and cognitive impairment in NORT compared with the PBS-mice. Cognitive impairment in the adult poly I:C-mice could be improved by subchronic administration of clozapine (5.0 mg/kg) but not haloperidol (.1 mg/kg). Increased dopamine (DA) turnover and decreased receptor binding of D2-like receptors, but not D1-like receptors, in the striatum were found in adult poly I:C-mice. Conclusions: Prenatal poly I:C administration causes maturation-dependent increased subcortical DA function and cognitive impairment in the offspring, indicating a neurodevelopmental animal model of schizophrenia. [Copyright &y& Elsevier]

Background: Central serotonin2C (5-HT2C) receptors are known to play a role in the mechanism of action of the antipsychotic drugs (APDs) clozapine and haloperidol. However, evidence for the involvement of the constitutive activity of 5-HT2C receptors in the dopamine (DA)ergic effects of APDs is lacking in vivo. Methods: Using in vivo microdialysis in halothane-anesthetized rats, we assessed the ability of selective 5-HT2C compounds to modulate the release of DA induced by haloperidol and clozapine in the nucleus accumbens and striatum. Results: Both APDs induced a dose-dependent increase in accumbal and striatal DA extracellular levels. The effect of .01 mg/kg haloperidol was potentiated by the 5-HT2C inverse agonist SB 206553 (5 mg/kg) but unaltered by the 5-HT2C antagonists SB 243213 and SB 242084 (1 mg/kg). Conversely, the effect of 1 mg/kg clozapine, a dose able to reverse the decrease in DA outflow induced by the 5-HT2C agonist Ro 60-0175 (3 mg/kg), was unaffected by SB 206553 but blocked by SB 243213 (1 mg/kg) and SB 242084 (.3 and 1 mg/kg). Conclusions: These results show that clozapine and haloperidol differentially alter the constitutive activity of 5-HT2C receptors and suggest that clozapine behaves as a 5-HT2C inverse agonist in vivo. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Background: Clozapine shows superior efficacy in schizophrenia and enhances prefrontal dopamine (DA) output like other atypical, but not typical, antipsychotic drugs (APDs). Clinical data also suggest an improved effect of typical APDs in schizophrenia by adjunctive treatment with low doses of 3,4-dihydroxyphenylalanine (L-dopa), but experimental support is scarce, and the underlying mechanisms are poorly understood. Methods: Antipsychotic efficacy of the D2 antagonist raclopride with or without adjunctive treatment with a low dose of L-dopa was assessed with the conditioned avoidance response paradigm. Extrapyramidal side effects were scored by the catalepsy test. Finally, in vivo microdialysis was used to measure DA efflux in the prefrontal cortex and the nucleus accumbens. Results: A low dose of L-dopa (3 mg/kg) combined with benserazide, an inhibitor of peripheral DOPA decarboxylase, significantly enhanced the antipsychotic-like effect of raclopride without any associated catalepsy. L-dopa/benserazide alone had no effect. In contrast to raclopride alone, combined L-dopa/raclopride also produced a much larger increase in DA output in the prefrontal cortex than in the nucleus accumbens. Conclusions: These data support the clinical observation that low-dose L-dopa might improve the effect of typical APDs in schizophrenia and indicate that increased prefrontal DA output per se enhances the antipsychotic effect of typical APDs. [Copyright &y& Elsevier]

Background: Antipsychotic drugs modulate N-methyl-D-aspartate (NMDA) receptor function in animals. The novel single photon emission tomography (SPET) radiotracer [123I]CNS-1261 binds to the PCP/MK-801 intrachannel site of the NMDA receptor, allowing the noninvasive estimation of NMDA receptor activity in living humans. We used [123I]CNS-1261 to determine whether binding to the NMDA receptor intrachannel PCP/MK-801 site is affected by schizophrenia or by treatment with typical antipsychotics and clozapine in vivo. Methods: Three groups of schizophrenia patients were recruited—drug free (n = 5), typical antipsychotic treated (n = 7), and clozapine treated (n = 9)—as well as a control group of healthy normal volunteers (n = 13). All underwent [123I]CNS-1261 SPET scanning. Total volume of distribution of [123I]CNS-1261 was determined within predefined user-independent regions of interest after alignment of all images to a common template. Results: There was no apparent difference in total volume of distribution of [123I]CNS-1261 in drug-free patients relative to healthy control subjects. A nonsignificant reduction in total volume of distribution was observed in typical antipsychotic treated patients. A significant decline in total volume of distribution of [123I]CNS-1261 was observed in all examined brain regions in the clozapine-treated patient group relative to healthy control subjects (p &#60; .005). Conclusions: Clozapine treatment resulted in a global reduction in [123I]CNS-1261 binding to the NMDA receptor intrachannel PCP/MK-801 site in vivo. This supports an effect of the drug on glutamatergic systems that could be exploited for future antipsychotic drug discovery. [Copyright &y& Elsevier]

Background: Compelling evidence indicates that kappa opioid receptor (KOR) agonists produce perceptual distortions in animals and humans, yet the mechanism of action and clinical relevance of such effects remain unclear. Since abnormalities in preattentional functions and informational processing are hypothesized to underlie psychotic disorders, the present study has been designed to assess the role of KOR on sensorimotor gating. Methods: The effects of the selective KOR agonist U50488 were evaluated on the behavioral paradigm of prepulse inhibition (PPI) of the acoustic startle reflex (ASR). Results: U50488 (1.25, 2.5, and 5 mg/kg, subcutaneous [SC]) induced a dose-dependent reduction of PPI, which was efficiently prevented by the selective KOR antagonist norbinaltorphimine (nor-BNI, 10 mg/kg, SC), as well as by the atypical antipsychotic clozapine (5, 8 mg/kg, intraperitoneal [IP]) but not by the typical antipsychotic haloperidol (.1, .5 mg/kg, IP). Conversely, nor-BNI (10 mg/kg, SC) failed to reverse the PPI disruption mediated by both apomorphine (.25 mg/kg, SC) and dizocilpine (.1 mg/kg, SC). Conclusions: Our results support a pivotal role of KOR in the regulation of preattentional functions and sensorimotor gating, pointing to these receptors as a possible neurobiological substrate especially relevant to the clusters of psychosis unresponsive to typical antipsychotics. [Copyright &y& Elsevier]

Background: Molecular adaptations are believed to contribute to the mechanism of action of antipsychotic drugs (APDs). We attempted to establish common gene regulation patterns induced by chronic treatment with APDs. Methods: Gene expression analysis was performed with the Affymetrix U34A array in the frontal cortex (FC) and the striatum of rats chronically treated with two concentrations of either clozapine or haloperidol. Key data were verified with real-time quantitative polymerase chain reaction. Results: Many genes in the FC affected by APD-treatment contribute to similar functions. mRNAs coding for synaptic vesicle docking- and microtubule-associated proteins were upregulated; mRNAs for serine-threonine protein phosphatases were downregulated, whereas the serine-threonine kinases protein kinase A, protein kinase C, and calcium/calmodulin kinase II alpha and IV were upregulated, indicating increased potential for protein phosphorylation. In the striatum, altered gene expression was less focused on genes of particular function or location, and the high concentration of haloperidol had a different gene expression profile than any of the other APD treatments. Conclusion: We found an increase in the transcription of genes coding for proteins involved in synaptic plasticity and synaptic activity in the FC. We furthermore found that the gene expression profile of APDs is different between FC and striatum. [Copyright &y& Elsevier]

Background: Mitogen-activated protein kinase (MAPK) signaling pathways respond to dopaminergic and serotonergic agents and mediate short- and long-term effects of intracellular signaling in neurons. Here we show that the antipsychotic agent, clozapine, selectively activates the MEK/ERK MAPK pathway, and inhibition of this pathway reverses clozapine’s actions in the conditioned avoidance response (CAR) paradigm, a rodent behavioral assay of antipsychotic activity. Methods: Phosphorylation patterns of MAPK pathway enzymes were determined by quantitative immunoblot analysis and immunohistochemistry of rat prefrontal cortex. Kinase inhibitors were used to assess the role of MAPK signaling pathways in mediating clozapine-induced suppression of CAR. Results: Clozapine administration selectively increased phosphorylation of MEK1/2 but had no effect on p38 or JNK phosphorylation. Pretreatment with the 5-HT2A agonist (+/–)–2,5-dimethoxy-4-iodoamphetamine hydrochloride blocked the clozapine-induced increase in MEK1/2 phosphorylation. Immunohistochemistry revealed that clozapine treatment elevated the number of cells in the prefrontal cortex positive for phosphoERK, the downstream substrate of MEK1/2. Prior administration of MEK1/2 inhibitors U0126 or Sl327, or ERK inhibitor 5-iodotubercidin, reversed suppression of CAR induced by clozapine, whereas administration of vehicle, JNK or p38 inhibitors (L-JNK-1 and SB203580, respectively) had no effect. Inhibition of kinases upstream to MEK1/2 (PI-3K, PKC, and CaMKII) by administration of LY294002, bisindolylmaleimide, or KN-62, respectively, also reversed clozapine-induced suppression of CAR. Conclusions: These data support the hypothesis that the MEK/ERK signal transduction cascade participates in clozapine’s antipsychotic actions. [Copyright &y& Elsevier]

Background: D-serine, a selective full agonist at the glycine site of N-methyl-d-aspartate glutamate receptor, might presently be the compound of choice for counteracting the hypothesized dysfunction of this receptor class in schizophrenia. Studies performed with Taiwanese patients indicate that D-serine significantly improves schizophrenia symptoms when used as adjuvant to conventional neuroleptics but not to clozapine. We assessed the efficacy and safety of D-serine adjuvant treatment for Occidental schizophrenia patients treated with newer atypical antipsychotics. Methods: Thirty-nine risperidone- or olanzapine-treated schizophrenia patients participated in a double-blind, placebo-controlled, 6-week crossover trial with 30 mg/kg/day D-serine added to their antipsychotic medication. Measures of clinical efficacy and side effects were determined biweekly throughout the study. Clinical laboratory parameters and amino acid serum levels were monitored. Results: D-serine administration induced increased serine serum levels (p < .001) and resulted in significant (p < .001) improvements in negative, positive, cognitive, and depression symptoms, as measured by the Positive and Negative Syndrome Scale. For approximately one third of the sample, D-serine treatment resulted in significant (>20%) reductions in Brief Psychiatric Rating Scale total scores. D-serine was well tolerated, and no detrimental changes in clinical laboratory parameters were noted. Conclusions: These findings 1) indicate that risperidone and olanzapine efficacy might be augmented with D-serine adjuvant treatment; 2) confirm D-serine efficacy against main schizophrenia symptom domains; and 3) warrant the assessment of D-serine antipsychotic monotherapy for this illness. [Copyright &y& Elsevier]

Recent studies show that endogenous levels of kynurenic acid (KYNA) are increased in the cerebrospinal fluid of schizophrenic patients. Prepulse inhibition (PPI) of the acoustic startle reflex is an operational measure of sensorimotor gating that is reduced in neuropsychiatric disorders, such as schizophrenia. Previous studies show that administration of N-methyl-d-aspartate (NMDA) receptor antagonists, such as phencyclidine or MK-801, leads to deficits in sensorimotor gating that mimic those observed in schizophrenic patients.The present study examined the effects of the endogenous NMDA receptor antagonist KYNA on startle and PPI in rats. Elevation of endogenous brain levels of KYNA was achieved through intraperitoneal (IP) administration of kynurenine (100 mg/kg), the precursor of KYNA, or by intravenous administration of PNU 156561A (10 mg/kg).A fourfold increase in brain KYNA levels, as induced by kynurenine or PNU 156561A, significantly reduced PPI. There were no differences in startle magnitudes between control rats and drug-treated rats. The disruption of PPI was restored by administration of the antipsychotic drugs haloperidol (.2 mg/kg, IP) or clozapine (7.5 mg/kg, IP).The present results suggest that brain KYNA serves as an endogenous modulator of PPI and are consistent with the hypothesis that KYNA contributes to the pathophysiology of schizophrenia. [Copyright &y& Elsevier]

: BackgroundChronic exposure to stressful events precipitates or exacerbates many neuropsychiatric disorders, including depression and schizophrenia. Evidence suggests that treatment with the atypical antipsychotic drugs olanzapine or clozapine results in a superior amelioration of the anxious and depressive symptoms that accompany schizophrenia relative to therapy with classical antipsychotics such as haloperidol. Moreover, olanzapine and clozapine, but not haloperidol, increase the brain content of neuroactive steroids. The effects of olanzapine and clozapine on the stress-induced increase in dopamine output in the rat cerebral cortex have now been compared with that of haloperidol.: MethodsRats chronically treated (3 weeks, once a day) with each drug were exposed to foot-shock stress or injected with a single dose of the anxiogenic benzodiazepine receptor ligand FG7142, and dopamine release was then measured in the prefrontal cortex by vertical microdialysis.: ResultsLong-term administration of olanzapine or clozapine prevented or markedly inhibited, respectively, the increase in the extracellular dopamine concentration induced by foot shock; haloperidol had no such effect. Chronic olanzapine treatment also blocked the effect of FG7142 on dopamine output.: ConclusionsThe reduction in the sensitivity of cortical dopaminergic neurons to stress shown to be elicited by treatment with olanzapine or clozapine may contribute to the anxiolytic actions of these drugs. [Copyright &y& Elsevier]

: BackgroundStudies have shown that neuroleptics regulate expression of the transcription factor FosB/ΔFosB in the striatum, including the accumbens and caudate-putamen; however, the striatum is also divided into another structural dimension, the striosome and matrix compartments. The precise distribution of FosB/ΔFosB induced by chronic neuroleptics in these striatal compartments is poorly understood.: MethodsRats received either single acute injections or chronic injections of clozapine (0 or 20 mg/kg, intraperitoneally [IP]), olanzapine (0 or 5 mg/kg, IP), or haloperidol (0 or 1.5 mg/kg, IP) for 25 days. The levels and compartmental distribution of FosB/ΔFosB were examined.: ResultsChronic clozapine induced clustered FosB/ΔFosB expression within striosomes of the caudate-putamen. This pattern was due to increased levels of FosB/ΔFosB in striosomes within the ventrolateral caudate-putamen and reduced levels of basal FosB/ΔFosB in the matrix in the entire caudate-putamen. In contrast, chronic haloperidol increased FosB/ΔFosB equally within the matrix and striosomes throughout the entire caudate-putamen. Chronic olanzapine induced an intermediate pattern.: ConclusionsThe relative absence of FosB/ΔFosB expression in the matrix correlates with the lack of parkinsonism of atypical neuroleptics. Expression of FosB/ΔFosB in the matrix may contribute to parkinsonism of typical neuroleptics. [Copyright &y& Elsevier]

: BackgroundSelective localization of dopamine D4 receptors in the prefrontal cortex and preferential affinity of clozapine for the dopamine D4 receptor over the D2 receptor led to the hypothesis that the superior efficacy of clozapine may be mediated via blockade of the D4 receptor. This hypothesis was tested by evaluating sonepiprazole, a selective D4 dopamine antagonist, in schizophrenia patients.: MethodsWe treated 467 hospitalized schizophrenia patients with scores of ≥ 60 on the Positive and Negative Syndrome Scale (PANSS) with sonepiprazole, olanzapine, or placebo once daily for 6 weeks. The primary efficacy end point was the mean change from baseline in the PANSS total score at 6 weeks. Secondary efficacy end points were the mean change from baseline in the PANSS factor scores, the Brief Psychiatric Rating Scale score, the Clinical Global Impressions Severity of Illness score, and the Calgary Depression Scale score.: ResultsNo statistically significant differences were observed between placebo and any sonepiprazole dose on the primary or any secondary end point after 6 weeks of treatment. Statistically significant differences, favoring olanzapine over placebo, were observed on all efficacy end points but the Calgary Depression Scale.: ConclusionsSonepiprazole was ineffective for the treatment of patients with schizophrenia. [Copyright &y& Elsevier]

: BackgroundBased on the phenomenologic similarity between symptoms of drug withdrawal and the negative symptoms of schizophrenia (e.g., anhedonia), we hypothesized that treatment with clozapine may be effective against nicotine and amphetamine withdrawal.: MethodsA rate-independent discrete-trial threshold procedure was used to assess brain stimulation reward in rats prepared with electrodes in the lateral hypothalamus. Somatic signs of nicotine withdrawal were also assessed.: ResultsClozapine administration (.75 or 1.5 mg/kg) during nicotine or amphetamine withdrawal did not affect the threshold elevations associated with drug withdrawal. The .75 mg/kg clozapine dose reversed the increased number of somatic signs of nicotine withdrawal. Ten days of clozapine treatment (3 mg/kg/b.i.d.) before exposure to nicotine prevented the threshold elevations in a subset of rats and the increases in somatic signs in all subjects. Fourteen-day pretreatment with clozapine (6 mg/kg/day) decreased the duration of amphetamine withdrawal.: ConclusionsCorrelational analyses indicated that the ability of clozapine to prevent the affective aspects of drug withdrawal depended on low sensitivity to acute clozapine under baseline conditions. The results are consistent with the clinical situation where clozapine is partially effective against the negative symptoms of schizophrenia and more effective in some individuals than others. These results indicate that lack of sensitivity to the initial negative effects of clozapine may predict its a subsequent therapeutic response. Finally, the data suggest that there may be commonalities in the neurosubstrates mediating affective aspects of drug withdrawal and the negative symptoms of schizophrenia. [Copyright &y& Elsevier]

: BackgroundThe gene DRD4, coding for dopamine receptor D4, was considered a candidate for association with schizophrenia based on its upregulation in postmortem schizophrenic brain and affinity for clozapine. Many studies sought allelic association of a 48-base-pair repeat in DRD4 exon 3 with schizophrenia, but found no strong evidence for a relationship. The present work sought to determine if this observation reflected the true absence of association or the low power of individual studies.: MethodsWe performed four meta-analyses, sequentially considering the two-, four-, and seven-repeat alleles as risk alleles, and then considering repeat length of the 48-base-pair segment as a risk factor. Each meta-analysis included at least 2300 cases and 2100 controls from 14–16 studies.: ResultsThe pooled odds ratio from each analysis approximated 1.0, and none were significant. Heterogeneity was not observed, although gender moderated the effects of repeat length and the seven-repeat allele.: ConclusionsDespite over 90% power to detect a significant odds ratio of 1.4 or less, none was observed. This polymorphism seems not to influence risk for most schizophrenia cases; however, a sex-dependent relationship, or a role in some clinical features of the disorder, cannot be excluded and should be pursued experimentally. [Copyright &y& Elsevier]

: BackgroundEnhanced ability to reliably identify risk factors for suicidal behavior permits more focused decisions concerning treatment interventions and support services, with potential reduction in lives lost to suicide.: MethodsThis study followed 980 patients at high risk for suicide in a multicenter prospective study for 2 years after randomization to clozapine or olanzapine. A priori predictors related to diagnosis, treatment resistance, and clinical constructs of disease symptoms were evaluated as possible predictors of subsequent suicide-related events.: ResultsTen baseline univariate predictors were identified. Historical predictors were diagnosis of schizoaffective disorder, history or current use at baseline of alcohol or substance abuse, cigarette smoking, number of lifetime suicide attempts, and the number of hospitalizations in the previous 36 months to prevent suicide. Predictive clinical features included greater baseline scores on the InterSePT scale for suicidal thinking, the Covi Anxiety Scale, the Calgary Depression Scale (CDS), and severity of Parkinsonism. Subsequent multivariate analysis revealed the number of hospitalizations in the previous 36 months, baseline CDS, severity of Parkinson’s, history of substance abuse, and lifetime suicide attempts. Clozapine, in general, was more effective than olanzapine in decreasing the risk of suicidality, regardless of risk factors present.: ConclusionsThis is the first prospective analysis of predictors of suicide risk in a large schizophrenic and schizoaffective population judged to be at high risk for suicide. Assessment of these risk factors may aid clinicians in evaluating risk for suicidal behaviors so that appropriate interventions can be made. [Copyright &y& Elsevier]

: BackgroundUsing positron emission tomography (PET) with 15O water, we compared regional cerebral blood flow (rCBF) patterns induced by clozapine or haloperidol in individuals with schizophrenia. Based on the known clinical characteristics of each drug, we hypothesized that brain regions where the drugs show similar rCBF patterns are among those mediating their antipsychotic actions; whereas, regions where the drugs produce different rCBF patterns are among those mediating their different drug actions, namely, haloperidol’s motor side effects or clozapine’s unique therapeutic action.: MethodsPersons with schizophrenia were scanned using PET with 15O water, first after withdrawal of all psychotropic medication (n = 6), then again after treatment with therapeutic doses of haloperidol (n = 5) or clozapine (n = 5).: ResultsBoth drugs increased rCBF in the ventral striatum and decreased rCBF in hippocampus and ventrolateral frontal cortex. The rCBF increase associated with haloperidol was greater than that with clozapine in the dorsal and ventral striatum; the rCBF increase with clozapine was greater than that with haloperidol in cortical regions, including anterior cingulate and dorsolateral frontal cortex.: ConclusionsThese data suggest that the rCBF increase in ventral striatum and/or the decrease in hippocampus and/or ventrolateral frontal cortex mediate a common component of antipsychotic action of these drugs. The increased rCBF in dorsal striatum by haloperidol could well be associated with its prominent motor side effects, whereas the increased rCBF in the anterior cingulate or dorsolateral frontal cortex may mediate the superior antipsychotic action of clozapine. The proposals based on these preliminary observations require further study. [Copyright &y& Elsevier]

Background: Recent evidence suggests that effects upon glutamatergic transmission may contribute to the therapeutic action of certain atypical antipsychotic agents.Methods: Glutamate concentrations were measured in serum and were estimated (Glx/Cr) in cingulate cortex by proton magnetic resonance spectroscopy (MRS) in schizophrenia patients while they were being treated with conventional neuroleptics and then 8 weeks after switching to olanzapine. Serum glutamate concentrations were obtained from 11 subjects, and MRS estimates of Glx/Cr were available from 10 subjects at both time points.Results: Serum glutamate concentrations significantly increased after the switch from conventional agents to olanzapine; brain glutamate (Glx/Cr) did not change significantly; however, brain glutamate (Glx/Cr) concentrations increased significantly in patients who exhibited an improvement in negative symptoms with olanzapine compared with patients with no change or worsening of negative symptoms.Conclusions: Comparisons performed following the switch from conventional agents to olanzapine are consistent with previous studies of clozapine and provide additional preliminary evidence supporting the hypothesis that effects on excitatory amino acid activity may contribute to olanzapine’s efficacy for treating negative symptoms. [ABSTRACT FROM AUTHOR]