Asenapine effects on cognitive and monoamine dysfunction elicited by subchronic phencyclidine administration

Decoding effects of psychoactive drugs in a high-dimensional space of eye movements in monkeys

Oculomotor behavior has been shown to be correlated with mental disorders in clinics, making it promising for disease diagnosis. Here we developed a thorough oculomotor test toolkit, involving saccade, smooth pursuit, and fixation, allowing the examination of multiple oculomotor parameters in monkey models induced by psychoactive drugs. Eye movements were recorded after daily injections of phencyclidine (PCP) (3.0 mg/kg), ketamine (0.8 mg/kg) or controlled saline in two macaque monkeys. Both drugs led to robust reduction in accuracy and increment in reaction time during high cognitive-demanding tasks. Saccades, smooth pursuit, and fixation stability were also significantly impaired. During fixation, the involuntary microsaccades exhibited increased amplitudes and were biased toward the lower visual field. Pupillary response was reduced during cognitive tasks. Both drugs also increased sensitivity to auditory cues as reflected in auditory evoked potentials (AEPs). Thus, our animal model induced by psychoactive drugs produced largely similar abnormalities to that in patients with schizophrenia. Importantly, a classifier based on dimension reduction and machine learning could reliably identify altered states induced by different drugs (PCP, ketamine and saline, accuracy = 93%). The high performance of the classifier was reserved even when data from one monkey were used for training and testing the other subject (averaged classification accuracy = 90%). Thus, despite heterogeneity in baseline oculomotor behavior between the two monkeys, our model allows data transferability across individuals, which could be beneficial for future evaluation of pharmaceutical or physical therapy validity.

Methamphetamine exacerbates pathophysiology of traumatic brain injury at high altitude. Neuroprotective effects of nanodelivery of a potent antioxidant compound H-290/51

Military personnel are often exposed to high altitude (HA, ca. 4500-5000m) for combat operations associated with neurological dysfunctions. HA is a severe stressful situation and people frequently use methamphetamine (METH) or other psychostimulants to cope stress. Since military personnel are prone to different kinds of traumatic brain injury (TBI), in this review we discuss possible effects of METH on concussive head injury (CHI) at HA based on our own observations. METH exposure at HA exacerbates pathophysiology of CHI as compared to normobaric laboratory environment comparable to sea level. Increased blood-brain barrier (BBB) breakdown, edema formation and reductions in the cerebral blood flow (CBF) following CHI were exacerbated by METH intoxication at HA. Damage to cerebral microvasculature and expression of beta catenin was also exacerbated following CHI in METH treated group at HA. TiO2-nanowired delivery of H-290/51 (150mg/kg, i.p.), a potent chain-breaking antioxidant significantly enhanced CBF and reduced BBB breakdown, edema formation, beta catenin expression and brain pathology in METH exposed rats after CHI at HA. These observations are the first to point out that METH exposure in CHI exacerbated brain pathology at HA and this appears to be related with greater production of oxidative stress induced brain pathology, not reported earlier.

Universal Nature of Drug Treatment Responses in Drug-Tissue-Wide Model-Animal Experiments Using Tensor Decomposition-Based Unsupervised Feature Extraction

Gene expression profiles of tissues treated with drugs have recently been used to infer clinical outcomes. Although this method is often successful from the application point of view, gene expression altered by drugs is rarely analyzed in detail, because of the extremely large number of genes involved. Here, we applied tensor decomposition (TD)-based unsupervised feature extraction (FE) to the gene expression profiles of 24 mouse tissues treated with 15 drugs. TD-based unsupervised FE enabled identification of the common effects of 15 drugs including an interesting universal feature: these drugs affect genes in a gene-group-wide manner and were dependent on three tissue types (neuronal, muscular, and gastroenterological). For each tissue group, TD-based unsupervised FE enabled identification of a few tens to a few hundreds of genes affected by the drug treatment. These genes are distinctly expressed between drug treatments and controls as well as between tissues in individual tissue groups and other tissues. We also validated the assignment of genes to individual tissue groups using multiple enrichment analyses. We conclude that TD-based unsupervised FE is a promising method for integrated analysis of gene expression profiles from multiple tissues treated with multiple drugs in a completely unsupervised manner.

Effects of Ketamine Administration on Auditory Information Processing in the Neocortex of Nonhuman Primates

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, exerts broad effects on consciousness and perception. Since NMDA receptor antagonists induce cognitive impairments, ketamine has been used for translational research on several psychiatric diseases, such as schizophrenia. Whereas the effects of ketamine on cognitive functions have been extensively studied, studies on the effects of ketamine on simple sensory information processing remain limited. In this study, we investigated the cortex-wide effects of ketamine administration on auditory information processing in nonhuman primates using whole-cortical electrocorticography (ECoG). We first recorded ECoG from awake monkeys on presenting auditory stimuli of different frequencies or different durations. We observed auditory evoked responses (AERs) across the cortex, including in frontal, parietal, and temporal areas, while feature-specific responses were obtained around the temporal sulcus. Next, we examined the effects of ketamine on cortical auditory information processing. We conducted ECoG recordings from monkeys that had been administered anesthetic doses of ketamine from 10 to 180 min following administration. We observed significant changes in stimulus feature-specific responses. Electrodes showing a frequency preference or offset responses were altered following ketamine administration, while those of the AERs were not strongly influenced. However, the frequency preference of a selected electrode was not significantly altered by ketamine administration over time following administration, while the imbalances in the onset and offset persisted over the course of 150 min following ketamine administration in all three monkeys. These results suggest that ketamine affects the ability to distinguish between sound frequency and duration in different ways. In conclusion, future research on the NMDA sensitivity of cortical wide sensory information processing may provide a new perspective into the development of nonhuman primate models of psychiatric disorders.

Asenapine maleate normalizes low frequency oscillatory deficits in a neurodevelopmental model of schizophrenia

Asenapine maleate (AM) is an atypical antipsychotic that, unlike many other antipsychotics, shows some efficacy in treating cognitive dysfunction in schizophrenia. Normal cognitive function has long since been associated with high frequency neuronal oscillations. However, recent research has highlighted the potential importance of low frequency oscillations. Here, the impact of AM on low frequency neural oscillatory activity was evaluated in the methylazoxymethanol acetate (MAM) rat model system used for the study schizophrenia, and the oscillatory signatures compared to those of haloperidol (HAL) and clozapine (CLZ). AM and CLZ normalized low frequency spectral power deficits in the prefrontal cortex, while HAL and AM reversed corticostriatal and corticocortical delta coherence deficits. However, only chronic AM administration normalized corticostriatal and corticocortical delta coherence deficits between 3-4 Hz. These findings support the idea that antipsychotic-induced amelioration of both delta coherence and power may be important for therapeutic efficacy in treating the cognitive deficits inherent in schizophrenia.

[Translational behavioral research using common marmosets in the psychiatric field]

The drug discovery activities for novel compounds with the superior efficacies to current drugs have been largely unsuccessful in the psychiatric field. One of the main reasons is the lack of appropriate behavioral assays and animal models for psychiatric disorders. Since the prefrontal cortex has great roles in their pathophysiology, non-human primate common marmosets with the well-developed prefrontal cortex would be useful as experimental animals in the future translational research. To measure objectively and quantitatively the psychiatric symptoms like motivational deficits, negative affective bias and cognitive impairments in patients with schizophrenia or major depressive disorder, the clinical laboratory tasks have been developed. The development of marmoset behavioral paradigms, which may correspond to the clinical laboratory tasks, have been progressed for the translational research. On the other hand, there are still limitations to develop the marmoset models resembling the pathophysiology of psychiatric disorders. We review the current state and future perspective of translational behavioral research using marmosets.

The detour paradigm in animal cognition

In this paper, we review one of the oldest paradigms used in animal cognition: the detour paradigm. The paradigm presents the subject with a situation where a direct route to the goal is blocked and a detour must be made to reach it. Often being an ecologically valid and a versatile tool, the detour paradigm has been used to study diverse cognitive skills like insight, social learning, inhibitory control and route planning. Due to the relative ease of administrating detour tasks, the paradigm has lately been used in large-scale comparative studies in order to investigate the evolution of inhibitory control. Here we review the detour paradigm and some of its cognitive requirements, we identify various ecological and contextual factors that might affect detour performance, we also discuss developmental and neurological underpinnings of detour behaviors, and we suggest some methodological approaches to make species comparisons more robust.

The α2C-adrenoceptor antagonist, ORM-10921, has antipsychotic-like effects in social isolation reared rats and bolsters the response to haloperidol

Early studies suggest that selective α2C-adrenoceptor (AR)-antagonism has anti-psychotic-like and pro-cognitive properties. However, this has not been demonstrated in an animal model of schizophrenia with a neurodevelopmental construct. The beneficial effects of clozapine in refractory schizophrenia and associated cognitive deficits have, among others, been associated with its α2C-AR modulating activity. Altered brain-derived neurotrophic factor (BDNF) has been linked to schizophrenia and cognitive deficits. We investigated whether the α2C-AR antagonist, ORM-10921, could modulate sensorimotor gating and cognitive deficits, as well as alter striatal BDNF levels in the social isolation reared (SIR) model of schizophrenia, comparing its effects to clozapine and the typical antipsychotic, haloperidol, the latter being devoid of α2C-AR-activity. Moreover, the ability of ORM-10921 to augment the effects of haloperidol on the above parameters was also investigated. Animals received subcutaneous injection of either ORM-10921 (0.01mg/kg), clozapine (5mg/kg), haloperidol (0.2mg/kg), haloperidol (0.2mg/kg)+ORM-10921 (0.01mg/kg) or vehicle once daily for 14days, followed by assessment of novel object recognition (NOR), prepulse inhibition (PPI) of startle response and striatal BDNF levels. SIR significantly attenuated NOR memory as well as PPI, and reduced striatal BDNF levels vs. social controls. Clozapine, ORM-10921 and haloperidol+ORM-10921, but not haloperidol alone, significantly improved SIR-associated deficits in PPI and NOR, with ORM-10921 also significantly improving PPI deficits vs. haloperidol-treated SIR animals. Haloperidol+ORM-10921 significantly reversed reduced striatal BDNF levels in SIR rats. α2C-AR-antagonism improves deficits in cognition and sensorimotor gating in a neurodevelopmental animal model of schizophrenia and bolsters the effects of a typical antipsychotic, supporting a therapeutic role for α2C-AR-antagonism in schizophrenia.

Detour Behavior of Mice Trained with Transparent, Semitransparent and Opaque Barriers

Detour tasks are commonly used to study problem solving skills and inhibitory control in canids and primates. However, there is no comparable detour test designed for rodents despite its significance for studying the development of executive skills. Furthermore, mice offer research opportunities that are not currently possible to achieve when primates are used. Therefore, the aim of the study was to translate the classic detour task to mice and to compare obtained data with key findings obtained previously in other mammals. The experiment was performed with V-shaped barriers and was based on the water escape paradigm. The study showed that an apparently simple task requiring mice to move around a small barrier constituted in fact a challenge that was strongly affected by the visibility of the target. The most difficult task involved a completely transparent barrier, which forced the mice to resolve a conflict between vision and tactile perception. The performance depended both on the inhibitory skills and on previous experiences. Additionally, all mice displayed a preference for one side of the barrier and most of them relied on the egocentric strategy. Obtained results show for the first time that the behavior of mice subjected to the detour task is comparable to the behavior of other mammals tested previously with free-standing barriers. This detailed characterization of the detour behavior of mice constitutes the first step toward the substitution of rodents for primates in laboratory experiments employing the detour task.

Asenapine: A Review in Schizophrenia

Asenapine (Saphris(®), Sycrest(®)) is an atypical antipsychotic that is administered sublingually twice daily and is approved for schizophrenia in the USA, Japan and other countries, but not in the EU. This article reviews the pharmacology, clinical efficacy and tolerability profile of asenapine in the treatment of adults with schizophrenia. Clinical trials with asenapine have demonstrated efficacy in terms of both positive and negative symptoms of schizophrenia, although findings have not always been consistent. Across three short-term (6-week) studies in acute schizophrenia (including one in Asian patients), asenapine was generally superior to placebo and had broadly similar efficacy to active controls in improving total scores on the Positive and Negative Syndrome Scale. A meta-analysis of four short-term trials with asenapine (that also included a negative study and a failed trial) also showed significant benefit with asenapine over placebo. In longer-term trials and extensions (up to ≈3 years' duration), asenapine was effective relative to placebo in preventing relapse in schizophrenia, but was less effective than olanzapine in patients with schizophrenia or schizoaffective disorder (according to intent-to-treat LOCF analysis). However, in two trials in patients with persistent negative symptoms of schizophrenia, asenapine and olanzapine were similarly effective in reducing negative symptoms at week 26, with asenapine providing better results than olanzapine at week 52 in one of the extensions. The most frequently reported adverse events with asenapine are somnolence, akathisia and oral hypoesthesia. Although potentially associated with more extrapyramidal symptoms, asenapine appears to have less weight gain and metabolic effects than some other antipsychotic agents, such as olanzapine.

The effects of a 5-HT5A receptor antagonist in a ketamine-based rat model of cognitive dysfunction and the negative symptoms of schizophrenia

Serotonin (5-HT) receptors still represent promising targets for the development of novel multireceptor or stand-alone antipsychotic drugs with a potential to ameliorate cognitive impairments and negative symptoms in schizophrenia. The 5-HT5A receptor, one of the least known members of the serotonin receptor family, has also drawn attention in this regard. Although the antipsychotic efficacy of 5-HT5A antagonists is still equivocal, recent experimental data suggest the cognitive-enhancing activity of this strategy. The aim of the present study was to evaluate pro-cognitive and pro-social efficacies of the 5-HT5A receptor antagonist in a rat pharmacological model of schizophrenia employing the administration of the NMDA receptor antagonist, ketamine. The ability of SB-699551 to reverse ketamine-induced cognitive deficits in the attentional set-shifting task (ASST) and novel object recognition task (NORT) was examined. The compound's efficacy against ketamine-induced social withdrawal was assessed in the social interaction test (SIT) and in the social choice test (SCT). The results demonstrated the efficacy of SB-699551 in ameliorating ketamine-induced impairments on the ASST and NORT. Moreover, the tested compound also enhanced set-shifting performance in cognitively unimpaired control rats and improved object recognition memory in conditions of delay-induced natural forgetting. The pro-social activity of SB-699551 was demonstrated on both employed paradigms, the SIT and SCT. The present study suggests the preclinical efficacy of a strategy based on the blockade of 5-HT5A receptors against schizophrenia-like cognitive deficits and negative symptoms. The utility of this receptor as a target for improvement of cognitive and social dysfunctions warrants further studies.

The subchronic phencyclidine rat model: relevance for the assessment of novel therapeutics for cognitive impairment associated with schizophrenia

RATIONALE

Current treatments for schizophrenia have modest, if any, efficacy on cognitive dysfunction, creating a need for novel therapies. Their development requires predictive animal models. The N-methyl-D-aspartate (NMDA) hypothesis of schizophrenia indicates the use of NMDA antagonists, like subchronic phencyclidine (scPCP) to model cognitive dysfunction in adult animals.

OBJECTIVES

The objective of this study was to assess the scPCP model by (1) reviewing published findings of scPCP-induced neurochemical changes and effects on cognitive tasks in adult rats and (2) comparing findings from a multi-site study to determine scPCP effects on standard and touchscreen cognitive tasks.

METHODS

Across four research sites, the effects of scPCP (typically 5 mg/kg twice daily for 7 days, followed by at least 7-day washout) in adult male Lister Hooded rats were studied on novel object recognition (NOR) with 1-h delay, acquisition and reversal learning in Morris water maze and touchscreen-based visual discrimination.

RESULTS

Literature findings showed that scPCP impaired attentional set-shifting (ASST) and NOR in several labs and induced a variety of neurochemical changes across different labs. In the multi-site study, scPCP impaired NOR, but not acquisition or reversal learning in touchscreen or water maze. Yet, this treatment regimen induced locomotor hypersensitivity to acute PCP until 13-week post-cessation.

CONCLUSIONS

The multi-site study confirmed that scPCP impaired NOR and ASST only and demonstrated the reproducibility and usefulness of the touchscreen approach. Our recommendation, prior to testing novel therapeutics in the scPCP model, is to be aware that further work is required to understand the neurochemical changes and specificity of the cognitive deficits.

Primate phencyclidine model of schizophrenia: sex-specific effects on cognition, brain derived neurotrophic factor, spine synapses, and dopamine turnover in prefrontal cortex

BACKGROUND

Cognitive deficits are a core symptom of schizophrenia, yet they remain particularly resistant to treatment. The model provided by repeatedly exposing adult nonhuman primates to phencyclidine has generated important insights into the neurobiology of these deficits, but it remains possible that administration of this psychotomimetic agent during the pre-adult period, when the dorsolateral prefrontal cortex in human and nonhuman primates is still undergoing significant maturation, may provide a greater understanding of schizophrenia-related cognitive deficits.

METHODS

The effects of repeated phencyclidine treatment on spine synapse number, dopamine turnover and BDNF expression in dorsolateral prefrontal cortex, and working memory accuracy were examined in pre-adult monkeys.

RESULTS

One week following phencyclidine treatment, juvenile and adolescent male monkeys demonstrated a greater loss of spine synapses in dorsolateral prefrontal cortex than adult male monkeys. Further studies indicated that in juvenile males, a cognitive deficit existed at 4 weeks following phencyclidine treatment, and this impairment was associated with decreased dopamine turnover, decreased brain derived neurotrophic factor messenger RNA, and a loss of dendritic spine synapses in dorsolateral prefrontal cortex. In contrast, female juvenile monkeys displayed no cognitive deficit at 4 weeks after phencyclidine treatment and no alteration in dopamine turnover or brain derived neurotrophic factor messenger RNA or spine synapse number in dorsolateral prefrontal cortex. In the combined group of male and female juvenile monkeys, significant linear correlations were detected between dopamine turnover, spine synapse number, and cognitive performance.

CONCLUSIONS

As the incidence of schizophrenia is greater in males than females, these findings support the validity of the juvenile primate phencyclidine model and highlight its potential usefulness in understanding the deficits in dorsolateral prefrontal cortex in schizophrenia and developing novel treatments for the cognitive deficits associated with schizophrenia.

Evidence that aetiological risk factors for psychiatric disorders cause distinct patterns of cognitive deficits

Schizophrenia and bipolar disorder are associated with neurocognitive symptoms including deficits in attentional set shifting (changing attentional focus from one perceptual dimension to another) and reversal learning (learning a reversed stimulus/outcome contingency). Maternal infection during gestation and chronically flattened glucocorticoid rhythm are aetiological risk factors for schizophrenia and bipolar disorder. We hypothesised that these factors are causative in the neurocognitive deficits observed in schizophrenia and bipolar disorder. Here we used maternal immune activation (MIA) as a rat model of maternal infection, and sub-chronic low dose corticosterone treatment as a rat model of flattened glucocorticoid rhythm. For comparison we examined the effects of sub-chronic phencyclidine - a widely used rodent model of schizophrenia pathology. The effects of these three treatments on neurocognition were explored using the attentional set shifting task - a multistage test of executive functions. As expected, phencyclidine treatment selectively impaired set shifting ability. In contrast, MIA caused a marked and selective impairment of reversal learning. Corticosterone treatment impaired reversal learning but in addition also impaired rule abstraction and prevented the animals from forming an attentional set. The reversal learning deficits induced by MIA and corticosterone treatment were due to increases in non-perseverative rather than perseverative errors. Our data indicate that the cognitive deficits of schizophrenia and bipolar disorder may be explained by aetiological factors including maternal infection and glucocorticoid abnormalities and moreover suggest that the particular spectrum of cognitive deficits in individual patients may depend on the specific underlying aetiology of the disorder.

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.

Translating the N-methyl-D-aspartate receptor antagonist model of schizophrenia to treatments for cognitive impairment in schizophrenia

The N-methyl-D-aspartate receptor (NMDAR) antagonists, phencyclidine (PCP), dizocilpine (MK-801), or ketamine, given subchronically (sc) to rodents and primates, produce prolonged deficits in cognitive function, including novel object recognition (NOR), an analog of human declarative memory, one of the cognitive domains impaired in schizophrenia. Atypical antipsychotic drugs (AAPDs) have been reported to improve declarative memory in some patients with schizophrenia, as well as to ameliorate and prevent the NOR deficit in rodents following scNMDAR antagonist treatment. While the efficacy of AAPDs to improve cognitive impairment in schizophrenia (CIS) is limited, at best, and controversial, single doses of all currently available AAPDs so far tested transiently restore NOR in rodents following scNMDAR antagonist treatment. Typical antipsychotic drugs (APDs), e.g. haloperidol and perphenazine, are ineffective in this rodent model, and may be less effective as treatments of some domains of CIS. Serotonergic mechanisms, including, but not limited to serotonin (5-HT)2A and 5-HT7 antagonism, 5-HT(1A), and GABA(A) agonism, contribute to the efficacy of the AAPDs in the scNMDAR antagonist rodent models, which are relevant to the loss of GABA interneuron/hyperglutamate hypothesis of the etiology of CIS. The ability of sub-effective doses of the atypical APDs to ameliorate NOR in the scNMDAR-treated rodents can be restored by the addition of a sub-effective dose of the 5-HT(1A) partial agonist, tandospirone, or the 5-HT7 antagonist, SB269970. The mGluR2/3 agonist, LY379268, which itself is unable to restore NOR in the scNMDAR-treated rodents, can also restore NOR when given with lurasidone, an AAPD. Enhancing cortical and hippocampal dopamine and acetylcholine efflux, or both, may contribute to the restoration of NOR by the atypical APDs. Importantly, co-administration of lurasidone, tandospirone, or SB269970, with PCP, to rodents, at doses 5-10 fold greater than those acutely effective to restore NOR following scNMDAR treatment, prevents the effect of scPCP to produce an enduring deficit in NOR. This difference in dosage may be relevant to utilizing AAPDs to prevent the onset of CIS in individuals at high risk for developing schizophrenia. The scNMDAR paradigm may be useful for identifying possible means to treat and prevent CIS.

Repeated asenapine treatment produces a sensitization effect in two preclinical tests of antipsychotic activity

Among several commonly used atypical antipsychotic drugs, olanzapine and risperidone cause a sensitization effect in the conditioned avoidance response (CAR) and phencyclidine (PCP)-induced hyperlocomotion paradigms--two well established animal tests of antipsychotic drugs, whereas clozapine causes a tolerance effect. Asenapine is a novel antipsychotic drug recently approved for the treatment of schizophrenia and manic disorders. It shares several receptor binding sites and behavioral features with other atypical antipsychotic drugs. However, it is not clear what type of repeated effect (sensitization or tolerance) asenapine would induce, and whether such an effect is transferrable to other atypicals. In this study, male adult Sprague-Dawley rats were first repeatedly tested with asenapine (0.05, 0.10 or 0.20 mg/kg, sc) for avoidance response or PCP (3.20 mg/kg, sc)-induced hyperlocomotion daily for 5 consecutive days. After 2-3 days of retraining/drug-free recovery, they were then challenged with asenapine (0.10 mg/kg, sc), followed by olanzapine (0.50 mg/kg, sc) and clozapine (2.50 mg/kg, sc). During the 5-day drug test period (the induction phase), repeated asenapine treatment progressively increased its inhibition of avoidance response and PCP-induced hyperlocomotion in a dose-dependent fashion. On the asenapine and olanzapine challenge tests (the expression phase), rats previously treated with asenapine still showed significantly lower avoidance response and lower PCP-induced hyperlocomotion than those previously treated with vehicle. An increased reactivity to clozapine challenge in prior asenapine-treated rats was also found in the PCP-induced hyperlocomotion test. These findings suggest that asenapine is capable of inducing a sensitization effect and a cross-sensitization to olanzapine and clozapine (to a lesser extent). Because the behavioral profile of asenapine in both tests is similar to that of olanzapine, but different from that of clozapine, we suggest that asenapine resembles olanzapine to a greater extent than clozapine in its therapeutic and side effect profiles.

Asenapine in bipolar I disorder: evidence and place in patient management

Asenapine is a new second-generation antipsychotic approved in September 2010 by the European Medicines Agency for the treatment of bipolar disorder. It demonstrated significant efficacy compared with placebo in acute mania or mixed episodes as monotherapy or adjunctive therapy to mood stabilizers (lithium or valproate). Early improvement was noted at day 2 and was strongly associated with response and remission at week 3. Asenapine also appeared effective in treating acute mania in older patients with bipolar disorder. Post hoc analyses of asenapine showed efficacy in treating depressive symptoms during manic or mixed episodes compared with placebo. The efficacy of asenapine in patients with acute mania appeared to remain constant during maintenance treatment. Asenapine was reasonably well tolerated, especially with regard to metabolic effects. There were minimal signs of glucose elevation or lipid changes and the risk of weight gain appeared limited. The prolactin elevation was smaller than other antipsychotic comparators. Only oral hypoesthesia occurred as a new adverse event compared with other second-generation antipsychotics. Asenapine presents several advantages over other second-generation antipsychotics, such as sublingual formulation, early efficacy and good metabolic tolerability. This tolerability profile confirms the heterogeneity of the second-generation antipsychotic class and supports the view of some authors for the need to re-evaluate the boundaries of this group.

Iloperidone, asenapine and lurasidone: a primer on their current status

INTRODUCTION

Three newer atypical antipsychotic drugs were FDA-approved in 2009 and 2010 in the following order: iloperidone, asenapine and lurasidone. The three drugs are indicated for the treatment of acute schizophrenia. Asenapine is also approved for treatment of manic or mixed episodes associated with bipolar I disorder, for the maintenance treatment of schizophrenia and as an adjunctive therapy with lithium or valproate for the acute treatment of manic or mixed episodes associated with bipolar I disorder in adults.

AREAS COVERED

This review compares and contrasts the current preclinical, clinical, safety and tolerability profiles of the three newer drugs, as reported in published preclinical and clinical studies, product labels, poster presentations and press releases.

EXPERT OPINION

Preclinical studies have reported that the three drugs have variable affinities for a wide range of neurotransmitter receptors, and are active in animal models predictive of antipsychotic activity. Asenapine is the first antipsychotic to be administered sublingually, whereas iloperidone requires titration to minimize orthostatic hypotension. Asenapine and lurasidone are associated with dose-related akathisia, whereas iloperidone is not. The three drugs appear to have relatively benign metabolic profiles. The availability of the three novel antipsychotics should provide additional options for improved treatment of schizophrenia and other psychotic disorders.

[Asenapine in bipolar disorder: efficacy, safety and place in clinical practice]

Asenapine is a new second-generation antipsychotic (SGA) approved in September 2010 by the European Medicines Agency for the treatment of bipolar disorder. It was significantly more effective than placebo in acute mania or mixed episodes as monotherapy or adjunctive therapy to mood stabilizers (lithium or valproate). Early improvement was seen at day-2 (significant difference with placebo) and was strongly associated with week-3 response and remission. These suggest that the observation of an early improvement in the first week may be clinically an useful tool for individual treatment adjustment during the early course of treatment. Post-hoc analyses of asenapine studies showed significantly better effects on improving depressive symptoms associated with manic symptoms, and physical health related quality of life dimensions as compared to placebo. Asenapine differs from the other SGAs by a good tolerability profile, in particular in terms of metabolic profile. However, it seems to have a significant though moderate link with the occurrence of sedation. This new tolerance profile greatly broadens the scope of SGAs and supports the view of some authors that the term SGA is now outdated. Other therapeutic perspectives of asenapine are being assessed, in particular in specific population (pediatric and elderly patients).

Quetiapine and Buspirone Both Elevate Cortical Levels of Noradrenaline and Dopamine In vivo, but Do Not have Synergistic Effects

Decreased cognitive ability is a significant problem in schizophrenia, and it has been proposed that augmentation of antipsychotics with 5HT(1A) receptor agonists may improve cognitive performance. Clinical studies have been mixed but there have been no studies specifically examining the effects of combining the atypical antipsychotic quetiapine with the 5HT(1A) receptor partial agonist, buspirone on monoamine release. This is of interest given previous evidence that monoamine release can alter cognition in schizophrenia. In the present study we measured in vivo levels of monoamines in the frontal cortex of Sprague Dawley rats and examined if buspirone (2.5 mg/kg i.p.), altered monoamine release both when given alone and when combined with quetiapine (10 mg/kg i.p.). We found that serotonin levels were not altered by either drug, either alone or in combination. In contrast, both buspirone and quetiapine monotherapy significantly increased release of noradrenaline (112 and 160% respectively) and dopamine (169 and 191% respectively) compared to controls. However, there were no additional increases in in vivo monoamine release when the combination of these drugs were given. One possible explanation for these negative findings could be that the intrinsic 5HT(1A) agonist activity of quetiapine on its own is of such significance that it is not further enhanced by buspirone. These findings do not support clinical studies combining buspirone and quetiapine, if these were to be used on the basis of enhanced monoamine neurotransmission. These findings may also have implications for the atypical antipsychotic drugs in development which combine dopamine D(2) antagonism with 5HT(1A) partial agonism.