Mechanisms of action of second generation antipsychotic drugs in schizophrenia: insights from brain imaging studies

Efficacy, acceptability and side-effects of oral versus long-acting- injectables antipsychotics: Systematic review and network meta-analysis

Long-acting injectable antipsychotics (LAIs) are primarily used for relapse prevention, but in some settings and situations, they may also be useful for acute treatment of schizophrenia. We conducted a systematic review and frequentist network meta-analysis of randomized-controlled trials (RCTs), focusing on adult patients in the acute phase of schizophrenia. Interventions were risperidone, paliperidone, aripiprazole, olanzapine, and placebo, administered either orally or as LAI. We synthesized data on overall symptoms, complemented by 17 other efficacy and tolerability outcomes. Confidence in the evidence was assessed with the Confidence-in-Network-Meta-Analysis-framework (CINeMA). We included 115 RCTs with 25,550 participants. All drugs were significantly more efficacious than placebo with the following standardized mean differences and their 95 % confidence intervals: olanzapine LAI -0.66 [-1.00; -0.33], risperidone LAI -0.59[-0.73;-0.46], olanzapine oral -0.55[-0.62;-0.48], aripiprazole LAI -0.54[-0.71; -0.37], risperidone oral -0.48[-0.55;-0.41], paliperidone oral -0.47[-0.58;-0.37], paliperidone LAI -0.45[-0.57;-0.33], aripiprazole oral -0.40[-0.50; -0.31]. There were no significant efficacy differences between LAIs and oral formulations. Sensitivity analyses of the primary outcome overall symptoms largely confirmed these findings. Moreover, some side effects were less frequent under LAIs than under their oral counterparts. Confidence in the evidence was moderate for most comparisons. LAIs are efficacious for acute schizophrenia and may have some benefits compared to oral formulations in terms of side effects. These findings assist clinicians with insights to weigh the risks and benefits between oral and injectable agents when treating patients in the acute phase.

Atypical antipsychotics antagonize GABAA receptors in the ventral tegmental area GABA neurons to relieve psychotic behaviors

Psychosis is an abnormal mental condition that can cause patients to lose contact with reality. It is a common symptom of schizophrenia, bipolar disorder, sleep deprivation, and other mental disorders. Clinically, antipsychotic medications, such as olanzapine and clozapine, are very effective in treatment for psychosis. To investigate the neural circuit mechanism that is affected by antipsychotics and identify more selective therapeutic targets, we employed a strategy by using these effective antipsychotics to identify antipsychotic neural substrates. We observed that local injection of antipsychotics into the ventral tegmental area (VTA) could reverse the sensorimotor gating defects induced by MK-801 injection in mice. Using in vivo fiber photometry, electrophysiological techniques, and chemogenetics, we found that antipsychotics could activate VTA gamma-aminobutyric acid (GABA) neurons by blocking GABAA receptors. Moreover, we found that the VTAGABA nucleus accumbens (NAc) projection was crucially involved in such antipsychotic effects. In summary, our study identifies a novel therapeutic target for the treatment of psychosis and underscores the utility of a 'bedside-to-bench' approach for identifying neural circuits that influence psychotic disorders.

Antidepressive Effectiveness of Amisulpride, Aripiprazole, and Olanzapine in Patients With Schizophrenia Spectrum Disorders: A Secondary Outcome Analysis of a Pragmatic, Randomized Trial (BeSt InTro)

BACKGROUND

Depressive symptoms are frequent in schizophrenia and associated with a poorer outcome. Currently, the optimal treatment for depressive symptoms in schizophrenia remains undetermined. Amisulpride, aripiprazole, and olanzapine all have antidepressive pharmacodynamic properties, ranging from serotonergic affinities to limbic dopaminergic selectivity. Consequently, in a 12-month pragmatic, randomized clinical trial, we aimed to investigate differences in antidepressive effectiveness among amisulpride, aripiprazole, and olanzapine as a secondary outcome, measured by change in the Calgary Depression Scale for Schizophrenia sum score in patients within the schizophrenia spectrum.

METHODS

Psychotic patients within the schizophrenia spectrum were included, and effectiveness was analyzed with latent growth curve modeling.

RESULTS

Of the 144 patients, 51 (35%) were women, the mean age was 31.7 (SD 12.7), and 39% were antipsychotic naive. At inclusion, 68 (47%) participants had a Calgary Depression Scale for Schizophrenia sum score >6, indicating severe depressive symptoms. Across the 12-month follow-up, there was a depressive symptom reduction in all medication groups, but no statistically significant differences between the study drugs. Separate analyses of the subcohort with elevated depressive symptoms at inclusion also failed to find differences in depressive symptom reduction between study drugs. The reduction in depressive symptoms mainly occurred within 6 weeks after randomization.

CONCLUSIONS

There was a reduction in depressive symptoms under treatment with amisulpride, aripiprazole, and olanzapine in acutely psychotic patients with schizophrenia spectrum disorder, but no differences between the drugs.

Identification and Characterization of ML321: A Novel and Highly Selective D2 Dopamine Receptor Antagonist with Efficacy in Animal Models That Predict Atypical Antipsychotic Activity

We have developed and characterized a novel D2R antagonist with exceptional GPCR selectivity - ML321. In functional profiling screens of 168 different GPCRs, ML321 showed little activity beyond potent inhibition of the D2R and to a lesser extent the D3R, demonstrating excellent receptor selectivity. The D2R selectivity of ML321 may be related to the fact that, unlike other monoaminergic ligands, ML321 lacks a positively charged amine group and adopts a unique binding pose within the orthosteric binding site of the D2R. PET imaging studies in non-human primates demonstrated that ML321 penetrates the CNS and occupies the D2R in a dose-dependent manner. Behavioral paradigms in rats demonstrate that ML321 can selectively antagonize a D2R-mediated response (hypothermia) while not affecting a D3R-mediated response (yawning) using the same dose of drug, thus indicating exceptional in vivo selectivity. We also investigated the effects of ML321 in animal models that are predictive of antipsychotic efficacy in humans. We found that ML321 attenuates both amphetamine- and phencyclidine-induced locomotor activity and restored pre-pulse inhibition (PPI) of acoustic startle in a dose-dependent manner. Surprisingly, using doses that were maximally effective in both the locomotor and PPI studies, ML321 was relatively ineffective in promoting catalepsy. Kinetic studies revealed that ML321 exhibits slow-on and fast-off receptor binding rates, similar to those observed with atypical antipsychotics with reduced extrapyramidal side effects. Taken together, these observations suggest that ML321, or a derivative thereof, may exhibit ″atypical″ antipsychotic activity in humans with significantly fewer side effects than observed with the currently FDA-approved D2R antagonists.

Glutamate in the Dorsolateral Prefrontal Cortex in Patients With Schizophrenia: A Meta-analysis of 1H-Magnetic Resonance Spectroscopy Studies

BACKGROUND

To date, there is no systematic overview of glutamate in the dorsolateral prefrontal cortex (DLPFC) of patients with schizophrenia. Here, we meta-analyzed case-control studies of high-field proton magnetic resonance spectroscopy (¹H-MRS) investigating glutamate in DLPFC. Additionally, we estimated variance ratios to investigate homo/heterogeneity.

METHODS

Preregistration of the study was performed on September 20, 2019. The predefined literature search on PubMed comprised articles with search terms (magnetic resonance spectroscopy OR MRS) AND (glutamate OR glut∗ OR GLX) AND (schizophrenia OR psychosis OR schizophren∗). Meta-analyses with a fixed- and random-effects model with inverse variance method, DerSimonian-Laird estimator for τ², and Cohen's d were calculated. For differences in variability, we calculated a random-effects model for measures of variance ratios. The primary study outcome was the difference in glutamate in the DLPFC in cases versus controls. Secondary outcomes were differences in variability.

RESULTS

The quantitative analysis comprised 429 cases and 365 controls. Overall, we found no group difference (d = 0.03 [95% confidence interval (CI), -0.20 to 0.26], z = 0.28, p = .78). Sensitivity analysis revealed an effect for medication status (Q = 8.35, p = .039), i.e., increased glutamate in antipsychotic-naïve patients (d = 0.46 [95% CI, 0.08 to 0.84], z = 2.37, p = .018). Concerning variance ratios, we found an effect of medication status (Q = 16.95, p < .001) due to lower coefficient of variation ratio (CVR) in medication-naïve patients (logCVR = -0.49 [95% CI, -0.78 to -0.20], z = -3.33, p < .001). In studies with medicated patients, we found higher CVR (logCVR = 0.22 [95% CI, 0.06 to 0.39], z = 2.67; p = .008).

CONCLUSIONS

We carefully interpret the higher levels and lower variability in cortical glutamate in antipsychotic-naïve patients as a possible key factor resulting from a putative allostatic mechanism. We conclude that care has to be taken when evaluating metabolite levels in clinical samples in which medication might confound findings.

Reproducing the dopamine pathophysiology of schizophrenia and approaches to ameliorate it: a translational imaging study with ketamine

Patients with schizophrenia show increased striatal dopamine synthesis capacity in imaging studies. The mechanism underlying this is unclear but may be due to N-methyl-D-aspartate receptor (NMDAR) hypofunction and parvalbumin (PV) neuronal dysfunction leading to disinhibition of mesostriatal dopamine neurons. Here, we develop a translational mouse model of the dopamine pathophysiology seen in schizophrenia and test approaches to reverse the dopamine changes. Mice were treated with sub-chronic ketamine (30 mg/kg) or saline and then received in vivo positron emission tomography of striatal dopamine synthesis capacity, analogous to measures used in patients. Locomotor activity was measured using the open-field test. In vivo cell-type-specific chemogenetic approaches and pharmacological interventions were used to manipulate neuronal excitability. Immunohistochemistry and RNA sequencing were used to investigate molecular mechanisms. Sub-chronic ketamine increased striatal dopamine synthesis capacity (Cohen's d = 2.5) and locomotor activity. These effects were countered by inhibition of midbrain dopamine neurons, and by activation of PV interneurons in pre-limbic cortex and ventral subiculum of the hippocampus. Sub-chronic ketamine reduced PV expression in these cortical and hippocampal regions. Pharmacological intervention with SEP-363856, a novel psychotropic agent with agonism at trace amine receptor 1 (TAAR1) and 5-HT_1A receptors but no appreciable action at dopamine D₂ receptors, significantly reduced the ketamine-induced increase in dopamine synthesis capacity. These results show that sub-chronic ketamine treatment in mice mimics the dopaminergic alterations in patients with psychosis, that this requires activation of midbrain dopamine neurons, and can be ameliorated by activating PV interneurons and by a TAAR1/5-HT_1A agonist. This identifies novel therapeutic approaches for targeting presynaptic dopamine dysfunction in patients with schizophrenia and effects of ketamine relevant to its therapeutic use for  treating major depression.

A Review of Antipsychotics and Priapism

INTRODUCTION

Pharmacologically induced priapism is now the most common cause of priapism, with approximately 50% of drug-related priapism being attributed to antipsychotic usage. The majority of pharmacologic priapism is believed to result in ischemic priapism (low flow), which may lead to irreversible complications, such as erectile dysfunction. It is imperative that prescribing physicians be aware of potentially inciting medications.

OBJECTIVES

To identify medications, specifically antipsychotics, associated with priapism and prolonged erections and understand the rates and treatment of these side effects.

METHODS

A PubMed search of all articles available on the database relating to priapism, prolonged erections, and antipsychotics was performed.

RESULTS

Various typical and atypical antipsychotic drugs (APDs) have been implicated in pharmacologically induced priapism. In addition to dopaminergic and serotoninergic receptors, APDs have affinities for a wide array of other receptors in the central nervous system, including histaminergic, noradrenergic, and cholinergic receptors. Although the exact mechanism is unknown, the most commonly proposed mechanism of priapism associated with APDs is α-adrenergic blockade in the corpora cavernosa of the penis. Priapism appears in only a small fraction of men using medications with α1-receptor-blocking properties, indicating differential sensitivities to the α-blocking effect among men, and/or additional risk factors that may contribute to the development of priapism. The best predictor for the subsequent development of priapism is a past history of having prolonged and painless erections. The acute management algorithm of APD-induced priapism is the same as for other causes of low-flow priapism.

CONCLUSION

Clinicians should educate patients treated with antipsychotics about the potential for priapism and its sequelae including permanent erectile dysfunction. Appropriate patient education will raise awareness, encourage early reporting, and help reduce the long-term consequences associated with priapism through early intervention. Hwang T, Shah T,Sadeghi-NejadH. A Review of Antipsychotics and Priapism. Sex Med Rev 2021;9:464-471.

Efficacy and safety of brexpiprazole in acute management of psychiatric disorders: a meta-analysis of randomized controlled trials

Brexpiprazole is a new atypical antipsychotic for schizophrenia management and as adjunct in major depressive disorder (MDD). We searched randomized controlled trials (RCT) to review brexpiprazole efficacy and tolerability in acute management of schizophrenia and MDD using PubMed, EUDRACT, ClinicalTrials.gov and Cochrane Central Register of Controlled Trials. A meta-analysis was conducted using the identified 14 RCT to assess its efficacy using positive and negative syndrome scale (PANSS), clinical global impressions - severity of illness (CGI-S), personal and social performance scale (PSP), Montgomery-Åsberg depression rating scale (MADRS), Sheehan disability scale (SDS) and Hamilton depression rating scale (HDRS17). The mean difference comparing brexpiprazole and placebo were PANSS -4.48, CGI-S -0.23 and PSP 3.24 favoring brexpiprazole. Compared to aripiprazole and quetiapine, brexpiprazole showed similar efficacy. In MDD, brexpiprazole showed efficacy compared to placebo demonstrated by MADRS -1.25, SDS -0.37 and HDRS17 -1.28. Brexpiprazole was associated with side effects including akathisia risk ratio (RR) = 1.72; weight increase RR = 2.74 and somnolence RR = 1.87. Compared to 4 mg, brexpiprazole 2 mg was associated with less risk of akathisia and somnolence. Brexpiprazole demonstrated significant improvements in schizophrenia and MDD and is well-tolerated; however, associated with akathisia and somnolence. These findings will guide psychiatrists and pharmacists in their clinical role for supporting psychiatric patients care.

Modulating NMDA receptors to treat MK-801-induced schizophrenic cognition deficit: effects of clozapine combining with PQQ treatment and possible mechanisms of action

BACKGROUND

Clozapine has remarkable efficacy on both negative and cognitive symptoms of schizophrenia due to its slight activation of NMDA receptor. In fact, much evidence to the contrary. NMDAR is a complex containing specific binding sites, which are regulated to improve negative symptoms and cognitive deficits associated with individuals affected by schizophrenia. PQQ is a powerful neuroprotectant that specifically binds with NMDA receptors in the brain to produce beneficial physiological and cognitive outcomes. The aim of this study was to enhance NMDAR function and improve cognitive ability in schizophrenia by PQQ combined with clozapine.

METHODS

Rats were divided into four groups (n = 5) including control (saline), model (MK-801, 0.5 mg·kg^- 1·d^- 1), atypical antipsychotic (MK-801 (0.5 mg·kg^- 1·d^- 1) + Clozapine (1.0 mg·kg^- 1·d^- 1), and co-agonist NMDA receptor (MK-801 (0.5 mg·kg^- 1·d^- 1) + Clozapine (0.5 mg·kg^- 1·d^- 1) + PQQ (1.0 μg·kg^- 1·d^- 1) group. Each group of rats was injected subcutaneously every day for 6 weeks. Behavior test, including stereotyped behavior, locomotor hyperactivity, learning and memory, was performed. The Western blot assay was performed to analyze the expression of GSK-3β, Akt, NMDAR1, and MGLUR in rat hippocampus.

RESULTS

Results indicated that clozapine and PQQ combination therapy can improve MK801-induced schizophrenia behavior including stereotyped behavior, locomotor hyperactivity and cognitive impairment. Furthermore, we found that modulating NMDA receptors could ameliorate the memory impairments in Mk-801 induced schizophrenia rats by reducing the expression of NMDAR1 and MGLUR3, decreasing hippocampal tau hyperphosphorylation and inhibiting apoptosis through Akt /GSK-3β signaling pathway.

CONCLUSIONS

These findings suggest that combination therapy for enhancing NMDA receptors may be able to rescue cognition deficit in schizophrenia. More studies are needed to better elucidate these mechanisms.

Treatment resistant schizophrenia: Clinical, biological, and therapeutic perspectives

Treatment resistant schizophrenia (TRS) refers to the significant proportion of schizophrenia patients who continue to have symptoms and poor outcomes despite treatment. While many definitions of TRS include failure of two different antipsychotics as a minimum criterion, the wide variability in inclusion criteria has challenged the consistency and reproducibility of results from studies of TRS. We begin by reviewing the clinical, neuroimaging, and neurobiological characteristics of TRS. We further review the current treatment strategies available, addressing clozapine, the first-line pharmacological agent for TRS, as well as pharmacological and non-pharmacological augmentation of clozapine including medication combinations, electroconvulsive therapy, repetitive transcranial magnetic stimulation, deep brain stimulation, and psychotherapies. We conclude by highlighting the most recent consensus for defining TRS proposed by the Treatment Response and Resistance in Psychosis Working Group, and provide our overview of future perspectives and directions that could help advance the field of TRS research, including the concept of TRS as a potential subtype of schizophrenia.

Potential Utility of Biased GPCR Signaling for Treatment of Psychiatric Disorders

Tremendous advances have been made recently in the identification of genes and signaling pathways associated with the risks for psychiatric disorders such as schizophrenia and bipolar disorder. However, there has been a marked reduction in the pipeline for the development of new psychiatric drugs worldwide, mainly due to the complex causes that underlie these disorders. G-protein coupled receptors (GPCRs) are the most common targets of antipsychotics such as quetiapine and aripiprazole, and play pivotal roles in controlling brain function by regulating multiple downstream signaling pathways. Progress in our understanding of GPCR signaling has opened new possibilities for selective drug development. A key finding has been provided by the concept of biased ligands, which modulate some, but not all, of a given receptor's downstream signaling pathways. Application of this concept raises the possibility that the biased ligands can provide therapeutically desirable outcomes with fewer side effects. Instead, this application will require a detailed understanding of the mode of action of antipsychotics that drive distinct pharmacologies. We review our current understanding of the mechanistic bases for multiple signaling modes by antipsychotics and the potential of the biased modulators to treat mental disorders.

Insomnia in patients with schizophrenia: current understanding and treatment options

In patients with schizophrenia, insomnia is a common yet often overlooked comorbidity. With sleep disturbances inextricably linked to increased severity of schizophrenia and worsening clinical outcomes, insomnia is an important therapeutic target within this patient population. Thus, through a review of the current literature, this paper reiterates the important etiological link between these two conditions, while evaluating the safety, efficacy, and limitations of current therapeutic options for the treatment of comorbid insomnia in schizophrenia. Despite the continued use of benzodiazepine receptor agonists (BZRAs) for insomnia, the use of other therapies such as Cognitive Behavioral Therapy for Insomnia (CBT-I) and suvorexant warrants increased consideration. More large-scale clinical trials are needed to assess the efficacy of such therapeutic options in the schizophrenia patient population.

Long-term effects of iloperidone on cerebral dopamine receptor subtypes

The atypical antipsychotic drug iloperidone has high affinity for a wide range of neurotransmitter receptors, including dopaminergic (DA), serotonergic, and adrenergic receptors. We examined the long-term effects of multiple doses of iloperidone on DA D1 , D2 , D3 , and D4 receptor subtypes. Sprague-Dawley adult rats (n = 8/group) received daily intraperitoneal injections of iloperiodone (0.5, 1, or 5 mg/kg) or vehicle for 4 weeks. Receptor autoradiography quantified the levels of DA receptors in medial prefrontal cortex (MPC), dorsolateral frontal cortex (DFC), caudate putamen (CPu), nucleus accumbens (NAc), and hippocampus (HIP). Four weeks of iloperidone treatment at 5 mg/kg significantly increased D1 receptors in NAc (36%) and CPu (38%). Iloperidone (1.5 and 5 mg/kg) dose-dependently increased D2 receptors in MPC (37 and 47%) and HIP (32 and 40%). Only the high dose of iloperidone (5 mg/kg) increased D2 receptors in NAc (39%) and CPu (38%). Repeated treatment with iloperidone (1.5 and 5 mg/kg) increased D4 receptors in the NAc (39 and 78%), CPu (42 and 83%) and HIP (54 and 72%). The three doses of iloperidone failed to alter D3 receptors in the brain regions examined in this study. These results suggest that iloperidone exerts region- and dose-specific effects on forebrain DA receptor subtypes, which may contribute to its therapeutic benefits in improving the positive and negative symptoms of schizophrenia with minimal extrapyramidal side effects.

The novel atypical antipsychotic cariprazine demonstrates dopamine D2 receptor-dependent partial agonist actions on rat mesencephalic dopamine neuronal activity

Aim

Cariprazine, a dopamine D₃‐preferring D₃/D₂ receptor partial agonist, is FDA approved for the treatment of schizophrenia and acute manic or mixed episodes of bipolar disorder. This study used in vivo electrophysiological techniques in anesthetized rats to determine cariprazine's effect on dopaminergic cell activity in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc).

Methods

Extracellular recordings of individual dopaminergic neurons were performed after oral or intravenous administration of cariprazine, the D₃ receptor antagonist SB 277011A, the D₂ receptor antagonist L741,626, and/or the D₃ receptor agonist PD 128,907.

Results

Acute oral treatment with cariprazine significantly increased and chronic cariprazine significantly decreased the number of spontaneously firing dopaminergic neurons in the VTA, but not in the SNc. Intravenous administration of cariprazine partially but significantly inhibited dopaminergic neuronal firing in both regions, which was prevented by L741,626 but not SB 277011A. In both VTA and SNc, cariprazine, SB 277011A, and L741,626 significantly antagonized the suppression of dopamine cell firing elicited by PD 128,907.

Conclusions

Cariprazine significantly modulates the number of spontaneously active VTA dopamine neurons and moderately suppresses midbrain dopamine neuronal activity. The contribution of dopamine D₂ receptors to cariprazine's in vivo effects is prevalent and that of D₃ receptors is less apparent.

Reliability and Validity of the Short Version of Udvalg for Kliniske Undersogelser in Antipsychotic Treatment

The aim of this study was to develop a reliable and valid short version of the Udvalg for Kliniske Undersogelser (UKU) to efficiently evaluate the side effects of antipsychotics in patients with schizophrenia. This multi-site study included 10 hospitals, which included 331 inpatients and outpatients diagnosed with schizophrenia. UKU, Clinical Global Impression-Severity (CGI-S), Personal and Social Performance (PSP) and dosage of paliperidone were collected. The predictive validity of the UKU-short version, as well as that of the CGI-S, PSP and paliperidone dosages, was analyzed using structural equation modeling (SEM), latent growth models (LGM), and confirmatory factor analysis to test its content and construct validity. The UKU-short included nine-items of sedation, reduced sleep, rigidity, tremor, akathisia, headache, reduced salivation, constipation and orthostatic dizziness, and has good construct and content validity over time. Confirmatory factor analysis showed good construct validity, with the psychic, neurological and autonomic side effect dimensions having correlations between 0.60 and 0.71. The predictive validity of the short-version UKU for psychiatric symptoms (CGI-S), quality of life (PSP) and dosage showed that the effects of drug dosage were negligible, and only neurological side effects were associated with psychiatric symptoms and quality of life. The UKU-short showed good content, construct and predictive validity. It is a more time-efficient instrument than the original UKU. This study only included patients treated with paliperidone, larger scale studies is needed to validate the UKU-short in detection of side effects in routine clinical practice to prevent non-adherence in patients with schizophrenia.

Post-zygotic genomic changes in glutamate and dopamine pathway genes may explain discordance of monozygotic twins for schizophrenia

Background

Monozygotic twins are valuable in assessing the genetic vs environmental contribution to diseases. In the era of complete genome sequences, they allow identification of mutational mechanisms and specific genes and pathways that offer predisposition to the development of complex diseases including schizophrenia.

Methods

We sequenced the complete genomes of two pairs of monozygotic twins discordant for schizophrenia (MZD), including one representing a family tetrad. The family specific complete sequences have allowed identification of post zygotic mutations between MZD genomes. It allows identification of affected genes including relevant network and pathways that may account for the diseased state in pair specific patient.

Results

We found multiple twin specific sequence differences between co-twins that included small nucleotides [single nucleotide variants (SNV), small indels and block substitutions], copy number variations (CNVs) and structural variations. The genes affected by these changes belonged to a number of canonical pathways, the most prominent ones are implicated in schizophrenia and related disorders. Although these changes were found in both twins, they were more frequent in the affected twin in both pairs. Two specific pathway defects, glutamate receptor signaling and dopamine feedback in cAMP signaling pathways, were uniquely affected in the two patients representing two unrelated families.

Conclusions

We have identified genome-wide post zygotic mutations in two MZD pairs affected with schizophrenia. It has allowed us to use the threshold model and propose the most likely cause of this disease in the two patients studied. The results support the proposition that each schizophrenia patient may be unique and heterogeneous somatic de novo events may contribute to schizophrenia threshold and discordance of the disease in monozygotic twins.

Electronic supplementary material

The online version of this article (10.1186/s40169-017-0174-1) contains supplementary material, which is available to authorized users.

Possible role of rare variants in Trace amine associated receptor 1 in schizophrenia

Schizophrenia (SZ) is a chronic mental illness with behavioral abnormalities. Recent common variant based genome wide association studies and rare variant detection using next generation sequencing approaches have identified numerous variants that confer risk for SZ, but etiology remains unclear propelling continuing investigations. Using whole exome sequencing, we identified a rare heterozygous variant (c.545G>T; p.Cys182Phe) in Trace amine associated receptor 1 gene (TAAR1 6q23.2) in three affected members in a small SZ family. The variant predicted to be damaging by 15 prediction tools, causes breakage of a conserved disulfide bond in this G-protein-coupled receptor. On screening this intronless gene for additional variant(s) in ~800 sporadic SZ patients, we identified six rare protein altering variants (MAF<0.001) namely p.Ser47Cys, p.Phe51Leu, p.Tyr294Ter, p.Leu295Ser in four unrelated north Indian cases (n=475); p.Ala109Thr and p.Val250Ala in two independent Caucasian/African-American patients (n=310). Five of these variants were also predicted to be damaging. Besides, a rare synonymous variant was observed in SZ patients. These rare variants were absent in north Indian healthy controls (n=410) but significantly enriched in patients (p=0.036). Conversely, three common coding SNPs (rs8192621, rs8192620 and rs8192619) and a promoter SNP (rs60266355) tested for association with SZ in the north Indian cohort were not significant (P>0.05). TAAR1 is a modulator of monoaminergic pathways and interacts with AKT signaling pathways. Substantial animal model based pharmacological and functional data implying its relevance in SZ are also available. However, this is the first report suggestive of the likely contribution of rare variants in this gene to SZ.

Cannabidiol Counteracts Amphetamine-Induced Neuronal and Behavioral Sensitization of the Mesolimbic Dopamine Pathway through a Novel mTOR/p70S6 Kinase Signaling Pathway

Schizophrenia-related psychosis is associated with disturbances in mesolimbic dopamine (DA) transmission, characterized by hyperdopaminergic activity in the mesolimbic pathway. Currently, the only clinically effective treatment for schizophrenia involves the use of antipsychotic medications that block DA receptor transmission. However, these medications produce serious side effects leading to poor compliance and treatment outcomes. Emerging evidence points to the involvement of a specific phytochemical component of marijuana called cannabidiol (CBD), which possesses promising therapeutic properties for the treatment of schizophrenia-related psychoses. However, the neuronal and molecular mechanisms through which CBD may exert these effects are entirely unknown. We used amphetamine (AMPH)-induced sensitization and sensorimotor gating in rats, two preclinical procedures relevant to schizophrenia-related psychopathology, combined with in vivo single-unit neuronal electrophysiology recordings in the ventral tegmental area, and molecular analyses to characterize the actions of CBD directly in the nucleus accumbens shell (NASh), a brain region that is the current target of most effective antipsychotics. We demonstrate that Intra-NASh CBD attenuates AMPH-induced sensitization, both in terms of DAergic neuronal activity measured in the ventral tegmental area and psychotomimetic behavioral analyses. We further report that CBD controls downstream phosphorylation of the mTOR/p70S6 kinase signaling pathways directly within the NASh. Our findings demonstrate a novel mechanism for the putative antipsychotic-like properties of CBD in the mesolimbic circuitry. We identify the molecular signaling pathways through which CBD may functionally reduce schizophrenia-like neuropsychopathology.

SIGNIFICANCE STATEMENT

The cannabis-derived phytochemical, cannabidiol (CBD), has been shown to have pharmacotherapeutic efficacy for the treatment of schizophrenia. However, the mechanisms by which CBD may produce antipsychotic effects are entirely unknown. Using preclinical behavioral procedures combined with molecular analyses and in vivo neuronal electrophysiology, our findings identify a functional role for the nucleus accumbens as a critical brain region whereby CBD can produce effects similar to antipsychotic medications by triggering molecular signaling pathways associated with the effects of classic antipsychotic medications. Specifically, we report that CBD can attenuate both behavioral and dopaminergic neuronal correlates of mesolimbic dopaminergic sensitization, via a direct interaction with mTOR/p70S6 kinase signaling within the mesolimbic pathway.

New Concepts in Dopamine D2 Receptor Biased Signaling and Implications for Schizophrenia Therapy

The dopamine D₂ receptor (D₂R) is a G protein-coupled receptor that is a common target for antipsychotic drugs. Antagonism of D₂R signaling in the striatum is thought to be the primary mode of action of antipsychotic drugs in alleviating psychotic symptoms. However, antipsychotic drugs are not clinically effective at reversing cortical-related symptoms, such as cognitive deficits in schizophrenia. While the exact mechanistic underpinnings of these cognitive deficits are largely unknown, deficits in cortical dopamine function likely play a contributing role. It is now recognized that similar to most G protein-coupled receptors, D₂Rs signal not only through canonical G protein pathways but also through noncanonical beta-arrestin2-dependent pathways. We review the current mechanistic bases for this dual signaling mode of D₂Rs and how these new concepts might be leveraged for therapeutic gain to target both cortical and striatal dysfunction in dopamine neurotransmission and hence have the potential to correct both positive and cognitive symptoms of schizophrenia.

Novel Dopamine Therapeutics for Cognitive Deficits in Schizophrenia

Schizophrenia is characterized by profound cognitive deficits that are not alleviated by currently available medications. Many of these cognitive deficits involve dysfunction of the newly evolved, dorsolateral prefrontal cortex (dlPFC). The brains of patients with schizophrenia show evidence of dlPFC pyramidal cell dendritic atrophy, likely reductions in cortical dopamine, and possible changes in dopamine D1 receptors (D1R). It has been appreciated for decades that optimal levels of dopamine are essential for dlPFC working memory function, with many beneficial actions arising from D1R stimulation. D1R are concentrated on dendritic spines in the primate dlPFC, where their stimulation produces an inverted-U dose response on dlPFC neuronal firing and cognitive performance during working memory tasks. Research in both academia and the pharmaceutical industry has led to the development of selective D1 agonists, e.g., the first full D1 agonist, dihydrexidine, which at low doses improved working memory in monkeys. Dihydrexidine has begun to be tested in patients with schizophrenia or schizotypal disorder. Initial results are encouraging, but studies are limited by the pharmacokinetics of the drug. These data, however, have spurred efforts toward the discovery and development of improved or novel new compounds, including D1 agonists with better pharmacokinetics, functionally selective D1 ligands, and D1R positive allosteric modulators. One or several of these approaches should allow optimization of the beneficial effects of D1R stimulation in the dlPFC that can be translated into clinical practice.

Distinct cortical and striatal actions of a β-arrestin-biased dopamine D2 receptor ligand reveal unique antipsychotic-like properties

The current dopamine (DA) hypothesis of schizophrenia postulates striatal hyperdopaminergia and cortical hypodopaminergia. Although partial agonists at DA D2 receptors (D2Rs), like aripiprazole, were developed to simultaneously target both phenomena, they do not effectively improve cortical dysfunction. In this study, we investigate the potential for newly developed β-arrestin2 (βarr2)-biased D2R partial agonists to simultaneously target hyper- and hypodopaminergia. Using neuron-specific βarr2-KO mice, we show that the antipsychotic-like effects of a βarr2-biased D2R ligand are driven through both striatal antagonism and cortical agonism of D2R-βarr2 signaling. Furthermore, βarr2-biased D2R agonism enhances firing of cortical fast-spiking interneurons. This enhanced cortical agonism of the biased ligand can be attributed to a lack of G-protein signaling and elevated expression of βarr2 and G protein-coupled receptor (GPCR) kinase 2 in the cortex versus the striatum. Therefore, we propose that βarr2-biased D2R ligands that exert region-selective actions could provide a path to develop more effective antipsychotic therapies.

Use of the Clinical Laboratory in Psychiatric Practice

In this review, the authors address the general principles of prescribing psychiatric medications and discuss how the clinical laboratory can be used to guide prescribing practices. Treatment considerations in different settings and for different medications are discussed. Because the clinical laboratory is advancing in its technology, so should the clinician's knowledge of how to use the clinical laboratory. The authors propose recommendations and a simple algorithm for how to use medication levels in blood and other fluids to guide care in medications without well-defined therapeutic windows.

COMT val158met moderation of dopaminergic drug effects on cognitive function: a critical review

The relationship between dopamine (DA) tone in the prefrontal cortex (PFC) and PFC-dependent cognitive functions (for example, working memory, selective attention, executive function) may be described by an inverted-U-shaped function, in which both excessively high and low DA is associated with impairment. In the PFC, the COMT val158met single nucleotide polymorphism (rs4680) confers differences in catechol-O-methyltransferase (COMT) efficacy and DA tone, and individuals homozygous for the val allele display significantly reduced cortical DA. Many studies have investigated whether val158met genotype moderates the effects of dopaminergic drugs on PFC-dependent cognitive functions. A review of 25 such studies suggests evidence for this pharmacogenetic effect is mixed for stimulants and COMT inhibitors, which have greater effects on D1 receptors, and strong for antipsychotics, which have greater effects on D2 receptors. Overall, COMT val158met genotype represents an enticing target for identifying individuals who are more likely to respond positively to dopaminergic drugs.

Maternal deprivation disrupts mitochondrial energy homeostasis in the brain of rats subjected to ketamine-induced schizophrenia

Maternal deprivation (MD) appears to be one of the environmental factors involved in the pathophysiology of schizophrenia. A widely used animal model of the schizophrenia involves the administration of ketamine, a dissociative anesthetic, NMDA receptors noncompetitive antagonist, that induce symptoms such as schizophrenia. To clarify the molecular mechanism of schizophrenia induced by MD, we investigated alterations in energetic metabolism, oxidative stress and neurotrophic factor levels in the brain of rats following MD and/or a single administration of ketamine during adulthood. Male Wistar rats were subjected to MD for 10 days. Additionally, these animals received acute ketamine (5, 15 or 25 mg/kg by intraperitoneal route, i.p.) during adulthood, and 30 min later, they were killed and the prefrontal cortex (PFC), the hippocampus and the striatum were removed for molecular analyses. Ketamine 25 mg/kg and/or MD and Ketamine 15 and 5 mg/kg with MD decreased the creatine kinase (CK) activity in the hippocampus. The enzyme activity of succinate dehydrogenase (SDH) in the Krebs cycle had increased in the striatum following the administration of ketamine 25 mg/kg, MD per se or MD plus ketamine 5 and 15 mg/kg. MD per se or MD combined with ketamine in different doses increased the activity of mitochondrial complexes. The PFC of animals subjected to MD and administered with ketamine 5 mg/kg exhibited increased protein carbonyl content. In the hippocampus, ketamine 15 mg/kg, ketamine 25 mg/kg and MD each increased the carbonyl content. In the striatum, the TBARS levels were increased by the administration of ketamine 25 mg/kg. Finally, in the hippocampus, MD alone or in combination with ketamine reduced the Nerve Growth Factor (NGF) levels; however, the Brain-derived Neurotrophic Factor (BDNF) levels were unaltered. In the present study, we suggest that MD increased the risk of psychotic symptoms in adulthood, altering different parameters of energy and oxidative stress. Our results suggest that adverse experiences occurring early in life may sensitize specific neurocircuits to subsequent stressors, inducing vulnerability, and may help us understand the pathophysiological mechanisms involved in this disorder.

The PDE10A inhibitor MP-10 and haloperidol produce distinct gene expression profiles in the striatum and influence cataleptic behavior in rodents

Phosphodiesterase 10A (PDE10A) has garnered attention as a potential therapeutic target for schizophrenia due to its prominent striatal expression and ability to modulate striatal signaling. The present study used the selective PDE10A inhibitor MP-10 and the dopamine D2 antagonist haloperidol to compare effects of PDE10A inhibition and dopamine D2 blockade on striatopallidal (D2) and striatonigral (D1) pathway activation. Our studies confirmed that administration of MP-10 significantly elevates expression of the immediate early genes (IEG) c-fos, egr-1, and arc in rat striatum. Furthermore, we demonstrated that MP-10 induced egr-1 expression was distributed evenly between enkephalin-containing D2-neurons and substance P-containing D1-neurons. In contrast, haloperidol (3 mg/kg) selectively activated egr-1 expression in enkephalin neurons. Co-administration of MP-10 and haloperidol (0.5 mg/kg) increased IEG expression to a greater extent than either compound alone. Similarly, in a rat catalepsy assay, administration of haloperidol (0.5 mg/kg) or MP-10 (3-30 mg/kg) did not produce cataleptic behavior when dosed alone, but co-administration of haloperidol with MP-10 (3 and 10 mg/kg) induced cataleptic behaviors. Interestingly, co-administration of haloperidol with a high dose of MP-10 (30 mg/kg) failed to produce cataleptic behavior. These findings are important for understanding the neural circuits involved in catalepsy and suggest that the behavioral effects produced by PDE10A inhibitors may be influenced by concomitant medication and the level of PDE10A inhibition achieved by the dose of the inhibitor.

A systematic microdialysis study of dopamine transmission in the accumbens shell/core and prefrontal cortex after acute antipsychotics

RATIONALE

The only systematic in vivo studies comparing antipsychotic (AP) effects on nucleus accumbens (NAc) shell and core dopamine (DA) transmission are voltammetric studies performed in pargyline-pretreated, halothane-anaesthetized rats. Studies in freely moving rats not pretreated with pargyline are not available. This study was intended to fill this gap by the use of in vivo microdialysis in freely moving rats.

METHODS

Male Sprague-Dawley rats were implanted with microdialysis probes in the NAc shell and core and medial prefrontal cortex (PFCX). The next day, rats were administered intravenously with two or three doses of APs, and dialysate DA was monitored in 10-min samples. Some rats were pretreated with pargyline (75 mg/kg i.p.) and after 1 h were given clozapine or risperidone.

RESULTS

Clozapine, risperidone, quetiapine, raclopride, sulpiride and amisulpride increased DA preferentially in the NAc shell. Such preferential effect on shell DA was not observed after haloperidol, chlorpromazine and olanzapine. In contrast to voltammetric studies, a preferential effect on NAc core DA was not observed after any dose of AP. Pargyline pretreatment did not reduce but actually amplified the preferential effect of clozapine and risperidone on NAc shell DA.

CONCLUSIONS

Apart from raclopride and olanzapine, the APs with lower extrapyramidal effects could be distinguished from typical APs on the basis of their ability to preferentially stimulate DA transmission in the NAc shell. There was no relationship between stimulation of PFCX DA and atypical APs profile. The differences between this study and voltammetry studies were not attributable to pargyline pretreatment.

Effect of sepsis on behavioral changes on the ketamine-induced animal model of schizophrenia

This study aimed to evaluate the effect of sepsis on behavioral changes on the ketamine-induced animal model of schizophrenia. Male Wistar rats underwent Cecal Ligation and Perporation (CLP) with "basic support" or were sham-operated. After 30 days, the animals were submitted to a model of schizophrenia by injection of Ketamine. The behavior tests were performed after 30 min of the injection of Ketamine or saline. Ketamine in doses of 15 and 25mg/kg increased locomotor activity, latency to first contact in the social interaction and stereotyped behavior. Some changes caused by sepsis may be associated with a predisposition to develop schizophrenia in the animal model.

Divergent effects of first-generation and second-generation antipsychotics on cortical thickness in first-episode psychosis

BACKGROUND

Whether there are differential effects of first-generation antipsychotics (FGAs) and second-generation antipsychotics (SGAs) on the brain is currently debated. Although some studies report that FGAs reduce grey matter more than SGAs, others do not, and research to date is limited by a focus on schizophrenia spectrum disorders. To address this limitation, this study investigated the effects of medication in patients being treated for first-episode schizophrenia or affective psychoses.

METHOD

Cortical thickness was compared between 52 first-episode psychosis patients separated into diagnostic (i.e. schizophrenia or affective psychosis) and medication (i.e. FGA and SGA) subgroups. Patients in each group were also compared to age- and sex-matched healthy controls (n = 28). A whole-brain cortical thickness interaction analysis of medication and diagnosis was then performed. Correlations between cortical thickness with antipsychotic dose and psychotic symptoms were examined.

RESULTS

The effects of medication and diagnosis did not interact, suggesting independent effects. Compared with controls, diagnostic differences were found in frontal, parietal and temporal regions. Decreased thickness in FGA-treated versus SGA-treated groups was found in a large frontoparietal region (p < 0.001, corrected). Comparisons with healthy controls revealed decreased cortical thickness in the FGA group whereas the SGA group showed increases in addition to decreases. In FGA-treated patients cortical thinning was associated with higher negative symptoms whereas increased cortical thickness in the SGA-treated group was associated with lower positive symptoms.

CONCLUSIONS

Our results suggest that FGA and SGA treatments have divergent effects on cortical thickness during the first episode of psychosis that are independent from changes due to illness.

The concomitant use of second-generation antipsychotics and long-term antiretroviral therapy may be associated with increased cardiovascular risk

To study the effect of concurrent use of second-generation antipsychotics (SGAs) on metabolic syndrome (MetS) components conferring increased cardiovascular risk in a sample of human immunodeficiency virus (HIV)-infected adults taking antiretroviral therapy (ART). A retrospective study of participants consecutively recruited at the UCSD HIV Neurobehavioral Research Program examined effects of combined ART and SGAs on body mass index (BMI), nonfasting serum lipids, diabetes mellitus (DM) incidence, and mean arterial pressure (MAP). Metabolic outcome variables and covariates were compared using t-tests, Chi-squared or Fisher's exact tests. Linear and logistic multivariable models explored metabolic outcomes for participants taking (SGA+) or not taking (SGA-) concomitant SGAs, after controlling for demographic and HIV disease- and ART-related covariates. Of 2229 HIV-infected participants, 12% (N=258) were treated with SGAs. In multivariable models adjusted for relevant covariates, the SGA+ group had significantly higher mean triglycerides, significantly higher odds of DM, significantly higher MAPs and marginally higher BMI. The use of SGAs in HIV-infected adults taking ART was independently associated with worse indicators of MetS and cardiovascular risk. Aggressive monitoring for the metabolic complications from concurrent SGA and ART is indicated in all patients receiving these medication combinations.

New approaches to the management of schizophrenia: focus on aberrant hippocampal drive of dopamine pathways

Schizophrenia is a disease affecting up to 1% of the population. Current therapies are based on the efficacy of chlorpromazine, discovered over 50 years ago. These drugs block dopamine D2-like receptors and are effective at primarily treating positive symptoms in a subset of patients. Unfortunately, current therapies are far from adequate, and novel treatments require a better understanding of disease pathophysiology. Here we review the dopamine, gamma-aminobutyric acid (GABA), and glutamate hypotheses of schizophrenia and describe a pathway whereby a loss of inhibitory signaling in ventral regions of the hippocampus actually drives a dopamine hyperfunction. Moreover, we discuss novel therapeutic approaches aimed at attenuating ventral hippocampal activity in a preclinical model of schizophrenia, namely the MAM GD17 rat. Specifically, pharmacological (allosteric modulators of the α5 GABAA receptor), neurosurgical (deep brain stimulation), and cell-based (GABAergic precursor transplants) therapies are discussed. By better understanding the underlying circuit level dysfunctions in schizophrenia, novel treatments can be advanced that may provide better efficacy and a superior side effect profile to conventional antipsychotic medications.

Response inhibition and interference control in obsessive-compulsive spectrum disorders

Over the past 20 years, motor response inhibition and interference control have received considerable scientific effort and attention, due to their important role in behavior and the development of neuropsychiatric disorders. Results of neuroimaging studies indicate that motor response inhibition and interference control are dependent on cortical–striatal–thalamic–cortical (CSTC) circuits. Structural and functional abnormalities within the CSTC circuits have been reported for many neuropsychiatric disorders, including obsessive–compulsive disorder (OCD) and related disorders, such as attention-deficit hyperactivity disorder, Tourette’s syndrome, and trichotillomania. These disorders also share impairments in motor response inhibition and interference control, which may underlie some of their behavioral and cognitive symptoms. Results of task-related neuroimaging studies on inhibitory functions in these disorders show that impaired task performance is related to altered recruitment of the CSTC circuits. Previous research has shown that inhibitory performance is dependent upon dopamine, noradrenaline, and serotonin signaling, neurotransmitters that have been implicated in the pathophysiology of these disorders. In this narrative review, we discuss the common and disorder-specific pathophysiological mechanisms of inhibition-related dysfunction in OCD and related disorders.

MicroRNA-9 and microRNA-326 regulate human dopamine D2 receptor expression, and the microRNA-mediated expression regulation is altered by a genetic variant

The human dopamine receptor D2 (DRD2) has been implicated in the pathophysiology of schizophrenia and other neuropsychiatric disorders. Most antipsychotic drugs influence dopaminergic transmission through blocking dopamine receptors, primarily DRD2. We report here the post-transcriptional regulation of DRD2 expression by two brain-expressed microRNAs (miRs), miR-326 and miR-9, in an ex vivo mode, and show the relevance of miR-mediated DRD2 expression regulation in human dopaminergic neurons and in developing human brains. Both miRs targeted the 3'-UTR (untranslated region) of DRD2 in NT2 (neuron-committed teratocarcinoma, which endogenously expresses DRD2) and CHO (Chinese hamster ovary) cell lines, decreasing luciferase activity measured by a luciferase reporter gene assay. miR-326 overexpression reduced DRD2 mRNA and DRD2 receptor synthesis. Both antisense miR-326 and antisense miR-9 increased DRD2 protein abundance, suggesting an endogenous repression of DRD2 expression by both miRs. Furthermore, a genetic variant (rs1130354) within the DRD2 3'-UTR miR-targeting site interferes with miR-326-mediated repression of DRD2 expression. Finally, co-expression analysis identified an inverse correlation of DRD2 expression with both miR-326 and miR-9 in differentiating dopaminergic neurons derived from human induced pluripotent stem cells (iPSCs) and in developing human brain regions implicated in schizophrenia. Our study provides empirical evidence suggesting that miR-326 and miR-9 may regulate dopaminergic signaling, and miR-326 and miR-9 may be considered as potential drug targets for the treatment of disorders involving abnormal DRD2 function, such as schizophrenia.

Restricted access to standard or high fat chow alters sensitivity of rats to the 5-HT(2A/2C) receptor agonist 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane

Feeding conditions can impact sensitivity to drugs acting on dopamine receptors; less is known about the impact of feeding conditions on the effects of drugs acting on serotonin (5-HT) receptors. This study examined the effects of feeding conditions on sensitivity to the direct-acting 5-HT(2A/2C) receptor agonist 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM; 0.1-3.2 mg/kg) and the direct-acting dopamine D3/D2 receptor agonist quinpirole (0.0032-0.32 mg/kg). Male Sprague-Dawley rats had free access (11 weeks), followed by restricted access (6 weeks), to high fat (34.3%, n=8) or standard (5.7% fat; n=7) chow. Rats eating high fat chow became insulin resistant and gained more weight than rats eating standard chow. Free access to high fat chow did not alter sensitivity to DOM-induced head twitch but increased sensitivity to quinpirole-induced yawning. Restricting access to high fat or standard chow shifted the DOM-induced head twitch dose-response curve to the right and shifted the quinpirole-induced yawning dose-response curve downward in both groups of rats. Some drugs of abuse and many therapeutic drugs act on 5-HT and dopamine systems; these results show that feeding conditions impact sensitivity to drugs acting on these systems, thereby possibly affecting vulnerability to abuse, as well as the therapeutic effectiveness of drugs.

The role of dopamine in schizophrenia from a neurobiological and evolutionary perspective: old fashioned, but still in vogue

Dopamine is an inhibitory neurotransmitter involved in the pathology of schizophrenia. The revised dopamine hypothesis states that dopamine abnormalities in the mesolimbic and prefrontal brain regions exist in schizophrenia. However, recent research has indicated that glutamate, GABA, acetylcholine, and serotonin alterations are also involved in the pathology of schizophrenia. This review provides an in-depth analysis of dopamine in animal models of schizophrenia and also focuses on dopamine and cognition. Furthermore, this review provides not only an overview of dopamine receptors and the antipsychotic effects of treatments targeting them but also an outline of dopamine and its interaction with other neurochemical models of schizophrenia. The roles of dopamine in the evolution of the human brain and human mental abilities, which are affected in schizophrenia patients, are also discussed.

Integrated approaches to understanding antipsychotic drug action at GPCRs

The G-protein coupled receptor (GPCR) family of genes represents one of the largest druggable families of genes in the human genome. This is evident by the fact that approximately 30% of currently marketed drugs target GPCRs. However, many of these drugs are limited in their clinical potential as they are associated with debilitating side effects-a consequence of our incomplete understanding of their pharmacology and the signaling pathways regulated by GPCRs. Because of the limited range of tools available to resolve these issues, integrated approaches are required to fully understand the pharmacological action of drugs and the biochemical repertoire regulated by GPCRs. In this review we will focus on the action of antipsychotic drugs on certain monoamine GPCRs in the central nervous system (CNS) and the approaches being developed to elucidate their distinct pharmacology.

Quetiapine and flupentixol differentially improve anterior cingulate cortex function in schizophrenia patients: an event-related potential study

Atypical antipsychotic agents are a frequently and effectively used treatment in schizophrenia and psychotic disorders. Other than conventional antipsychotics, which mainly exert their pharmacological effect in subcortical dopaminergic systems, atypical antipsychotics additionally affect partly serotonergically innervated structures within prefrontal areas, such as the anterior cingulate cortex (ACC). However, only few controlled, randomized studies have so far investigated direct and indirect effects of atypical antipsychotics on the ACC and, up until now, no clinical investigation has exclusively addressed the specific effects of quetiapine on ACC function. The present study assessed ACC function in 18 quetiapine-medicated patients and 13 flupentixol-treated patients suffering from schizophrenia by means of the error-related negativity (ERN), a neurophysiological marker of ACC function, in a pre-post design. Between-group comparisons revealed different effects of quetiapine and flupentixol on ACC function despite similar improvement in psychopathology, cognitive performance and quality of life. Whereas atypical treatment was associated with an increase in amplitudes over time, there were prolonged ERN peak latencies in patients treated with the typical agent. Moreover, treatment effects depended on baseline prefrontal cortex function in both groups. We conclude that both flupentixol and quetiapine improve prefrontal function especially in patients with weak initial ACC function which might be due to their shared affinity for serotonin receptors in frontal brain regions. However, since this affinity is more pronounced for quetiapine, patients treated with quetiapine seemed to profit more evidently concerning their prefrontal cortex function compared to patients of the flupentixol group, who exhibited a compensatory prolongation of processes.

Effect of maternal deprivation on acetylcholinesterase activity and behavioral changes on the ketamine-induced animal model of schizophrenia

Maternal deprivation has been associated with physiological and developmental changes that may be related to an increased risk for childhood and adult neuropsychiatric diseases. A growing number of studies demonstrated the importance of childhood experiences in the development of psychosis and schizophrenia in adulthood. Therefore, the present study investigated different behavior responses in rats following maternal deprivation and/or ketamine treatment in adulthood. Male rats were subjected to maternal deprivation for 180 min from postnatal day-01 to postnatal day-10. We evaluated locomotor activity, avoidance task and social interaction of adult male rats deprived or not deprived that were administered with saline or acute subanesthetic doses of ketamine (5, 15 and 25 mg/kg, i.p.). Our results show that only ketamine (25 mg/kg, i.p.) treatment in the adult rats lead to hyperlocomotion but not ketamine (5 and 15 mg/kg) and maternal deprivation alone. However, maternally deprived rats treated with ketamine (5 mg/kg) induced hyperlocomotion. Additionally, ketamine (25 mg/kg) and maternal deprivation alone induced cognitive deficit in the avoidance task. Rats deprived of and treated with ketamine (5, 15 and 25 mg/kg) also lead to memory deficit. Moreover, ketamine (25 mg/kg) and maternal deprivation alone increased latency to start social behavior. However, ketamine (5 mg/kg) and maternal deprivation lead to an increase of latency to start social behavior. Biochemistry data showed that all doses of ketamine and ketamine plus maternal deprivation increased the acetylcholinesterase (AChE) activity in the prefrontal cortex, hippocampus and striatum. The major doses of ketamine associated with maternal deprivation induced a major increase of AChE activity. Together, our results suggest that animals subjected to maternal deprivation had an increased risk for schizophrenia-like behavior and cholinergic alteration.

A new perspective for schizophrenia: TAAR1 agonists reveal antipsychotic- and antidepressant-like activity, improve cognition and control body weight

Schizophrenia is a chronic, severe and highly complex mental illness. Current treatments manage the positive symptoms, yet have minimal effects on the negative and cognitive symptoms, two prominent features of the disease with critical impact on the long-term morbidity. In addition, antipsychotic treatments trigger serious side effects that precipitate treatment discontinuation. Here, we show that activation of the trace amine-associated receptor 1 (TAAR1), a modulator of monoaminergic neurotransmission, represents a novel therapeutic option. In rodents, activation of TAAR1 by two novel and pharmacologically distinct compounds, the full agonist RO5256390 and the partial agonist RO5263397, blocks psychostimulant-induced hyperactivity and produces a brain activation pattern reminiscent of the antipsychotic drug olanzapine, suggesting antipsychotic-like properties. TAAR1 agonists do not induce catalepsy or weight gain; RO5263397 even reduced haloperidol-induced catalepsy and prevented olanzapine from increasing body weight and fat accumulation. Finally, TAAR1 activation promotes vigilance in rats and shows pro-cognitive and antidepressant-like properties in rodent and primate models. These data suggest that TAAR1 agonists may provide a novel and differentiated treatment of schizophrenia as compared with current medication standards: TAAR1 agonists may improve not only the positive symptoms but also the negative symptoms and cognitive deficits, without causing adverse effects such as motor impairments or weight gain.

The influence of glutamatergic antagonism on motor variability, and comparison to findings in schizophrenia patients

OBJECTIVE

The primary aim of this explorative study was to investigate the influence of the glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist memantine on motor activity in healthy subjects. Secondarily, we wanted to compare these data to findings in a sample of schizophrenia patients.

METHODS

The healthy subjects acted as their own controls in an open-within-subject design. Motor activity was recorded with an actigraph worn for 24 h in the drug-free, and steady-state memantine conditions, respectively. Motor activity levels for 1-min intervals were analysed by means of both linear and nonlinear methods. The schizophrenia patients were monitored only once, without memantine manipulation.

RESULTS

The root mean square successive differences (RMSSD) and the RMSSD/SD ratio were increased by memantine, and memantine was also associated with lower autocorrelation (lag 1) but in recordings from the right arm only. These movement patterns partly corresponded to those found in a sample of drug-treated schizophrenia patients. Total activity level, standard deviation (SD) and sample entropy were not significantly different in the memantine versus drug-free condition.

CONCLUSION

The findings suggest a role for the NMDA receptor in the regulation of motor activity in healthy individuals as memantine increased the variability in the motor recordings and the alterations between adjacent motor recordings. It is suggested that the findings may be relevant to the role played by glutamate and the NMDA receptor functioning to the motor disturbances in schizophrenia.

Quality of life and adverse effects of olanzapine versus risperidone therapy in patients with schizophrenia

This cross-sectional study aimed to compare the effects of treatment with an atypical antipsychotic drug (olanzapine or risperidone) on quality of life (QoL) and to document adverse effects in 115 patients diagnosed with schizophrenia who attended the ambulatory service of Hospital Dr. João Machado, Natal, Rio Grande do Norte, Brazil. Socioeconomic, sociodemographic, and clinical variables were compared. The QoL Scale validated for Brazil (QLS-BR) was used to evaluate QoL, and adverse effects were assessed using the Udvalg for Kliniske Undersøgelser Side Effect Rating Scale. Data were analyzed using the χ(2) test and Student's t test, with a significance level of 5 %. Patients in both drug groups showed severe impairment in the occupational domain of the QLS-BR. Global QLS-BR scores indicated impairment among risperidone users and severe impairment among olanzapine users. The most significant side effects were associated with risperidone, including asthenia/lassitude/fatigue, somnolence/sedation, paresthesia, change in visual accommodation, increased salivation, diarrhea, orthostatic posture, palpitations/tachycardia, erythema, photosensitivity, weight loss, galactorrhea, decreased sexual desire, erectile/orgasmic dysfunction, vaginal dryness, headache, and physical dependence. QoL was impaired in patients using olanzapine and in those using risperidone. Risperidone use was associated with psychic, neurological, and autonomous adverse effects and other side effects.