GWAS quality score for evaluating associated regions in GWAS analyses.

MOTIVATION: The number of significantly associated regions reported in genome-wide association studies (GWAS) for polygenic traits typically increases with sample size. A traditional tool for quality control and identification of significant regions has been a visual inspection of how significant and correlated genetic variants cluster within a region. However, while inspecting hundreds of regions, this subjective method can misattribute significance to some loci or neglect others that are significant. RESULTS: The GWAS quality score (GQS) identifies suspicious regions and prevents erroneous interpretations with an objective, quantitative and automated method. The GQS assesses all measured single nucleotide polymorphisms (SNPs) that are linked by inheritance to each other [linkage disequilibrium (LD)] and compares the significance of trait association of each SNP to its LD value for the reported index SNP. A GQS value of 1.0 ascribes a high level of confidence to the entire region and its underlying gene(s), while GQS values <1.0 indicate the need to closely inspect the outliers. We applied the GQS to published and non-published genome-wide summary statistics and report suspicious regions requiring secondary inspection while supporting the majority of reported regions from large-scale published meta-analyses. AVAILABILITY AND IMPLEMENTATION: The GQS code/scripts can be cloned from GitHub (https://github.com/Xswapnil/GQS/). The analyst can use whole-genome summary statistics to estimate GQS for each defined region. We also provide an online tool (http://35.227.18.38/) that gives access to the GQS. The quantitative measure of quality attributes by GQS and its visualization is an objective method that enhances the confidence of each genomic hit. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Clinical validity of cytochrome P450 metabolism and serotonin gene variants in psychiatric pharmacotherapy.

Adverse events, response failures and medication non-compliance are common in patients receiving medications for the treatment of mental illnesses. A systematic literature review assessed whether pharmacokinetic (PK) or pharmacodynamic (PD) responses to 26 commonly prescribed antipsychotic and antidepressant medications, including efficacy or side effects, are associated with nucleotide polymorphisms in eight commonly studied genes in psychiatric pharmacotherapy: CYP2D6, CYP2C19, CYP2C9, CYP1A2, CYP3A4, HTR2C, HTR2A, and SLC6A4. Of the 294 publications included in this review, 168 (57%) showed significant associations between gene variants and PK or PD outcomes. Other studies that showed no association often had insufficient control for confounding variables, such as co-medication use, or analysis of medications not substrates of the target gene. The strongest gene-outcome associations were for the PK profiles of CYP2C19 and CYP2D6 (93% and 90%, respectively), for the PD associations between HTR2C and weight gain (57%), and for SLC6A4 and clinical response (54%), with stronger SLC6A4 response associations for specific drug classes (60-83%). The preponderance of evidence supports the validity of analyzing nucleotide polymorphisms in CYP and pharmacodynamic genes to predict the metabolism, safety, or therapeutic efficacy of psychotropic medications commonly used for the treatment of depression, schizophrenia, and bipolar illness.

Clinical utility of combinatorial pharmacogenomic testing in depression: A Canadian patient- and rater-blinded, randomized, controlled trial.

The pharmacological treatment of depression consists of stages of trial and error, with less than 40% of patients achieving remission during first medication trial. However, in a large, randomized-controlled trial (RCT) in the U.S. ("GUIDED"), significant improvements in response and remission rates were observed in patients who received treatment guided by combinatorial pharmacogenomic testing, compared to treatment-as-usual (TAU). Here we present results from the Canadian "GAPP-MDD" RCT. This 52-week, 3-arm, multi-center, participant- and rater-blinded RCT evaluated clinical outcomes among patients with depression whose treatment was guided by combinatorial pharmacogenomic testing compared to TAU. The primary outcome was symptom improvement (change in 17-item Hamilton Depression Rating Scale, HAM-D17) at week 8. Secondary outcomes included response (≥50% decrease in HAM-D17) and remission (HAM-D17 ≤ 7) at week 8. Numerically, patients in the guided-care arm had greater symptom improvement (27.6% versus 22.7%), response (30.3% versus 22.7%), and remission rates (15.7% versus 8.3%) compared to TAU, although these differences were not statistically significant. Given that the GAPP-MDD trial was ultimately underpowered to detect statistically significant differences in patient outcomes, it was assessed in parallel with the larger GUIDED RCT. We observed that relative improvements in response and remission rates were consistent between the GAPP-MDD (33.0% response, 89.0% remission) and GUIDED (31.0% response, 51.0% remission) trials. Together with GUIDED, the results from the GAPP-MDD trial indicate that combinatorial pharmacogenomic testing can be an effective tool to help guide depression treatment in the context of the Canadian healthcare setting (ClinicalTrials.gov NCT02466477).

Cognition-enhancing properties of Dimebon in a rat novel object recognition task are unlikely to be associated with acetylcholinesterase inhibition or N-methyl-D-aspartate receptor antagonism.

Dimebon (dimebolin) treatment enhances cognition in patients with Alzheimer's disease (AD) or Huntington's disease. Although Dimebon was originally thought to improve cognition and memory through inhibition of acetylcholinesterase (AChE) and the N-methyl-d-aspartate (NMDA) receptor, the low in vitro affinity for these targets suggests that these mechanisms may not contribute to its clinical effects. To test this hypothesis, we assessed whether Dimebon enhances cognition in rats and if such an action is related to either mechanism or additional candidate mechanisms. Acute oral administration of Dimebon to rats (0.05, 0.5, and 5 mg/kg) enhanced cognition in a novel object recognition task and produced Dimebon brain concentrations of 1.7 +/- 0.43, 14 +/- 5.1, and 172 +/- 94 nM, respectively. At these concentrations, Dimebon did not alter the activity of recombinant human or rat brain AChE. Unlike the AChE inhibitors donepezil and galantamine, Dimebon did not change acetylcholine levels in the hippocampus or prefrontal cortex of freely moving rats. Dimebon displays affinity for the NMDA receptor (K(i) = 105 +/- 18 microM) that is considerably higher than brain concentrations associated with cognition enhancement in the novel object recognition task and 200-fold weaker than that of memantine (K(i) = 0.54 +/- 0.05 microM). Dimebon did not block NMDA-induced calcium influx in primary neuronal cells (IC(50) > 50 microM), consistent with a lack of significant effect on this pathway. The cognition-enhancing effects of Dimebon are unlikely to be mediated by AChE inhibition or NMDA receptor antagonism, and its mechanism of action appears to be distinct from currently approved medications for AD.

Active immunotherapy and alternative therapeutic modalities for Alzheimer's disease.

As knowledge of Alzheimer's disease (AD) progression improves, the field has recognized the need to diversify the pipeline, broaden strategies and approaches to therapies, as well as delivery mechanisms. A better understanding of the earliest biological processes of AD/dementia would help inform drug target selection. Currently there are a number of programs exploring these alternate avenues. This meeting will allow experts in the field (academia, industry, government) to provide perspectives and experiences that can help elucidate what the pipeline looks like today and what avenues hold promise in developing new therapies across the stages of AD. The focus here is on Active Immunotherapies and Alternative Therapeutic Modalities. This topic includes active vaccines, antisense oligomers, and cell-based therapy among others, and highlights new clinical developments that utilize these modalities.

Aripiprazole blocks reinstatement of cocaine seeking in an animal model of relapse.

BACKGROUND: Aripiprazole (Abilify) is an atypical antipsychotic drug primarily characterized by partial agonist activity at dopamine (DA) D2 receptors and low side effects. Based on pharmacologic properties that include a stabilization of mesocorticolimbic DA activity, a pathway implicated in addiction, aripiprazole was tested for its ability to prevent relapse to cocaine seeking in rats. METHODS: We assessed the dose-dependent effects of aripiprazole on conditioned cue-induced and cocaine-primed reinstatement of drug-seeking behavior following chronic intravenous cocaine self-administration in an animal model of relapse. RESULTS: Aripiprazole potently and dose-dependently attenuated responding on the previously cocaine-paired lever during both reinstatement conditions, with slightly greater efficacy at reducing conditioned-cued reinstatement. Aripiprazole was effective at doses that failed to alter cocaine self-administration, food self-administration, reinstatement of food-seeking behavior, or basal locomotor activity, suggesting selective effects of aripiprazole on motivated drug-seeking behavior. CONCLUSIONS: These results in a relapse model show that aripiprazole can block cocaine seeking without affecting other behaviors. The D2 partial agonist properties of aripiprazole likely account for the blockade of reinstatement of cocaine-seeking behavior. Given its established efficacy and tolerability as a treatment for psychosis, aripiprazole may be an excellent therapeutic choice for reducing craving and preventing relapse in people with cocaine dependency.

Altered expression of hippocampal dentate granule neuron genes in a mouse model of human 22q11 deletion syndrome.

Hemizygous deletion of a 3 Mb region of 22q11.2 is found in 1/4000 humans and produces 22q11 deletion syndrome (22q11DS). Up to 35% of 22q11DS patients develop schizophrenia, making it the second highest risk factor for schizophrenia. A mouse model for 22q11DS, the Df1/+ mouse, carries a hemizygous deletion in a region syntenic with the human deletion. Df1/+ mice are mostly viable but display deficits in prepulse inhibition and learning and memory, two common traits of schizophrenia thought to result, at least in part, from defects in hippocampal neurons. We used oligonucleotide microarrays and QRT-PCR to evaluate gene expression changes in hippocampal dentate granule neurons of Df1/+ mice versus wild-type littermates (n=12/group). The expression of only 287 genes changed with p value significance below 0.05 by microarray, yet 12 of the 21 Df1 region genes represented on the array showed highly significantly reduced expression compared to wild-type controls (33% on average, p values from 10(-3) to 10(-7)). Variants in two of these genes, COMT and PRODH, have been linked with schizophrenia. Overlap of the 287 genes with the reportedly reduced expression of mitochondrial, ubiquitin/proteasome, and synaptic plasticity genes in schizophrenia dentate granule neurons, was not significant. However, modest increases in expression of mitochondrial electron transport genes were observed in the Df1/+ mice. This perhaps indicates a compensation for mitochondrial dysfunction caused by the strongly reduced expression of the Df1 region-encoded mitochondrial enzymes proline dehydrogenase (Prodh) and thioredoxin reductase 2 (Txnrd2).

Electroconvulsive seizures regulate gene expression of distinct neurotrophic signaling pathways.

Electroconvulsive therapy (ECT) remains the treatment of choice for drug-resistant patients with depressive disorders, yet the mechanism for its efficacy remains unknown. Gene transcription changes were measured in the frontal cortex and hippocampus of rats subjected to sham seizures or to 1 or 10 electroconvulsive seizures (ECS), a model of ECT. Among the 3500-4400 RNA sequences detected in each sample, ECS increased by 1.5- to 11-fold or decreased by at least 34% the expression of 120 unique genes. The hippocampus produced more than three times the number of gene changes seen in the cortex, and many hippocampal gene changes persisted with chronic ECS, unlike in the cortex. Among the 120 genes, 77 have not been reported in previous studies of ECS or seizure responses, and 39 were confirmed among 59 studied by quantitative real time PCR. Another 19 genes, 10 previously unreported, changed by <1.5-fold but with very high significance. Multiple genes were identified within distinct pathways, including the BDNF-MAP kinase-cAMP-cAMP response element-binding protein pathway (15 genes), the arachidonic acid pathway (5 genes), and more than 10 genes in each of the immediate-early gene, neurogenesis, and exercise response gene groups. Neurogenesis, neurite outgrowth, and neuronal plasticity associated with BDNF, glutamate, and cAMP-protein kinase A signaling pathways may mediate the antidepressant effects of ECT in humans. These genes, and others that increase only with chronic ECS such as neuropeptide Y and thyrotropin-releasing hormone, may provide novel ways to select drugs for the treatment of depression and mimic the rapid effectiveness of ECT.

Deficient hippocampal neuron expression of proteasome, ubiquitin, and mitochondrial genes in multiple schizophrenia cohorts.

BACKGROUND: Hippocampal dentate granule neurons are altered in schizophrenia, but it is unknown if their gene expressions change in schizophrenia or other psychiatric diseases. METHODS: Laser-captured dentate granule neurons from two groups of schizophrenia and control cases and from major depression and bipolar disease cases were examined for alterations in gene expression using complementary DNA (cDNA) microarrays and reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Compared with 24 control cases, the 22 schizophrenia patients in both groups revealed decreases in clusters of genes that encode for protein turnover (proteasome subunits and ubiquitin), mitochondrial oxidative energy metabolism (isocitrate, lactate, malate, nicotinamide adenine dinucleotide [NADH], and succinate dehydrogenases; cytochrome C oxidase; adenosine triphosphate [ATP] synthase), and genes associated with neurite outgrowth, cytoskeletal proteins, and synapse plasticity. These changes were not obtained in 9 bipolar cases or 10 major depression cases and were not associated with age, sex, brain weight, body weight, postmortem interval, or drug history. Brain pH contributed to the variance of some genes but was mostly independent of the disease effect. CONCLUSIONS: Decreases in hippocampal neuron gene expression are consistent with brain imaging and microarray studies of the frontal cortex in schizophrenia. A mitochondrial and ubiquitin-proteasome hypofunctioning of dentate granule neurons may contribute to the deficits of schizophrenia.

Clinical Utility of Combinatorial Pharmacogenomics-Guided Antidepressant Therapy: Evidence from Three Clinical Studies.

DNA of 258 patients with treatment-resistant depression was collected in three 8-10 week, two-arm, prospective clinical trials. Forty-four allelic variations were measured in genes for the cytochrome P450 (CYP) enzymes CYP2D6, CYPC19, and CYP1A2, the serotonin transporter (SLC6A4), and the 5-HT2A receptor (HTR2A). The combinatorial pharmacogenomic (CPGx™) GeneSight test results were provided to clinicians to support medication changes from baseline (guided arm), or they were provided at the end of each study to clinicians of unguided patients who were treated as usual (TAU). TAU subjects who at baseline were prescribed medications genetically discordant for them showed only a 12% symptom improvement, far less than the 32.5% or 28.5% improvements of the TAU subjects on yellow-category ('use with caution'; p = 0.002) or green-category medications ('use as recommended'; p = 0.02), respectively. The odds of a clinical response were increased 2.3-fold among all GeneSight-guided compared to all TAU subjects (p = 0.004), and overall, the guided group had a 53% greater improvement in depressive symptoms (p = 0.0002), a 1.7-fold relative improvement in response (p = 0.01), and a number needed to treat for one clinical response above that seen in the TAU group of 6.07.

Combinatorial pharmacogenomic guidance for psychiatric medications reduces overall pharmacy costs in a 1 year prospective evaluation.

OBJECTIVES: The objective of this project was to determine pharmacy cost savings and improvement in adherence based on a combinatorial pharmacogenomic test (CPGx ) in patients who had switched or added a new psychiatric medication after having failed monotherapy for their psychiatric disorder. RESEARCH DESIGN AND METHODS: The prospective project compared 1 year pharmacy claims between a GeneSight CPGx guided cohort and a propensity-matched control group. Patients were project eligible if they augmented or switched to a different antidepressant or antipsychotic medication within the previous 90 days. Following the medication switch or augmentation, pharmacogenomic (PGx) testing was offered to each patient's treating clinician. Pharmacy claims were extracted from the Medco pharmacy claims database for each patient (n = 2168) for 1 year following testing and compared to a 5-to-1 propensity-matched treatment as usual (TAU), standard of care control group (n = 10,880). MAIN OUTCOME MEASURES: Total pharmacy spend per member per year; adherence. RESULTS: Patients who received PGx testing saved $1035.60 in total medication costs (both CNS and non-CNS medications) over 1 year compared to the non-tested standard of care cohort (p = 0.007). PGx testing improved adherence compared to standard of care (ΔPDCCPGx = 0.11 vs ΔPDCTAU = -0.01; p < 0.0001). Pharmacy cost savings averaged $2774.53 for patients who were changed to a CPGx congruent medication regimen, compared to those who were not (p < 0.0001). CONCLUSIONS: PGx testing provides significant 'real world' cost savings, while simultaneously improving adherence in a difficult to treat psychiatric population. Limitations of this study include the lack of therapeutic efficacy follow-up data and possible confounding due to matching only on demographic and psychiatric variables.

Effects of electroconvulsive seizures and antidepressant drugs on brain-derived neurotrophic factor protein in rat brain.

BACKGROUND: The antidepressant-like effects of brain-derived neurotrophic factor (BDNF) infusions in brain, and the upregulation of BDNF mRNA and its receptor in rats exposed to electroconvulsive seizure (ECS) and antidepressants, suggested a role for increased BDNF protein. METHODS: We measured BDNF protein levels with a two-site enzyme-linked immunosorbent assay (ELISA) in six brain regions of adult male rats that received daily ECS or daily injections of antidepressant drugs. RESULTS: The BDNF ELISA method was validated by the 50% loss of BDNF protein in the brains of +/- BDNF knockout mice, the 60%-100% recovery of spiked recombinant BDNF, and by the amounts and regional variations of BDNF measured in the six brain regions. Ten consecutive daily exposures to ECS increased BDNF protein in the parietal cortex (219%), entorhinal cortex (153%), hippocampus (132%), frontal cortex (94%), neostriatum (67%), and septum (29%). BDNF increased gradually in the hippocampus and frontal cortex, with a peak response by the fourth day of ECS. Increases peaked at 15 hours after the last ECS and lasted at least 3 days thereafter. Two weeks of daily injections with the monoamine (MAO)-A and -B inhibitor tranylcypromine (8-10 mg/kg, IP) increased BDNF by 15% in the frontal cortex, and 3 weeks treatment increased it by 18% in the frontal cortex and by 29% in the neostriatum. Tranylcypromine, fluoxetine, and desmethylimipramine did not elevate BDNF in the hippocampus. CONCLUSIONS: Elevations in BDNF protein in brain are consistent with the greater treatment efficacy of ECS and MAO inhibitors in drug-resistant major depressive disorder and may be predictive for the antidepressant action of the more highly efficacious interventions.

Identification of CD40 ligand in Alzheimer's disease and in animal models of Alzheimer's disease and brain injury.

Chronic neuroinflammatory processes including glial activation may play a role in the pathogenesis of Alzheimer's disease (AD). The immune and inflammatory mediator CD40 ligand (CD40L) can augment the activation of cultured microglia by amyloid beta-protein (Abeta) and promote neuron death. We investigated whether CD40L is increased in AD and in animal models of AD and neuroinflammation. In the frontal cortex of elderly, non-AD controls, CD40L immunoreactivity was found in the glial limiting membrane, astrocytes, and vascular profiles in gray and white matter. In AD, intense CD40L immunoreactivity occurred in hypertrophied astrocytes throughout the frontal cortex. The majority of CD40L-immunoreactive astrocytes in the gray matter occurred within, or at the periphery of, Abeta(1-42)-immunoreactive plaques. A semiquantitative analysis revealed a three-fold elevation in the number of CD40L-immunoreactive astrocytes in AD compared to controls. The cortex and hippocampus from 6 and 12 month-old amyloid precursor protein/presenilin 1 transgenic mice exhibited numerous neuritic plaques and CD40L-positive astrocytes, which were not detected in non-transgenic controls. In adult rats, little or no CD40L staining occurred in astrocytes of the intact brain, whereas intrastriatal excitotoxic or stab wound lesions produced a strong CD40L immunoreactivity that was more segregated than glial fibrillary acidic protein. These findings indicate that astrocytes are the predominant source of CD40L in brain, and are consistent with the proposed role of CD40L-mediated neurotoxic inflammation in AD.

Novel directions in antipsychotic target identification using gene arrays.

Schizophrenia is a major health problem that affects 2 million individuals in the United States. Antipsychotics offer considerable symptomatic relief and, although commonly discovered by screening with single biological targets, most interact with multiple receptors and signaling pathways. Considerable evidence from family and twin studies demonstrates genetic components and multiple chromosomal regions associated with schizophrenia. The polygenic nature of schizophrenia and multiple mechanisms for most effective agents indicate the need for broader approaches to target identification. Gene expression profiling of post-mortem human brain tissue simultaneously reveals the expression of many thousands of genes. A comparison of tissue from normals and patients provides a 'disease signature' of aberrantly expressed genes. 'Drug signatures' are the gene expression changes of cultured human or animal neurons treated with psychiatric drugs, and from animals chronically treated with these drugs. A selection of genes from disease and drug signatures can create a set of targets whose changes may better predict disease and its treatment by effective agents. This multi-parameter high throughput screening (MPHTS(SM)) approach evaluates the mRNA expression pattern of cultured cells exposed to candidate compounds. Compounds that normalize genes altered in schizophrenia may better address its underlying causes. Drugs that mimic gene expression changes that are consistently altered by effective antipsychotic agents provide a drug improvement strategy if efficacy is enhanced or side effects are attenuated.

Brain-derived neurotrophic factor is stored in human platelets and released by agonist stimulation.

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays critical roles in the survival, growth, and maintenance of brain and peripheral neurons. We report the presence of BDNF protein in human platelets and its release upon agonist stimulation. The BDNF content of washed platelets varied widely, from 3.5 to 67 ng/4 x 10(8) platelets, averaging 25.2 +/- 21.2 ng/4 x 10(8) platelets (mean+/-SD). The BDNF concentration in platelet-poor plasma was low (1.7+/-1.7 ng/ml, n = 11). Thrombin, collagen, the Ca++ ionophore A23187, and shear stress each induced a rapid release of BDNF from platelets. Up to only half of platelet BDNF was secreted upon agonist stimulation, suggesting that platelets may have a non-releasable pool of BDNF, or that the released BDNF binds to a recognition site on the platelet surface and is internalized, as occurs with serotonin. However, the cognate BDNF receptor, TrkB, was not detected in platelets. Nevertheless, the ability of BDNF to bind washed platelets was shown by FACS analysis confocal microscopy and by the binding and apparent internalization of [125I]-BDNF by platelets. A very high affinity site (Kd = 130 x 10(-15) M, approximately 80 sites/platelet) and a moderately high affinity site (Kd = 20 nM, approximately 3750 sites/platelet) were identified. The BDNF content in two megakaryocytic cell lines, DAMI and Meg-01, was only 0.1% of the content measured in platelets. No BDNF mRNA was detected by Northern blotting in these cell lines or in platelets. The pituitary gland was also ruled out as a source for platelet BDNF, since the BDNF content of rat platelets did not decrease 2 weeks after hypophysectomy. Thus, platelet BDNF is not acquired from the megakaryocyte or pituitary gland, but is probably acquired from other sources via the blood circulation. Platelets appear to bind, store and release BDNF upon activation at the site of traumatic injury to facilitate the repair of peripheral nerves or other tissues that contain TrkB.

Comparison of microarray-based mRNA profiling technologies for identification of psychiatric disease and drug signatures.

The gene expression profiles of human postmortem parietal and prefrontal cortex samples of normal controls and patients with bipolar disease, or human neuroblastoma flat (NBFL) cells treated with the mood-stabilizing drug, valproate, were used to compare the performance of Affymetrix oligonucleotide U133A GeneChips and Agilent Human 1 cDNA microarrays. Among those genes represented on both platforms, the oligo array identified 26-53% more differentially expressed genes compared to the cDNA array in the three experiments, when identical fold change and t-test criteria were applied. The increased sensitivity was primarily the result of more robust fold changes measured by the oligonucleotide system. Essentially all gene changes overlapping between the two platforms were co-directional, and ranged from 4 to 19% depending upon the amount of biological variability within and between the comparison groups. Q-PCR validation rates were virtually identical for the two platforms, with 23-24% validation in the prefrontal cortex experiment, and 56% for both platforms in the cell culture experiment. Validated genes included dopa decarboxylase, dopamine beta-hydroxylase, and dihydropyrimidinase-related protein 3, which were decreased in NBFL cells exposed to valproate, and spinocerebellar ataxia 7, which was increased in bipolar disease. The modest overlap but similar validation rates show that each microarray system identifies a unique set of differentially expressed genes, and thus the greatest information is obtained from the use of both platforms.

The antipsychotic aripiprazole is a potent, partial agonist at the human 5-HT1A receptor.

Aripiprazole, 7-[4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy]-3,4-dihydro-2(1H)-quinolinone, a novel antipsychotic with partial agonist activity at dopamine D2 receptors, bound with high affinity to recombinant human 5-HT(1A) receptors (h5-HT(1A)) in Chinese hamster ovary cell membranes and displayed potent, partial agonism at 5-HT(1A) receptors in a guanosine-5'-O-(3-[(35)S]thio)-triphosphate ([(35)S]GTP gamma S)-binding assay that was blocked completely by a selective 5-HT(1A) receptor antagonist. An interaction with 5-HT(1A) receptors may contribute to the overall efficacy of aripiprazole against symptoms of schizophrenia, including anxiety, depression, cognitive and negative symptoms, and to its favorable side-effect profile. Combined with previous studies demonstrating the potent partial agonism of aripiprazole at dopamine D2 receptors, this study suggests aripiprazole is the first dopamine-serotonin system stabilizer.

In vivo effects of aripiprazole on cortical and striatal dopaminergic and serotonergic function.

In vivo microdialysis was used to monitor the effects of oral aripiprazole and olanzapine on basal extracellular concentrations of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) in the medial prefrontal cortex and striatum of conscious, freely moving rats. Acute aripiprazole administration did not affect dopamine output, but produced moderate increases in DOPAC and HVA concentrations, in medial prefrontal cortex or striatum of drug-naïve rats. Similarly, aripiprazole did not affect dopamine output but produced moderate elevations in DOPAC and HVA concentrations in the striatum of chronic aripiprazole-pretreated rats. Olanzapine produced comparatively larger elevations in dopamine, DOPAC, and HVA in both regions, which, in the striatum, were diminished after chronic olanzapine exposure. Aripiprazole reduced extracellular 5-HIAA concentrations in the medial prefrontal cortex and striatum of drug-nai;ve rats, but not in chronic aripiprazole-pretreated rats. Together, these data provide in vivo evidence of aripiprazole-induced changes in forebrain dopaminergic and serotonergic function that may reflect its partial agonist activity at presynaptic dopamine D(2) and 5-HT(1A) receptors and antagonist activity at 5-HT(2A) receptors.

Diminished catalepsy and dopamine metabolism distinguish aripiprazole from haloperidol or risperidone.

Catalepsy and changes in striatal and limbic dopamine metabolism were investigated in mice after oral administration of aripiprazole, haloperidol, and risperidone. Catalepsy duration decreased with chronic (21 day) aripiprazole compared with acute (single dose) treatment across a wide dose range, whereas catalepsy duration persisted with chronic haloperidol treatment. At the time of maximal catalepsy, acute aripiprazole did not alter neostriatal dopamine metabolite/dopamine ratios or homovanillic acid (HVA) levels, and produced small increases in dihydroxyphenylacetic acid (DOPAC). Effects were similar in the olfactory tubercle. Dopamine metabolism was essentially unchanged in both regions after chronic aripiprazole. Acute treatments with haloperidol or risperidone elevated DOPAC, HVA, and metabolite/dopamine ratios in both brain areas and these remained elevated with chronic treatment. The subtle effects of aripiprazole on striatal and limbic dopamine metabolism, and the decrease in catalepsy with chronic administration, illustrate fundamental differences in dopamine neurochemical actions and behavioral sequelae of aripiprazole compared to haloperidol or risperidone.