Amisulpride the 'atypical' atypical antipsychotic--comparison to haloperidol, risperidone and clozapine

Effects of a single dose of amisulpride on functional brain changes during reward- and motivation-related processing using task-based fMRI in healthy subjects and patients with major depressive disorder - study protocol for a randomized clinical trial

BACKGROUND

Anhedonia and other deficits in reward- and motivation-related processing in psychiatric patients, including patients with major depressive disorder (MDD), represent a high unmet medical need. Neurobiologically, these deficits in MDD patients are mainly associated with low dopamine function in a frontostriatal network. In this study, alterations in brain activation changes during reward processing and at rest in MDD patients compared with healthy subjects are explored and the effects of a single low dose of the dopamine D2 receptor antagonist amisulpride are investigated.

METHODS

This is a randomized, controlled, double-blind, single-dose, single-center parallel-group clinical trial to assess the effects of a single dose of amisulpride (100 mg) on blood-oxygenation-level-dependent (BOLD) responses during reward- and motivation-related processing in healthy subjects (n = 60) and MDD patients (n = 60). Using functional magnetic resonance imaging (fMRI), BOLD responses are assessed during the monetary incentive delay (MID) task (primary outcome). Exploratory outcomes include BOLD responses and behavioral measures during the MID task, instrumental learning task, effort-based decision-making task, social incentive delay task, and probabilistic reward task as well as changes in resting state functional connectivity and cerebral blood flow.

DISCUSSION

This study broadly covers all aspects of reward- and motivation-related processing as categorized by the National Institute of Mental Health Research Domain Criteria and is thereby an important step towards precision psychiatry. Results regarding the immediate effects of a dopaminergic drug on deficits in reward- and motivation-related processing not only have the potential to significantly broaden our understanding of underlying neurobiological processes but might eventually also pave the way for new treatment options.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05347199. April 12, 2022.

Interaction of amisulpride with GLUT1 at the blood-brain barrier. Relevance to Alzheimer's disease

Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.

Dopamine Dynamics and Neurobiology of Non-Response to Antipsychotics, Relevance for Treatment Resistant Schizophrenia: A Systematic Review and Critical Appraisal

Treatment resistant schizophrenia (TRS) is characterized by a lack of, or suboptimal response to, antipsychotic agents. The biological underpinnings of this clinical condition are still scarcely understood. Since all antipsychotics block dopamine D2 receptors (D2R), dopamine-related mechanisms should be considered the main candidates in the neurobiology of antipsychotic non-response, although other neurotransmitter systems play a role. The aims of this review are: (i) to recapitulate and critically appraise the relevant literature on dopamine-related mechanisms of TRS; (ii) to discuss the methodological limitations of the studies so far conducted and delineate a theoretical framework on dopamine mechanisms of TRS; and (iii) to highlight future perspectives of research and unmet needs. Dopamine-related neurobiological mechanisms of TRS may be multiple and putatively subdivided into three biological points: (1) D2R-related, including increased D2R levels; increased density of D2Rs in the high-affinity state; aberrant D2R dimer or heteromer formation; imbalance between D2R short and long variants; extrastriatal D2Rs; (2) presynaptic dopamine, including low or normal dopamine synthesis and/or release compared to responder patients; and (3) exaggerated postsynaptic D2R-mediated neurotransmission. Future points to be addressed are: (i) a more neurobiologically-oriented phenotypic categorization of TRS; (ii) implementation of neurobiological studies by directly comparing treatment resistant vs. treatment responder patients; (iii) development of a reliable animal model of non-response to antipsychotics.

Pharmacological strategies for sexual recovery in men undergoing antipsychotic treatment

INTRODUCTION

: First- and second-generation antipsychotics are highly accountable for causing a plethora of medical side effects, ranging from metabolic imbalances to sexual dysfunction (SD), that frequently undermine patient-doctor relationships. Nevertheless, to date antipsychotics are one of the best treatment options for dealing with numerous either acute or chronic conditions like agitation, suicidality, depression, dementia, and of course psychosis. For these reasons, clinicians need to handle them wisely to preserve patients' sexual health, avoid poor therapeutic adherence and prevent high rates of therapy drop-out.

AREAS COVERED

: This article reviews the literature on pharmacologic approaches for management strategies in men who are administered with antipsychotics and developed SD. The etiology of antipsychotic-induced SD is also discussed.

EXPERT OPINION

: Clinicians must consider sexual life as a major health domain. To do so, a first step would be to measure and monitor sexual function by means of psychometric tools. Secondly, primary prevention should be conducted when choosing antipsychotics, i.e., picking sex-sparing compounds like aripiprazole or brexpiprazole. Thirdly, if sexolytic compounds cannot be dismissed, such as first-generation antipsychotics, risperidone, paliperidone, or amisulpride, then aripiprazole 5-20 mg/day adjunctive therapy has proven to be most effective in normalizing prolactin levels and consequently treating antipsychotic-induced SD.

Pharmacology profile of F17464, a dopamine D3 receptor preferential antagonist

F17464 (N-(3-{4-[4-(8-Oxo-8H-[1,3]-dioxolo-[4,5-g]-chromen-7-yl)-butyl]-piperazin-1-yl}-phenyl)-methanesulfonamide, hydrochloride) is a new potential antipsychotic with a unique profile. The compound exhibits high affinity for the human dopamine receptor subtype 3 (hD3) (Ki = 0.17 nM) and the serotonin receptor subtype 1a (5-HT1a) (Ki = 0.16 nM) and a >50 fold lower affinity for the human dopamine receptor subtype 2 short and long form (hD2s/l) (Ki = 8.9 and 12.1 nM, respectively). [14C]F17464 dynamic studies show a slower dissociation rate from hD3 receptor (t1/2 = 110 min) than from hD2s receptor (t1/2 = 1.4 min) and functional studies demonstrate that F17464 is a D3 receptor antagonist, 5-HT1a receptor partial agonist. In human dopaminergic neurons F17464 blocks ketamine induced morphological changes, an effect D3 receptor mediated. In vivo F17464 target engagement of both D2 and 5-HT1a receptors is demonstrated in displacement studies in the mouse brain. F17464 increases dopamine release in the rat prefrontal cortex and mouse lateral forebrain - dorsal striatum and seems to reduce the effect of MK801 on % c-fos mRNA medium expressing neurons in cortical and subcortical regions. F17464 also rescues valproate induced impairment in a rat social interaction model of autism. All the neurochemistry and behavioural effects of F17464 are observed in the dose range 0.32-2.5 mg/kg i.p. in both rats and mice. The in vitro - in vivo pharmacology profile of F17464 in preclinical models is discussed in support of a therapeutic use of the compound in schizophrenia and autism.

Clozapine reliably increases the motivation for food: parsing the role of the 5-HT2c and H1 receptors

RATIONALE AND OBJECTIVES

Although clozapine is effective in treating schizophrenia, it is associated with adverse side effects including weight gain and metabolic syndrome. Despite this, the role of clozapine on feeding behaviour and food intake has not been thoroughly characterised. Clozapine has a broad pharmacological profile, with affinities for several neurotransmitter receptors, including serotonin (5-hydroxytriptamine, 5-HT) and histamine. Given that the serotonin 5-HT_2C receptor and histaminergic H₁ receptor are involved in aspects of feeding behaviour, the effect of clozapine on feeding may be linked to its action at these receptors.

METHODS

We assessed, in rats, the effect of acute and subchronic administration of clozapine on responding for food under a progressive ratio (PR) schedule under conditions of food restriction and satiety. We also examined the effect of antagonists of the serotonin 5-HT_2C and histaminergic H₁ receptors on the same schedule. Clozapine reliably increased responding for food, even when rats had ad libitum access to food. The effect of clozapine on responding for food was reproduced by combined (but not individual) antagonism of the serotonin 5-HT_2C and histaminergic H₁ receptors.

CONCLUSION

These findings show that clozapine enhances the motivation to work for food, that this effect is stable over repeated testing, and is independent of hunger state of the animal. This effect may relate to a combined action of clozapine at the serotonin 5-HT_2C and histaminergic H₁ receptors.

c-Fos and FosB/ΔFosB colocalizations in selected forebrain structures after olanzapine, amisulpride, aripiprazole, and quetiapine single administration in rats preconditioned by two different mild stressors sequences

OBJECTIVE

Olanzapine (OLA), amisulpride (AMI), aripiprazole (ARI), and quetiapine (QUE) belong to antipsychotics, which administration represents still most reliable way for the treatment of schizophrenic and bipolar disorders. The intention of the present study was to explore whether the acute administration of a particular antipsychotic, indicated by the presence of c-Fos, will: a) stimulate neurons already activated by a long lasting homogeneous or heterogeneous stress preconditioning, indicated by the FosB/ΔFosB (ΔFosB) expression, or b) have a stimulatory effect only on a not activated, so called silent neurons. The pattern of ΔFosB and c-Fos spatial relationship was investigated in three forebrain structures, including the septal ventrolateral nucleus (seVL), the striatal dorsolateral area (stDL), and the shell of the nucleus accumbens (shell).

METHODS

The rats were divided into 10 groups and exposed to two types of stressors. Half of them was exposed to a sequence of homogeneous stressor - handling (HDL) and the other half to a heterogeneous stressor (CMS) daily for 20 days. CMS consisted of five types of stressors: crowding, air-puff, wet bedding, predator stress, and forced swimming applied in an unexpected order. On the 21st day of the experiment, the rats were free of the stress exposure and on the 22nd day, both groups of animals receive a single intraperitoneal injection of vehicle (4% DMSO in saline, 0.1 ml/100 g) or OLA (5 mg/kg), AMI (20 mg/kg), ARI (10 mg/kg), and QUE (15 mg/kg). 90 min after the drugs administration the animals were transcardially perfused, brains removed, cut into 30 µm thick coronal sections, and double stained: first with ΔFosB antibody linked with Alexa488 fluorescent dye and second with c-Fos antibody linked to Alexa596 one. Quantitative evaluation of ΔFosB and c-Fos colocalizations was performed on fluorescence photomicrographs transformed into a final picture containing only yellow, green, and red colored circles.

RESULTS

The data of this investigation demonstrate that ΔFosB and c-Fos colocalizations occurred in each of the three areas investigated, i.e. seVL, stDL, and shell ones, in both HDL as well as CMS preconditioned rats. The levels of ΔFosB and c-Fos colocalizations varied in the individual forebrain areas studied. From the total 22 areas measured, level of c-Fos colocalization prevailed over ΔFosB in 18 ones. However, neither c-Fos nor ΔFosB reached 100% level of colocalization in any of the forebrain areas investigated.

CONCLUSION

The present findings indicate that ΔFosB and c-Fos colocalizations occurred in each of the three areas investigated, i.e. seVL, stDL, and shell, in both HDL and CMS preconditioned rats, whereas the parallel occurrence of free c-Fos as well as c-Fos colocalized with ΔFosB might speak out for a possible involvement of the c-Fos activated by antipsychotics applied in dual, i.e. short- and long-lasting, functions.

Region-specific blood-brain barrier transporter changes leads to increased sensitivity to amisulpride in Alzheimer's disease

BACKGROUND

Research into amisulpride use in Alzheimer's disease (AD) implicates blood-brain barrier (BBB) dysfunction in antipsychotic sensitivity. Research into BBB transporters has been mainly directed towards the ABC superfamily, however, solute carrier (SLC) function in AD has not been widely studied. This study tests the hypothesis that transporters for organic cations contribute to the BBB delivery of the antipsychotics (amisulpride and haloperidol) and is disrupted in AD.

METHODS

The accumulation of [3H]amisulpride (3.7-7.7 nM) and [3H]haloperidol (10 nM) in human (hCMEC/D3) and mouse (bEnd.3) brain endothelial cell lines was explored. Computational approaches examined molecular level interactions of both drugs with the SLC transporters [organic cation transporter 1 (OCT1), plasma membrane monoamine transporter (PMAT) and multi-drug and toxic compound extrusion proteins (MATE1)] and amisulpride with the ABC transporter (P-glycoprotein). The distribution of [3H]amisulpride in wildtype and 3×transgenic AD mice was examined using in situ brain perfusion experiments. Western blots determined transporter expression in mouse and human brain capillaries .

RESULTS

In vitro BBB and in silico transporter studies indicated that [3H]amisulpride and [3H]haloperidol were transported by the influx transporter, OCT1, and efflux transporters MATE1 and PMAT. Amisulpride did not have a strong interaction with OCTN1, OCTN2, P-gp, BCRP or MRP and could not be described as a substrate for these transporters. Amisulpride brain uptake was increased in AD mice compared to wildtype mice, but vascular space was unaffected. There were no measurable changes in the expression of MATE1, MATE2, PMAT OCT1, OCT2, OCT3, OCTN1, OCTN2 and P-gp in capillaries isolated from whole brain homogenates from the AD mice compared to wildtype mice. Although, PMAT and MATE1 expression was reduced in capillaries obtained from specific human brain regions (i.e. putamen and caudate) from AD cases (Braak stage V-VI) compared to age matched controls (Braak stage 0-II).

CONCLUSIONS

Together our research indicates that the increased sensitivity of individuals with Alzheimer's to amisulpride is related to previously unreported changes in function and expression of SLC transporters at the BBB (in particular PMAT and MATE1). Dose adjustments may be required for drugs that are substrates of these transporters when prescribing for individuals with AD.

Impaired Gastric Hormone Regulation of Osteoblasts and Lysyl Oxidase Drives Bone Disease in Diabetes Mellitus

Diabetic bone disease is a complication of type I and type II diabetes, both of which are increasing in the United States and elsewhere. Increased hip and foot fracture rates do not correlate well with changes in bone mineral density (BMD), whereas studies support the importance of collagen structure to bone strength. Extracellular lysyl oxidase (LOX) catalyzes the oxidative deamination of hydroxylysine and lysine residues in collagens resulting in aldehydes that subsequently form critically important biosynthetic crosslinks that stabilize functional collagens. Although LOX-dependent biosynthetic crosslinks in bone collagen are deficient in diabetic bone, the expression and regulation of bone LOXs in diabetes have not been comprehensively studied. Here, we found that LOX is profoundly downregulated in bone in diabetes. Moreover, we have identified a novel metabolic regulatory relationship that is dysregulated in diabetes using mouse models. Data indicate that the incretin (gastric hormone) known as glucose-dependent insulinotropic polypeptide (GIP) that is anabolic to osteoblasts strongly upregulates LOX, and that this regulation is disrupted in the streptozotocin-induced model of diabetes in mice. In vivo and in vitro studies support that diabetes results in elevated circulating peripheral dopamine, likely also derived from the gut, and is responsible for blocking GIP signaling and LOX levels in osteoblasts. Moreover, peripheral administration of the dopamine D2 receptor antagonist amisulpride to diabetic mice restored trabecular bone structure to near normal and partially reversed downregulation of LOX. Taken together our data identifies a novel metabolic relationship between the gut-derived hormone GIP and bone-derived LOX, and points to the importance of LOX dysregulation in the pathology of diabetic bone disease. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Brexpiprazole has a low risk of dopamine D2 receptor sensitization and inhibits rebound phenomena related to D2 and serotonin 5-HT2A receptors in rats

Background

Long‐term antipsychotic treatment in patients with schizophrenia can induce supersensitivity psychosis and tardive dyskinesia which is thought to be caused by dopamine D₂ receptor sensitization. We evaluated the effects of brexpiprazole on D₂ receptor sensitivity after subchronic treatment in rats. We also evaluated whether brexpiprazole could suppress enhanced response to D₂ receptors in rats subchronically dosed with another atypical antipsychotic.

Methods

The maximum D₂ receptor density (B_max) and apomorphine (a D₂ receptor agonist)‐induced stereotypy were measured in rats orally dosed with vehicle, haloperidol (1 mg/kg), or brexpiprazole (4 or 30 mg/kg for B_max, 6 or 30 mg/kg for stereotypy) for 21 days. Then, effects of oral administrations of brexpiprazole (3 mg/kg), aripiprazole (10 mg/kg), and olanzapine (3 mg/kg) against increases in apomorphine‐induced hyperlocomotion and (±)‐2,5‐dimethoxy‐4‐iodoamphetamine hydrochloride (DOI: a 5‐HT_2A receptor agonist)‐induced head twitches were evaluated in rats subcutaneously treated with risperidone (1.5 mg/kg/d) via minipumps for 21 days.

Results

Haloperidol and brexpiprazole (30 mg/kg: approximately tenfold ED₅₀ of anti‐apomorphine‐induced stereotypy) but not brexpiprazole (4 or 6 mg/kg) significantly increased the B_max and apomorphine‐induced stereotypy. Brexpiprazole (3 mg/kg) and olanzapine (3 mg/kg) significantly suppressed both increases in apomorphine‐induced hyperlocomotion and also DOI‐induced head twitches in rats subchronically treated with risperidone, but aripiprazole (10 mg/kg) significantly suppressed only apomorphine‐induced hyperlocomotion.

Conclusion

Brexpiprazole has a low risk of D₂ receptor sensitization after a repeated administration and suppresses the rebound phenomena related to D₂ and 5‐HT_2A receptors after a repeated administration of risperidone.

Brexpiprazole has less potential to evoke dopamine D2 receptor supersensitivity in rats after repeated administration compared to haloperidol. In addition, brexpiprazole may have a lower risk for producing rebound symptoms associated with D2 receptor, 5‐HT2A receptor sensitization when switching from other antipsychotics such as risperidone.

Antipsychotic Benzamides Amisulpride and LB-102 Display Polypharmacy as Racemates, S Enantiomers Engage Receptors D2 and D3, while R Enantiomers Engage 5-HT7

Benzamide antipsychotics such as amisulpride are dosed as racemates though efficacy is assumed to be mediated through S enantiomer binding to D2 receptors. At prescribed doses, the benzamides likely display polypharmacy since brain exposure should be sufficient to engage the 5-HT7 receptors, as well. Curiously, the studies herein reveal that racemic dosing is required to engage both targets since the D2 receptor has an almost 40-fold selectivity for the S enantiomer, while the 5-HT7 receptor has greater than 50-fold preference for the R enantiomer.

Clozapine reduces nicotine self-administration, blunts reinstatement of nicotine-seeking but increases responding for food

People with schizophrenia display significantly higher rates of smoking than the general population, which may be due to an interaction between nicotine and antipsychotic medication. While the conventional antipsychotic drug haloperidol sometimes increases cigarette smoking in patients with schizophrenia, there is some evidence suggesting that clozapine, an atypical antipsychotic drug, may reduce nicotine use in these patients. However, the effects of antipsychotic drugs like clozapine on aspects of nicotine self-administration and reinstatement have not been systematically examined. In the current study, we assessed the effect of clozapine on nicotine self-administration under fixed ratio and progressive ratio schedules of reinforcement, as well as reinstatement of nicotine-seeking following a period of abstinence. To determine the specificity of its effect on nicotine reward, we also tested the effect of clozapine on responding for food reinforcement under fixed ratio and progressive ratio schedules. For comparison, we also examined the effects of haloperidol, a first-generation antipsychotic drug, under some of the same behavioral conditions as clozapine. We show that clozapine inhibits nicotine self-administration and reinstatement of nicotine-seeking but also increases the amount of effort that rats will exert for food reward. In contrast, haloperidol at a wide range of doses attenuated responding for nicotine and food reward, suggestive of a non-specific reduction in reinforcer efficacy. These results show the potential utility of clozapine as a smoking cessation treatment for patients with schizophrenia, in addition to its antipsychotic properties.

Spatial relationship between the c-Fos distribution and enkephalinergic, substance P, and tyrosine hydroxylase innervation fields after acute treatment with neuroleptics olanzapine, amisulpride, quetiapine, and aripiprazole in the rat septum

OBJECTIVE

The aim of the present study was to demonstrate the spatial relationship between the c-Fos immunoreactive cells elicited by an acute treatment with neuroleptics including amisulpride (AMI), olanzapine (OLA), quetiapine (QUE), and aripiprazole (ARI) and enkephalinergic (ENK), substance P (SP), and tyrosine hydroxylase (TH) innervation fields in the rat septum.

METHODS

Male Sprague Dawley rats received a single injection of OLA (5 mg), ARI (10 mg), AMI (20 mg), QUE (15 mg/kg/b.w.). Ninety min after antipsychotics administration, the animals were transcardially perfused with a fixative and the brains cryocut into serial coronal sections of 35 µm thickness. The sections were processed for c-Fos staining using an avidin-biotin-peroxidase complex and visualized by nickel intensified diaminobenzidine to reach black endproduct. Afterwards, the sections were exposed to ENK, SP, and TH antibodies and the reaction product visualized by biotin-labeled fluorescent AlexaFluor 564 dye. The data were evaluated from the sections either simultaneously illuminated with fluorescent and transmission microscope beams or after merging the separately illuminated sections in the Adobe Photoshop 7.0 software.

RESULTS

ENK, SP, and TH displayed characteristic spatial images formed by a dense accumulation of immunoreactive fibers and terminals on the both sides of the septum. A dense plexus of axons formed by ENK and SP immunopositive terminals were situated predominantly in the lateral, while TH ones more medial portion of the septum. QUE and AMI activated distinct amount of c-Fos expression in cells located within the SP-immunoreactive principal innervation field. The OLA effect on the c-Fos expression was very pronounced in the ventral TH-labeled principal innervation field including the space between the ENK field ventral portion and the dorsal margin of the accumbens nucleus shell. Generally, the occurrence of c-Fos cells in the ENK-immunoreactive principal innervation field, in comparison with the surrounding septal area, was less abundant after all of the four antipsychotics treatments.

CONCLUSION

The data of the present study indicate that ENK, SP, and TH innervation fields may influence separate populations of septal cells activated by AMI, OLA, QUE, and ARI and that each of these region-differently innervated cells may be associated with the functional heterogeneity of the individual lateral septal nuclei.

Blonanserin ameliorates social deficit through dopamine-D3 receptor antagonism in mice administered phencyclidine as an animal model of schizophrenia

Blonanserin differs from other antipsychotic drugs, such as risperidone and olanzapine, and exhibits a higher affinity for dopamine-D_2/3 receptors than for serotonin 5-HT_2A receptors. We investigated the involvement of dopamine-D₃ receptors in the effect of blonanserin on the social deficit observed in an animal model of schizophrenia and sought to elucidate the molecular mechanism underlying its action. Mice received phencyclidine (PCP: 10 mg/kg/day, s.c.), a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, once a day for 14 consecutive days. We then evaluated the sociability, using a social interaction test, and the expression of GluN1 subunit, an essential subunit of the NMDA receptors, in these mice. Blonanserin significantly ameliorated the PCP-induced social deficit, whereas olanzapine and haloperidol did not. This effect of blonanserin was antagonized by 7-OH-DPAT, a dopamine-D₃ receptor agonist, and SCH23390, a dopamine-D₁ receptor antagonist. However, the ameliorating effect of blonanserin was not inhibited by DOI, a serotonin 5-HT_2A receptor agonist. The PCP-induced social deficit was also ameliorated by U99194, a dopamine-D₃ receptor antagonist and SKF38393, a dopamine-D₁ receptor agonist, being effects antagonized by 7-OH-DPAT or SCH23390. Blonanserin significantly inhibited the decrease in the phosphorylation levels of GluN1 at Ser⁸⁹⁷ by protein kinase A (PKA) in the prefrontal cortex (PFC) in PCPadministered mice. These results suggest that activation of NMDA receptors due to Ser⁸⁹⁷-phosphorylation of GluN1 subunit, which is a step linked to dopamine-D₁ receptor-PKA signaling through dopamine-D₃ receptor antagonism in the PFC, is required for the ameliorating effect of blonanserin on the PCP-induced social deficit. These findings also provide in vivo evidence that blonanserin antagonism of the dopamine-D₃ receptors may be useful as a novel treatment strategy and that the dopamine-D₃ receptors can be a novel therapeutic target molecule for the social deficit observed in schizophrenia.

Antipsychotics and pituitary tumors: an analysis of the European pharmacovigilance database (EudraVigilance)

One of the possible long-term consequences of antipsychotic-induced hyperprolactinemia is the development of pituitary tumors - prolactinomas. So far, two pharmacovigilance studies of spontaneous adverse event report databases have suggested an increased risk, whereas a longitudinal study carried out with risperidone showed no evidence of increased risk of tumors with mass effect. Besides, information on amisulpride and paliperidone is lacking. Thus, in this study, we aimed to analyze the European pharmacovigilance database (EudraVigilance) to shed light on this issue. We searched for all suspected spontaneous cases of pituitary tumors associated with antipsychotics in EudraVigilance up to 23 March 2017. To assess the association between pituitary tumor cases and each antipsychotic, we calculated the proportional reporting ratios. Among 4 964 866 events of all types recorded in EudraVigilance, we found 292 cases of pituitary tumors associated with antipsychotics. All atypical antipsychotics except clozapine fulfilled the criteria to generate a safety signal. The highest proportional reporting ratio values were found for amisulpride 51.57 (36.3-73.2), risperidone 21.83 (18.4-25.8), and paliperidone 19.95 (14.7-27.1). Sulpiride and haloperidol showed a higher risk among typical antipsychotics 12.4 (5.89-26.1) and 7.0 (4.35-11.3). Notably, we found that a mass effect was present in 16% of the cases. Besides, 18 cases occurred in patients aged below 18 years. Our analysis of the data in EudraVigilance confirms the safety signal detected by previous studies. Interestingly, for the first time, we show that the association seems to be the strongest for amisulpride and that a mass effect was present in around 16% of the cases.

Clozapine in the Treatment of Aggression in Conduct Disorder in Children and Adolescents: A Randomized, Double-blind, Controlled Trial

Objective

This study was conducted to compare the efficacy of clozapine vs. risperidone in the treatment of aggression in conduct disorder in children and adolescents.

Methods

Twenty-four children with conduct disorder aged 6 to 16 years were randomized in a prospective, double-blind trial into two groups to receive clozapine or risperidone for 16 weeks. The Modified Overt Aggression Scale score was used as the primary outcome of the study. Secondary outcomes were Child Behavior Checklist (CBCL) externalization (CBCL-E) and internalization factors; Aggression, Hyperactivity and Delinquency subscales of CBCL-E, Child Global Assessment Scale (CGAS), Barnes Akathisia Rating Scale, and Simpson-Angus Scale.

Results

Both antipsychotics were similarly effective in the primary outcome and in most of the secondary ones. Clozapine was more effective in CBCL-E, the delinquency subscale and the CGAS scores than risperidone (p =0.039, 0.010, and 0.021). Two subjects from the clozapine group were excluded due to a low neutrophil count at week four.

Conclusion

Clozapine and risperidone are effective for short-term treatment of aggression in children and adolescents with conduct disorder. Clozapine was more effective than risperidone in conduct externalization factors, delinquency trait and global functioning in children and adolescents. Stronger efficacy of clozapine should be investigated in larger sample sizes using pharmacogenomic studies. White blood cell counts need to be monitored when prescribing clozapine.

Amisulpride and olanzapine followed by open-label treatment with clozapine in first-episode schizophrenia and schizophreniform disorder (OPTiMiSE): a three-phase switching study

BACKGROUND

No established treatment algorithm exists for patients with schizophrenia. Whether switching antipsychotics or early use of clozapine improves outcome in (first-episode) schizophrenia is unknown.

METHODS

This three-phase study was done in 27 centres, consisting of general hospitals and psychiatric specialty clinics, in 14 European countries and Israel. Patients aged 18-40 years who met criteria of the DSM-IV for schizophrenia, schizophreniform disorder, or schizoaffective disorder were treated for 4 weeks with up to 800 mg/day amisulpride orally in an open-label design (phase 1). Patients who did not meet symptomatic remission criteria at 4 weeks were randomly assigned to continue amisulpride or switch to olanzapine (≤20 mg/day) during a 6-week double-blind phase, with patients and staff masked to treatment allocation (phase 2). Randomisation was done online by a randomisation website; the application implemented stratification by site and sex, and applied the minimisation method for randomisation. Patients who were not in remission at 10 weeks were given clozapine (≤900 mg/day) for an additional 12 weeks in an open-label design (phase 3). The primary outcome was the number of patients who achieved symptomatic remission at the final visits of phases 1, 2, and 3, measured by intention-to-treat analysis. Data were analysed with a generalised linear mixed model, with a logistic link and binomial error distribution. This trial is registered with ClinicalTrials.gov, number NCT01248195, and closed to accrual.

FINDINGS

Between May 26, 2011, and May 15, 2016, we recruited 481 participants who signed informed consent. Of the 446 patients in the intention-to-treat sample, 371 (83%) completed open-label amisulpride treatment, and 250 (56%) achieved remission after phase 1. 93 patients who were not in remission continued to the 6-week double-blind switching trial, with 72 (77%) patients completing the trial (39 on olanzapine and 33 on amisulpride); 15 (45%) patients on amisulpride versus 17 (44%) on olanzapine achieved remission (p=0·87). Of the 40 patients who were not in remission after 10 weeks of treatment, 28 (70%) started on clozapine; 18 (64%) patients completed the 12-week treatment, and five (28%) achieved remission. The number of serious adverse events did not differ between the treatment arms in phase 2: one patient on olanzapine was admitted to hospital because of an epileptic seizure, and one patient on amisulpride was admitted to hospital twice because of exacerbations of psychotic symptoms. Over the course of the trial, two serious suicide attempts were reported.

INTERPRETATION

For most patients in the early stages of schizophrenia, symptomatic remission can be achieved using a simple treatment algorithm comprising the sequential administration of amisulpride and clozapine. Since switching to olanzapine did not improve outcome, clozapine should be used after patients fail a single antipsychotic trial-not until two antipsychotics have been tried, as is the current recommendation.

FUNDING

European Commission Seventh Framework Program.

Review of serum prolactin levels as an antipsychotic-response biomarker

Antipsychotics acting as antagonists at dopamine D2 receptors concentrated in the striatum are the cornerstone of effective treatment of psychosis. Substantial progress in treating persons with schizophrenia could be achieved by the identification of biomarkers which reliably determine the lowest efficacious dose of antipsychotics. Prolactin levels have been considered a promising treatment-response biomarker due to dopamine’s regulation of serum prolactin levels through D2 receptors in the hypothalamic-pituitary pathway. Prolactin secretion in response antipsychotic administration is associated with the antipsychotics affinity for D2 receptors. This review assesses the available literature on the use of serum prolactin levels as an antipsychotic-response biomarker. Articles were identified through PubMed as well as the reference lists of full text articles available online. Relevant publications were summarized briefly to define the limitations and utility of serum prolactin levels as a tool for improving antipsychotic dosing. Serum prolactin levels in combination with prolactin-inducing potencies for each antipsychotic may help identify the lowest effective dose of antipsychotic medications. , In addition to the fact that prolactin secretion is dependent on serum antipsychotic levels and not brain levels, recent findings show that prolactin release is independent of the β-arrestin-2 pathway and GSK3β regulation, one branch of the pathway that has been implicated in antipsychotic efficacy. Therefore, serum prolactin is an indirect biomarker for treatment response. Further investigations are warranted to characterize prolactin-antipsychotic dose-response curves and systematically test the utility of measuring prolactin levels in patients to identify a person’s lowest efficacious dose.

Therapeutic D2/3 receptor occupancies and response with low amisulpride blood concentrations in very late-onset schizophrenia-like psychosis (VLOSLP)

OBJECTIVE

Antipsychotic drug sensitivity in very late-onset schizophrenia-like psychosis (VLOSLP) is well documented, but poorly understood. This study aimed to investigate blood drug concentration, D2/3 receptor occupancy and outcome in VLOSLP during open amisulpride prescribing, and compare this with Alzheimer's disease (AD).

METHODS

Blood drug concentration, prolactin, symptoms and extrapyramidal side-effects (EPS) were serially assessed during dose titration. [¹⁸ F]fallypride imaging was used to quantify D2/3 receptor occupancy. Average steady-state amisulpride concentration (Caverage, ng/ml) was estimated by incorporating pharmacokinetic (PK) data into an existing population PK model (25 AD participants, 20 healthy older people).

RESULTS

Eight patients (target 20) were recruited (six women; 76 + - 6 years; six treatment compliant; five serially sampled; three with paired imaging data). Mean + - SD symptom reduction was 74 ± 12% (50-100 mg/day; 92.5 + -39.4 ng/ml). Mild EPS emerged at 96 ng/ml (in AD, severe EPS, 50 mg/day, 60 ng/ml). In three participants, imaged during optimal treatment (50 mg/day; 41-70 ng/ml), caudate occupancy was 44-59% (58-74% in AD across a comparable Caverage).

CONCLUSIONS

Despite the small sample size, our findings are highly relevant as they suggest that, as in AD, 50 mg/day amisulpride is associated with >40% occupancy and clinically relevant responses in VLOSLP. It was not possible to fully characterise concentration-occupancy relationships in VLOSLP, and it is thus unclear whether the greater susceptibility of those with AD to emergent EPS was accounted for by increased central drug access. Further investigation of age- and diagnosis-specific threshold sensitivities is warranted, to guide amisulpride prescribing in older people, and therapeutic drug monitoring studies offer a potentially informative future approach. Copyright © 2017 John Wiley & Sons, Ltd.

Neuroleptic Malignant Syndrome with Minimal Dose of Amisulpride

Amisulpride is an atypical antipsychotic drug, it helps in alleviation of symptoms of psychotic illnesses. Extrapyramidal features have been reported after taking amisulpride. Neuroleptic malignant syndrome (NMS) with amisulpride is rare, and have been reported earlier. In all the earlier reported cases patient received more than 150 mg of amisulpride. To the best of our knowledge we are reporting a case of NMS with very minimal dose of Amisulpride (50 mg) taken for very short period.

Short- and long-term effects of risperidone on catalepsy sensitisation and acquisition of conditioned avoidance response: Adolescent vs adult rats

The effects of antipsychotic drugs (APDs) on the adolescent brain are poorly understood despite a dramatic increase in prescription of these drugs in adolescents over the past twenty years. Neuronal systems continue to be remodeled during adolescence. Therefore, when given in adolescence, antipsychotic drugs (APDs) have the potential to affect this remodeling. In this study we investigated the effects of chronic 22-day risperidone treatment (1.3mg/kg/day) in both adolescent and adult rats. We examined short- and long-term changes in behaviour (catalepsy, locomotion and conditioned avoidance response (CAR)), and dopaminergic and serotonergic neurochemistry in the striatum and the nucleus accumbens. Here, we report that, both during chronic treatment and after a lengthy drug-free interval, risperidone induced a sensitised cataleptic response regardless of the age of exposure. Selectively in adolescents, risperidone-induced catalepsy was inversely correlated with striatal dopamine turnover immediately after chronic treatment. After a drug-free interval, a significant proportion of rats with prior adolescent risperidone treatment also failed to acquire CAR to a defined criterion. Our data provide evidence that the same chronic risperidone treatment regimen can induce contrasting short- and long-term neural outcomes in the adolescent and adult brains.

Therapeutic window of dopamine D2/3 receptor occupancy to treat psychosis in Alzheimer's disease

See Caravaggio and Graff-Guerrero (doi:10.1093/awx023) for a scientific commentary on this article.Antipsychotic drugs, originally developed to treat schizophrenia, are used to treat psychosis, agitation and aggression in Alzheimer's disease. In the absence of dopamine D2/3 receptor occupancy data to inform antipsychotic prescribing for psychosis in Alzheimer's disease, the mechanisms underpinning antipsychotic efficacy and side effects are poorly understood. This study used a population approach to investigate the relationship between amisulpride blood concentration and central D2/3 occupancy in older people with Alzheimer's disease by combining: (i) pharmacokinetic data (280 venous samples) from a phase I single (50 mg) dose study in healthy older people (n = 20, 65-79 years); (ii) pharmacokinetic, 18F-fallypride D2/3 receptor imaging and clinical outcome data on patients with Alzheimer's disease who were prescribed amisulpride (25-75 mg daily) to treat psychosis as part of an open study (n = 28; 69-92 years; 41 blood samples, five pretreatment scans, 19 post-treatment scans); and (iii) 18F-fallypride imaging of an antipsychotic free Alzheimer's disease control group (n = 10, 78-92 years), to provide additional pretreatment data. Non-linear mixed effects modelling was used to describe pharmacokinetic-occupancy curves in caudate, putamen and thalamus. Model outputs were used to estimate threshold steady state blood concentration and occupancy required to elicit a clinically relevant response (>25% reduction in scores on delusions, hallucinations and agitation domains of the Neuropsychiatric Inventory) and extrapyramidal side effects (Simpson Angus Scale scores > 3). Average steady state blood levels were low (71 ± 30 ng/ml), and associated with high D2/3 occupancies (65 ± 8%, caudate; 67 ± 11%, thalamus; 52 ± 11%, putamen). Antipsychotic clinical response occurred at a threshold concentration of 20 ng/ml and D2/3 occupancies of 43% (caudate), 25% (putamen), 43% (thalamus). Extrapyramidal side effects (n = 7) emerged at a threshold concentration of 60 ng/ml, and D2/3 occupancies of 61% (caudate), 49% (putamen) and 69% (thalamus). This study has established that, as in schizophrenia, there is a therapeutic window of D2/3 receptor occupancy for optimal treatment of psychosis in Alzheimer's disease. We have also shown that occupancies within and beyond this window are achieved at very low amisulpride doses in Alzheimer's disease due to higher than anticipated occupancies for a given blood drug concentration. Our findings support a central pharmacokinetic contribution to antipsychotic sensitivity in Alzheimer's disease and implicate the blood-brain barrier, which controls central drug access. Whether high D2/3 receptor occupancies are primarily accounted for by age- or disease-specific blood-brain barrier disruption is unclear, and this is an important future area of future investigation, as it has implications beyond antipsychotic prescribing.

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

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

Switching antipsychotics: Imaging the differential effect on the topography of postsynaptic density transcripts in antipsychotic-naïve vs. antipsychotic-exposed rats

The postsynaptic density (PSD) has been regarded as a functional switchboard at the crossroads of a dopamine-glutamate interaction, and it is putatively involved in the pathophysiology of psychosis. Indeed, it has been demonstrated that antipsychotics may modulate several PSD transcripts, such as PSD-95, Shank, and Homer. Despite switching antipsychotics is a frequent strategy to counteract lack of efficacy and/or side effect onset in clinical practice, no information is available on the effects of sequential treatments with different antipsychotics on PSD molecules. The aim of this study was to evaluate whether a previous exposure to a typical antipsychotic and a switch to an atypical one may affect the expression of PSD transcripts, in order to evaluate potential neurobiological correlates of this common clinical practice, with specific regards to putative synaptic plasticity processes. We treated male Sprague-Dawley rats intraperitoneally for 15days with haloperidol or vehicle, then from the sixteenth day we switched the animals to amisulpride or continued to treat them with vehicle or haloperidol for 15 additional days. In this way we got six first treatment/second treatment groups: vehicle/vehicle, vehicle/haloperidol, vehicle/amisulpride, haloperidol/vehicle, haloperidol/haloperidol, haloperidol/amisulpride. In this paradigm, we evaluated the expression of brain transcripts belonging to relevant and interacting PSD proteins, both of the Immediate-Early Gene (Homer1a, Arc) and the constitutive classes (Homer1b/c and PSD-95). The major finding was the differential effect of amisulpride on gene transcripts when administered in naïve vs. antipsychotic-pretreated rats, with modifications of the ratio between Homer1a/Homer1b transcripts and differential effects in cortex and striatum. These results suggest that the neurobiological effects on PSD transcripts of amisulpride, and possibly of other antipsychotics, may be greatly affected by prior antipsychotic treatments and may impact significantly on the switching procedure.

Improvement of ketamine-induced social withdrawal in rats: the role of 5-HT7 receptors

Social withdrawal, one of the core negative symptoms of schizophrenia, can be modelled in the social interaction (SI) test in rats using N-methyl-D-aspartate receptor glutamate receptor antagonists. We have recently shown that amisulpride, an antipsychotic with a high affinity for serotonin 5-HT7 receptors, reversed ketamine-induced SI deficits in rats. The aim of the present study was to further elucidate the potential involvement of 5-HT7 receptors in the prosocial action of amisulpride. Acute administration of amisulpride (3 mg/kg) and SB-269970 (1 mg/kg), a 5-HT7 receptor antagonist, reversed ketamine-induced social withdrawal, whereas sulpiride (20 or 30 mg/kg) and haloperidol (0.2 mg/kg) were ineffective. The 5-HT7 receptor agonist AS19 (10 mg/kg) abolished the prosocial efficacy of amisulpride (3 mg/kg). The coadministration of an inactive dose of SB-269970 (0.2 mg/kg) showed the prosocial effects of inactive doses of amisulpride (1 mg/kg) and sulpiride (20 mg/kg). The anxiolytic chlordiazepoxide (2.5 mg/kg) and the antidepressant fluoxetine (2.5 mg/kg) were ineffective in reversing ketamine-induced SI deficits. The present study suggests that the antagonism of 5-HT7 receptors may contribute towards the mechanisms underlying the prosocial action of amisulpride. These results may have therapeutic implications for the treatment of negative symptoms in schizophrenia and other disorders characterized by social withdrawal.

The effects of the dopamine stabilizer (-)-OSU6162 on aggressive and sexual behavior in rodents

The dopamine stabilizer (-)-OSU61612 dampens locomotion in rodents rendered hyperactive by exposure to a novel environment or treatment with amphetamine, but stimulates locomotion in habituated animals displaying low motor activity, tentatively exerting this profile by selectively blocking extrasynaptic D2 receptors. The major aim of the present study was to explore the possible usefulness of (-)-OSU61612 as an anti-aggressive drug. To this end, the effect of (-)-OSU61612 on isolation-induced aggression in male mice and estrous cycle-dependent aggression in female rats were studied using the resident intruder test; in addition, the possible influence of (-)-OSU61612 on sexual behavior in male mice and on elevated plus maze (EPM) performance in male rats were assessed. (-)-OSU61612 at doses influencing neither locomotion nor sexual activity reduced aggression in male mice. The effect was observed also in serotonin-depleted animals and is hence probably not caused by the antagonism of serotonin receptors displayed by the drug; refuting the possibility that it is due to 5-HT1B activation, it was also not counteracted by isamoltane. (-)-OSU61612 did not display the profile of an anxiogenic or anxiolytic drug in the EPM but caused a general reduction in activity that is well in line with the previous finding that it reduces exploratory behavior of non-habituated animals. In line with the observations in males, (-)-OSU61612 reduced estrus cycle-related aggression in female Wistar rats, a tentative animal model of premenstrual dysphoria. By stabilizing dopaminergic transmission, (-)-OSU61612 may prove useful as a well-tolerated treatment of various forms of aggression and irritability.

Partial agonism and fast dissociation of LASSBio-579 at dopamine D2 receptor

In an attempt to better understand the molecular mechanism of action of the antipsychotic lead LASSBio-579 and of its main metabolite LQFM 037, the aim of this work was to evaluate their intrinsic activity and binding kinetics at the dopamine D2 receptor. In transfected HEK cells expressing the D2L receptor under an inducible promoter, LASSBio-579 and LQFM 037, but not clozapine, behaved as weak partial agonists in [(35)S]-GTPγS binding assays performed in optimized conditions previously shown to evidence the partial agonist profile of aripiprazole. Besides, data obtained in radioligand competition assays on rat striatal membranes suggested a rapid association to and dissociation from the D2-like receptors. Using the kinetic rate index based on the strategy of the dual-point competition association assay, we showed that our compounds share a similar kinetic profile with clozapine, distinct from the typical antipsychotic haloperidol. These two characteristics could contribute to the atypical-like profile observed after administration of LASSBio-579 to rodents, in models of positive and negative symptoms of schizophrenia.

Second-generation antipsychotics and neuroleptic malignant syndrome: systematic review and case report analysis

BACKGROUND

Neuroleptic malignant syndrome (NMS) is a rare, severe, idiosyncratic adverse reaction to antipsychotics. Second-generation antipsychotics (SGAs) were originally assumed to be free from the risk of causing NMS, however several cases of NMS induced by SGAs (SGA-NMS) have been reported.

OBJECTIVES

The aim of this study was to systematically review available studies and case reports on SGA-NMS and compare the presentation of NMS induced by different SGAs.

DATA SOURCES

Citations were retrieved from PubMed up to November 2013, and from reference lists of relevant citations.

STUDY ELIGIBILITY CRITERIA

Eligibility criteria included (a) primary studies reporting data on NMS, with at least 50 % of the sample receiving SGAs; or (b) case reports and case reviews reporting on NMS induced by SGA monotherapy, excluding those due to antipsychotic withdrawal.

STUDY APPRAISAL AND SYNTHESIS METHODS

A standardized method for data extraction and coding was developed for the analysis of eligible case reports.

RESULTS

Six primary studies and 186 individual cases of NMS induced by SGAs were included. Primary studies suggest that SGA-NMS is characterized by lower incidence, lower clinical severity, and less frequent lethal outcome than NMS induced by first-generation antipsychotics. Systematic analysis of case reports suggests that even the most recently marketed antipsychotics are not free from the risk of inducing NMS. Furthermore, clozapine-, aripiprazole- and amisulpride-induced NMS can present with atypical features more frequently than other SGA-NMS, i.e. displaying less intense extrapyramidal symptoms or high fever.

LIMITATIONS

Case reports report non-systematic data, therefore analyses may be subject to bias.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Clinicians should be aware that NMS is virtually associated with all antipsychotics, including those most recently marketed. Although apparently less severe than NMS induced by older antipsychotics, SGA-NMS still represent a relevant clinical issue.

Effects of dopamine D2/D3 blockade on human sensory and sensorimotor gating in initially antipsychotic-naive, first-episode schizophrenia patients

It has been suggested that psychophysiological measures of sensory and sensorimotor gating, P50 gating and prepulse inhibition of the startle reflex (PPI), underlie core features of schizophrenia and are linked to dopaminergic pathways in the striatum and prefrontal cortex. In the present study, the effects of a potent D2/D3 receptor antagonist, amisulpride, were investigated on PPI and P50 gating in a large sample of antipsychotic-naive, first-episode patients with schizophrenia. A total of 52 initially antipsychotic-naive, first-episode schizophrenia patients were assessed for their P50 gating, PPI, and habituation/sensitization abilities at baseline and after 2 and 6 weeks of treatment with flexible doses of amisulpride. In addition, 47 matched healthy controls were assessed at baseline and after 6 weeks. At baseline, the patients showed significantly reduced PPI, yet normal levels of P50 gating, habituation, and sensitization. Treatment with amisulpride showed no effects on these measures, either at 2 or 6 weeks of follow-up. This is the first study investigating the effects of monotherapy with a relatively selective dopamine D2/D3 receptor antagonist (amisulpride) on sensory and sensorimotor gating deficits in a longitudinal study of a large group of initially antipsychotic-naive, first-episode patients with schizophrenia. Our finding that amisulpride effectively reduced symptom severity in our patients without reducing their PPI deficits indicates that increased activity of dopamine D2 receptors may be involved in symptomatology of patients with schizophrenia, but not in their sensorimotor gating deficits.

Influence of aripiprazole, risperidone, and amisulpride on sensory and sensorimotor gating in healthy 'low and high gating' humans and relation to psychometry

Despite advances in the treatment of schizophrenia spectrum disorders with atypical antipsychotics (AAPs), there is still need for compounds with improved efficacy/side-effect ratios. Evidence from challenge studies suggests that the assessment of gating functions in humans and rodents with naturally low-gating levels might be a useful model to screen for novel compounds with antipsychotic properties. To further evaluate and extend this translational approach, three AAPs were examined. Compounds without antipsychotic properties served as negative control treatments. In a placebo-controlled, within-subject design, healthy males received either single doses of aripiprazole and risperidone (n=28), amisulpride and lorazepam (n=30), or modafinil and valproate (n=30), and placebo. Prepulse inhibiton (PPI) and P50 suppression were assessed. Clinically associated symptoms were evaluated using the SCL-90-R. Aripiprazole, risperidone, and amisulpride increased P50 suppression in low P50 gaters. Lorazepam, modafinil, and valproate did not influence P50 suppression in low gaters. Furthermore, low P50 gaters scored significantly higher on the SCL-90-R than high P50 gaters. Aripiprazole increased PPI in low PPI gaters, whereas modafinil and lorazepam attenuated PPI in both groups. Risperidone, amisulpride, and valproate did not influence PPI. P50 suppression in low gaters appears to be an antipsychotic-sensitive neurophysiologic marker. This conclusion is supported by the association of low P50 suppression and higher clinically associated scores. Furthermore, PPI might be sensitive for atypical mechanisms of antipsychotic medication. The translational model investigating differential effects of AAPs on gating in healthy subjects with naturally low gating can be beneficial for phase II/III development plans by providing additional information for critical decision making.

Role of cerebellar dopamine D(3) receptors in modulating exploratory locomotion and cataleptogenicity in rats

Dopamine D(3) receptors are highly expressed in the cerebellum; however, their pathophysiological functions are not fully understood. Here, we conducted microinjection studies to clarify the role of cerebellar D(3) receptors in modulating locomotion and cataleptogenicity in rats. Microinjection of the preferential D(3) agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) into lobe 9 of the cerebellum significantly reduced spontaneous locomotor activity with a U-shaped dose-response curve. The intracerebellar microinjection of 7-OH-DPAT did not elicit catalepsy by itself, but markedly potentiated catalepsy induction with a low dose (0.3mg/kg) of haloperidol. The catalepsy enhancement by 7-OH-DPAT occurred in a dose-dependent manner and was not associated with the locomotor inhibition. U-99194A (a selective D(3) antagonist) or AD-6048 (a preferential D(3) vs. D(2) antagonist) antagonized both the catalepsy enhancement and the locomotor inhibition with 7-OH-DPAT. In addition, U-99194A and AD-6048 per se significantly alleviated catalepsy induced by a high dose (0.5mg/kg) of haloperidol. Furthermore, microinjection of 7-OH-DPAT into the nucleus accumbens or the dorsolateral striatum neither affected spontaneous locomotor activity nor haloperidol (0.3mg/kg)-induced catalepsy. The present results illustrate for the first time the role of cerebellar D(3) receptors in modulating cataleptogenicity of antipsychotic agents, implying that blockade of cerebellar D(3) receptors contributes to the reduction of extrapyramidal side effects.

Evaluation of the potential of antipsychotic agents to induce catalepsy in rats: assessment of a new, commercially available, semi-automated instrument

Haloperidol induced catalepsy was determined using the classic bar test and a new MED Associates Catalepsy Test Chamber instrument. The dose that produced an adverse effect in 50% of rats (AED50) for haloperidol was calculated using the instrument data as 0.29 mg/kg. Hand scoring of the video recordings gave AED50 values of 0.30 and 0.31 mg/kg, both well within the 95% CL of the instrument data. Clozapine was also evaluated and catalepsy was not detected up to 40 mg/kg. No significant difference was found between the instrument and hand scoring data. The instrument was useful for testing haloperidol and clozapine, relieving much of the tedium and variability experienced without its use. It was especially valuable at measuring shorter time periods, where the researcher cannot react as quickly. Finally, olanzapine was also evaluated. However, clenched forepaws and hind paws prevented the use of the instrument alone at higher doses. A backup stopwatch was used for the bar test in these cases. Some of the advantages and limitations are discussed. Results are also compared to the crossed-legs position (CLP) test for all three antipsychotics. While haloperidol gave similar results at all concentrations tested, clozapine deviated significantly at the highest dose (40 mg/kg) displaying catalepsy in the CLP test but not in the bar test. Olanzapine displayed catalepsy in rats significantly different from vehicle at 40 mg/kg in both the bar and CLP tests. However, the CLP test may be more suited to compounds with gripping problems which prevent the consistent grasping of the bar. Overall, the instrument was found to be a useful aid in conducting the bar test for catalepsy. The CLP test was found to complement the bar test under certain conditions and could provide additional data that might be missed by the bar test for compounds producing grasping problems.

Imaging brain gene expression profiles by antipsychotics: region-specific action of amisulpride on postsynaptic density transcripts compared to haloperidol

Induction of motor disorders is considered the clinical landmark differentiating typical from atypical antipsychotics, and has been mainly correlated to dopamine D2 receptors blockade in striatum. This view is challenged by benzamides, such as amisulpride, which display low liability for motor side effects despite being D2/D3 receptors high-affinity blocking agents. These effects have been explained with the prominent presynaptic action of amisulpride or with the fast dissociation at D2 receptors, but there is scarce information on the effects of amisulpride on postsynaptic signaling. We carried out a molecular imaging study of gene expression after acute administration of haloperidol (0.8 mg/kg), amisulpride (10 or 35 mg/kg), or vehicle, focusing on postsynaptic genes that are key regulators of synaptic plasticity, such as Arc, c-fos, Zif-268, Norbin, Homer. The last one has been associated to schizophrenia both in clinical and preclinical studies, and is differentially induced by antipsychotics with different D2 receptors affinity. Topography of gene expression revealed that amisulpride, unlike haloperidol, triggers transcripts expression peak in medial striatal regions. Correlation analysis of gene expression revealed a prevalent correlated gene induction within motor corticostriatal regions by haloperidol and a more balanced gene induction within limbic and motor corticostriatal regions by amisulpride. Despite the selective dopaminergic profile of both compounds, our results demonstrated a differential modulation of postsynaptic molecules by amisulpride and haloperidol, the former impacting preferentially medial regions of striatum whereas the latter inducing strong gene expression in lateral regions. Thus, we provided a possible molecular profile of amisulpride, putatively explaining its "atypical atypicality".

Effects of risperidone, amisulpride and nicotine on eye movement control and their modulation by schizotypy

RATIONALE

The increasing demand to develop more efficient compounds to treat cognitive impairments in schizophrenia has led to the development of experimental model systems. One such model system combines the study of surrogate populations expressing high levels of schizotypy with oculomotor biomarkers.

OBJECTIVES

We aimed (1) to replicate oculomotor deficits in a psychometric schizotypy sample and (2) to investigate whether the expected deficits can be remedied by compounds shown to ameliorate impairments in schizophrenia.

METHODS

In this randomized double-blind, placebo-controlled study 233 healthy participants performed prosaccade (PS), antisaccade (AS) and smooth pursuit eye movement (SPEM) tasks after being randomly assigned to one of four drug groups (nicotine, risperidone, amisulpride, placebo). Participants were classified into medium- and high-schizotypy groups based on their scores on the Schizotypal Personality Questionnaire (SPQ, Raine (Schizophr Bull 17:555-564, 1991)).

RESULTS

AS error rate showed a main effect of Drug (p < 0.01), with nicotine improving performance, and a Drug by Schizotypy interaction (p = 0.04), indicating higher error rates in medium schizotypes (p = 0.01) but not high schizotypes under risperidone compared to placebo. High schizotypes had higher error rates than medium schizotypes under placebo (p = 0.03). There was a main effect of Drug for saccadic peak velocity and SPEM velocity gain (both p ≤ 0.01) indicating impaired performance with risperidone.

CONCLUSIONS

We replicate the observation of AS impairments in high schizotypy under placebo and show that nicotine enhances performance irrespective of group status. Caution should be exerted in applying this model as no beneficial effects of antipsychotics were seen in high schizotypes.

The role of dopamine D(3) receptors in antipsychotic activity and cognitive functions

Dopamine D(3) receptors have a pre- and postsynaptic localization in brain stem nuclei, limbic parts of the striatum, and cortex. Their widespread influence on dopamine release, on dopaminergic function, and on several other neurotransmitters makes them attractive targets for therapeutic intervention. The signaling pathways of D(3) receptors are distinct from those of other members of the D(2)-like receptor family. There is increasing evidence that D(3) receptors can form heteromers with dopamine D(1), D(2), and probably other G-protein-coupled receptors. The functional consequences remain to be characterized in more detail but might open new interesting pharmacological insight and opportunities. In terms of behavioral function, D(3) receptors are involved in cognitive, social, and motor functions, as well as in filtering and sensitization processes. Although the role of D(3) receptor blockade for alleviating positive symptoms is still unsettled, selective D(3) receptor antagonism has therapeutic features for schizophrenia and beyond as demonstrated by several animal models: improved cognitive function, emotional processing, executive function, flexibility, and social behavior. D(3) receptor antagonism seems to contribute to atypicality of clinically used antipsychotics by reducing extrapyramidal motor symptoms; has no direct influence on prolactin release; and does not cause anhedonia, weight gain, or metabolic dysfunctions. Unfortunately, clinical data with new, selective D(3) antagonists are still incomplete; their cognitive effects have only been communicated in part. In vitro, virtually all clinically used antipsychotics are not D(2)-selective but also have affinity for D(3) receptors. The exact D(3) receptor occupancies achieved in patients, particularly in cortical areas, are largely unknown, mainly because only nonselective or agonist PET tracers are currently available. It is unlikely that a degree of D(3) receptor antagonism optimal for antipsychotic and cognitive function can be achieved with existing antipsychotics. Therefore, selective D(3) antagonism represents a promising mechanism still to be fully exploited for the treatment of schizophrenia, cognitive deficits in schizophrenia, and comorbid conditions such as substance abuse.

Variable maternal stress in rats alters locomotor activity, social behavior, and recognition memory in the adult offspring

Rats repeatedly exposed to variable prenatal stress (PNS) exhibit behavioral signs that are similar to those manifested in several neuropsychiatric disorders such as deficits in attention and inhibitory control, and impairments in memory-related task performance. The purpose of the study described here was to conduct a comprehensive battery of tests to further characterize the behavioral phenotype of PNS rats as well as to evaluate the sensitivity of the model to therapeutic interventions (i.e., to compounds previously shown to have therapeutic potential in neuropsychiatric disorders). The results of this study indicated that PNS in rats is associated with: 1) increased locomotor activity and stereotypic behaviors, 2) elevated sensitivity to the psychostimulant amphetamine, 3) increased aggressive behaviors toward both adult and juvenile rats and 4) delay-dependent deficits in recognition memory. There was no evidence that PNS rats exhibited deficits in other areas of motor function/learning, sensorimotor gating, spatial learning and memory, social withdrawal, or anhedonia. In addition, the results revealed that the second generation antipsychotic risperidone attenuated amphetamine-related increases in locomotor activity in PNS rats; however, the effect was not sustained over time. Furthermore, deficits in recognition memory in PNS rats were attenuated by the norepinephrine reuptake inhibitor, atomoxetine, but not by the α7 nicotinic acetylcholine receptor partial agonist, GTS-21. This study supports the supposition that important phenomenological similarities exist between rats exposed to PNS and patients afflicted with neuropsychiatric disorders thus further establishing the face validity of the model for evaluating potential therapeutic interventions.

Effects of amisulpride and aripiprazole on progressive-ratio schedule performance: comparison with clozapine and haloperidol

Clozapine and some other atypical antipsychotics (e.g. quetiapine, olanzapine) have been found to exert a characteristic profile of action on operant behaviour maintained by progressive-ratio schedules, as revealed by Killeen's Mathematical Principles of Reinforcement model of schedule-controlled behaviour. These drugs increase the value of a parameter that expresses the 'incentive value' of the reinforcer (a) and a parameter that is inversely related to the organism's 'motor capacity' (δ). This experiment examined the effects of two further atypical antipsychotics, aripiprazole and amisulpride, on progressive-ratio schedule performance in rats; the effects of clozapine and a conventional antipsychotic, haloperidol, were also examined. In agreement with previous findings, clozapine (4, 8 mg kg⁻¹) increased a and δ, whereas haloperidol (0.05, 0.1 mg kg⁻¹) reduced a and increased δ. Aripiprazole (3,30 mg kg⁻¹) increased δ but did not affect a. Amisulpride (5, 50 mg kg⁻¹) had a delayed and protracted effect: δ was increased 3-6 hours after treatment; a was increased 1.5 hours, and reduced 12-24 hours after treatment. Interpretation based on Killeen's model suggests that aripiprazole does not share clozapine's ability to enhance reinforcer value. Amisulpride produced a short-lived enhancement, followed by a long-lasting reduction, of reinforcer value. Both drugs impaired motor performance.

Evaluation of the behavioral and pharmacokinetic profile of SYA013, a homopiperazine analog of haloperidol in rats

SYA013, a homopiperazine analog of haloperidol, was further evaluated for antipsychotic potential using additional animal models. Previously, SYA013 was tested in mice with an antipsychotic screening model in which it inhibited apomorphine induced climbing behavior, indicating antagonism of the dopaminergic system and the potential for use in the treatment of schizophrenia. In this study, SYA013 was shown to inhibit both d-amphetamine-induced locomotor activity in rats and conditioned avoidance response (CAR) in rats in a dose dependent manner and in the case of CAR, without producing any escape failure responses (EFRs), two tests predictive of antipsychotic action. The selective 5HT(1A) antagonist WAY100,635 was used to determine if binding of SYA013 to the 5HT(1A) receptor contributed to suppression of CAR. The results indicated that 0.63mg/kg WAY100,635 did not have a significant effect on the inhibition of CAR by SYA013. Pharmacokinetic parameters in brain and plasma were determined for SYA013. A log brain/plasma concentration ratio at a t(max) of 1.48 suggests that SYA013 readily crosses the blood brain barrier (BBB). The hypothesis that binding of SYA013 to the 5HT(1A) receptor contributed to the lack of significant catalepsy was investigated using the 5HT(1A) antagonist WAY100,635. The results of acute and semi-chronic tests suggest that binding to the 5HT(1A) receptor alone did not significantly account for the lack of catalepsy. Lack of catalepsy was preserved after the semi-chronic challenge with SYA013. These tests further indicate that SYA013 has a pharmacological profile with the potential for use in the treatment of neuropsychiatric diseases. In addition, the 5HT(1A) receptor does not appear to play a significant role in the pharmacological profile of SYA013.

In vitro P-glycoprotein efflux inhibition by atypical antipsychotics is in vivo nicely reflected by pharmacodynamic but less by pharmacokinetic changes

BACKGROUND

P-glycoprotein (P-gp), an efflux transporter of the blood-brain barrier, limits the access of multiple xenobiotics to the central nervous system (CNS). Thus drug-dependent inhibition, induction or genetic variation of P-gp impacts drug therapy.

METHODS

We investigated atypical antipsychotics and their interaction with P-gp. Amisulpride, clozapine, N-desmethylclozapine, olanzapine, and quetiapine were assessed in vitro on their inhibitory potential and in vivo on their disposition in mouse serum and brain, and behaviourally on the RotaRod test. In vivo wildtype (WT) and mdr1a/1b double knockout mice (mdr1a/1b (-/-, -/-); KO) were investigated.

RESULTS

In rhodamine 123 efflux assay drugs inhibitory potency to P-gp could be ranked quetiapine>N-desmethylclozapine>clozapine>olanzapine. When treating WT and KO mice i.p. and assessing brain and serum levels by HPLC analysis, P-gp expression has the highest but a rather short effect on the distribution of amisulpride, whereas the others ranked N-desmethylclozapine>olanzapine>quetiapine>clozapine; contrasted by in vivo behavioral changes at various time points. Here quetiapine>clozapine>olanzapine impacts behavior most when P-gp is lacking. Present results indicate the relevance of P-gp expression for CNS-drug therapy.

CONCLUSIONS

Combination of in vitro, and in vivo methods highlights that inhibitory potency did not reflect P-gp related drug disposition. But, when drugs were ranked for inhibitory potency, this order is reflected in pharmacodynamic changes or vice versa. Pharmacodynamic effects otherwise were at most correlated to drug brain levels, which however, were present only to a limited extent (by positron emission tomography) accessible in humans.

Pharmacogenetics of response to antipsychotics in patients with schizophrenia

This review presents the findings of pharmacogenetic studies exploring the influence of gene variants on antipsychotic treatment response, in terms of both symptom improvement and adverse effects, in patients with schizophrenia. Despite numerous studies in the field, replicating findings across different cohorts that include subjects of different ethnic groups has been challenging. It is clear that non-genetic factors have an important contribution to antipsychotic treatment response. Differing clinical, demographic and environmental characteristics of the cohorts studied have added substantial complexity to the interpretation of the positive and negative findings of many studies. Pharmacogenomic genome-wide investigations are beginning to yield interesting data although they have failed to replicate the most robust findings of candidate gene studies, and are limited by the sample size, especially given the need for studying homogeneous cohorts. Most of the studies conducted on cohorts treated with single antipsychotics have investigated clozapine, olanzapine or risperidone response. These studies have provided some of the most replicated associations with treatment efficacy. Serotonergic system gene variants are significantly associated with the efficacy of clozapine and risperidone, but may have less influence on the efficacy of olanzapine. Dopamine D3 receptor polymorphisms have been more strongly associated with the efficacy of clozapine and olanzapine, and D2 genetic variants with the efficacy of risperidone. Serotonin influences the control of feeding behaviour and has been hypothesized to have a role in the development of antipsychotic-induced weight gain. Numerous studies have linked the serotonin receptor 2C (5-HT2C) -759-C/T polymorphism with weight gain. The leptin gene variant, -2548-G/A, has also been associated with weight gain in several studies. Pharmacogenetic studies support the role of cytochrome P450 enzymes and dopamine receptor variants in the development of antipsychotic-induced movement disorders, with a contribution of serotonergic receptors and other gene variants implicated in the mechanism of action of antipsychotics. Clozapine-induced agranulocytosis has been associated with polymorphisms in the major histocompatibility complex gene (HLA).

Partial agonists in schizophrenia--why some work and others do not: insights from preclinical animal models

While dopamine D2 receptor partial agonists (PAs) have been long considered for treating schizophrenia, only one, aripiprazole, is clinically available for therapeutic use. This raises critically important questions as to what is unique about aripiprazole and to what extent animal models can predict therapeutic success. A number of PAs whose clinical fate is known: aripiprazole, preclamol, terguride, OPC-4392 and bifeprunox were compared to haloperidol (a reference antipsychotic) in several convergent preclinical animal models; i.e. amphetamine-induced locomotion (AIL) and conditioned avoidance response (CAR), predictive of antipsychotic effects; unilateral nigrostriatal lesioned rats, a model of hypo-dopaminergia; striatal Fos induction, a molecular marker for antipsychotic activity; and side-effects common to this class of drugs: catalepsy (motor side-effects) and prolactaemia. The results were compared across drugs with reference to their measured striatal D2 receptor occupancy. All the PAs occupied striatal D2 receptors in a dose dependent manner, inhibited AIL and CAR, and lacked motor side-effects or prolactinaemia despite D2 receptor occupancy exceeding 80%. At comparative doses, aripiprazole distinguished itself from the other PAs by causing the least rotation in the hypo-dopaminergic model (indicating the least intrinsic activity) and showed the highest Fos expression in the nucleus accumbens (indicating functional D2 antagonism). Although a number of PAs are active in antipsychotic animal models, not all of them succeed. Given that only aripiprazole is clinically available, it can be inferred that low functional intrinsic activity coupled with sufficient functional antagonism as reflected in the animal models may be a marker of success.

Delayed-onset akathisia due to amisulpride

Despite the fact that second-generation antipsychotics have a lower potential to cause extrapyramidal side-effects, including akathisia, their incidence is not negligible. Recent work suggests that tardive akathisia may have pharmacological differences from acute akathisia. In the present study, we have evaluated the nature of delayed-onset akathisia in patients on amisülpride monotherapy. Overall, we screened 56 patients on amisulpride treatment for 2 months at a stabilized amisulpride dose. However, 18 patients with diagnostic and statistical manual of mental disorders-IV (DSM-IV) presented with acute or delayed-onset akathisia, and all of them also met the entry criteria. The patients were evaluated at baseline and at the time when akathisia presented clinically, with respect to the Positive and Negative Syndrome Scale and Barnes Akathisia Scale (BAS). Using the primary categorical criterion of akathisia (≥2 points of the BAS global scale), 12 (21.4%) of the 56 patients experienced delayed-onset akathisia, and six (10.7%) showed acute akathisia. The mean time for onset of acute or delayed-onset akathisia was 5.8 ± 2.1 and 39.4 ± 11.3 days, respectively. The mean BAS scores at baseline and after the period of 2 months were 1.3 ± 0.6 and 3.9 ± 2.4, respectively (P < 0.001). Our results revealed that amisulpride could considerably lead to delayed-onset akathisia. However, studies comprising larger samples receiving different antipsychotics, and more comprehensive assessment, will help to ascertain the role of amisulpride in delayed-onset akathisia.

The acute and chronic effects of combined antipsychotic-mood stabilizing treatment on the expression of cortical and striatal postsynaptic density genes

The detection of changes in postsynaptic gene expression after the administration of mood stabilizers, alone or in combination with antipsychotics, and antidepressants in animal models of drug treatment, may represent a valuable strategy to explore the molecular targets of the mainstay treatments for bipolar disorder. In this study we investigated, in both acute and chronic paradigms, the expression of specific postsynaptic density genes (Homer1a, Homer1b/c, and PSD95) and genes putatively implicated in mood stabilizers mechanism of action (GSK3b, ERK) after administration of first (haloperidol) or second generation antipsychotics (quetiapine 30 mg/kg), alone or in combination with valproate. Moreover, we compared the effects of an antidepressant agent widely used in bipolar depression (citalopram) with a low dose of quetiapine (15 mg/kg), which has been demonstrated to display antidepressant action in bipolar depression. In striatal regions, Homer1a expression was strongly induced by haloperidol compared to all the other treatments. Haloperidol plus valproate also markedly induced Homer1a, but to a significant lesser extent than haloperidol alone. Also in the chronic paradigm haloperidol, but not haloperidol plus valproate, induced Homer1a expression in all the subregions of the caudate-putamen and in the nucleus accumbens core. The high dose of quetiapine significantly induced Homer1a in anterior cingulated, premotor and motor subregions of the cortex, and the extent of induction was significantly higher as compared to the lower dose. Oppositely, Homer1a expression was decreased in the cortex by citalopram acute administration. ERK gene was upregulated in cortex and striatum by the acute treatment with valproate and with the combination of haloperidol or quetiapine plus valproate, whereas no significant differences were noticed in GSK3b expression among treatments. PSD95 showed a significant upregulation by acute citalopram and by haloperidol plus valproate in both cortical and subcortical regions. Haloperidol and quetiapine 30 mg/kg, oppositely, significantly reduced the expression of the gene in the cortex. In conclusion, these results suggest that the combined treatment with a typical or an atypical antipsychotic plus valproate may induce differential modulation of postsynaptic genes expression when compared to the effects of these drugs individually administered.

T-type calcium channel antagonism produces antipsychotic-like effects and reduces stimulant-induced glutamate release in the nucleus accumbens of rats

T-type calcium channels are important in burst firing and expressed in brain regions implicated in schizophrenia. Therefore, we examined the effects of novel selective T-type calcium channel antagonists in preclinical assays predictive of antipsychotic-like activity. TTA-A2 blocked the psychostimulant effects of amphetamine and MK-801 and decreased conditioned avoidance responding. These effects appeared mechanism based, rather than compound specific, as two structurally dissimilar T-type antagonists also reduced amphetamine-induced psychomotor activity. Importantly, the ability to reduce amphetamine's effects was maintained following 20 days pre-treatment with TTA-A2. To explore the neural substrates mediating the observed behavioral effects, we examined the influence of TTA-A2 on amphetamine-induced c-fos expression as well as basal and stimulant-evoked dopamine and glutamate release in the nucleus accumbens. TTA-A2 decreased amphetamine-induced c-fos expression as well as MK-801-induced, but not basal, glutamate levels in the nucleus accumbens. Basal, amphetamine- and MK-801-induced dopamine efflux was altered. These findings suggest that T-type calcium channel antagonism could represent a novel mechanism for treating schizophrenia.

Dose-related effects of clozapine and risperidone on the pattern of brain regional serotonin and dopamine metabolism and on tests related to extrapyramidal functions in rats

The present study was designed to evaluate the behavioral and neurochemical profiles of clozapine and risperidone in rats in a dose-dependent manner. Animals injected intraperitoneally (i.p.) with clozapine (2.5, 5.0 and 10.0 mg kg-1) or risperidone (1.0, 2.5 and 5.0 mg kg-1) were sacrificed 1 h later to collect brain samples. Hypolocomotive effects (home cage activity and catalepsy) were successively monitored in each animal after the drug or saline administration. Both drugs significantly (p < 0.01) decreased locomotor activity at high doses and in a dose-dependent manner. Maximum (100%) cataleptic potential was achieved at a high dose (5.0 mg kg-1) of risperidone. Neurochemical estimations were carried out by HPLC with electrochemical detection. Both drugs, at all doses, significantly (p < 0.01) increased the concentration of homovanillic acid (HVA), a metabolite of dopamine (DA), in the striatum. Dihydroxyphenylacetic acid (DOPAC) levels increased in the striatum and decreased in the rest of the brain, particularly in clozapine-injected rats. 5-Hydroxyindoleacetic acid (5-HIAA), the predominant metabolite of serotonin, significantly (p < 0.01) decreased in the striatum. 5-Hydroxytryptamine (5-HT) was significantly (p < 0.01) increased by risperidone and decreased by clozapine in the rest of the brain. Striatal tryptophan (TRP) was significantly (p < 0.01) decreased by risperidone and increased in the rest of the brain. The striatal HVA/DA ratio increased and the 5-HT turnover rate remained unchanged in the rest of the brain. Results suggest that the affinity of the two drugs towards D2/5-HT1A receptors interaction is involved in lower incidence of extrapyramidal side effects. Role of 5-HT1A receptors in the treatment of schizophrenia is discussed.

Haloperidol induces higher Homer1a expression than risperidone, olanzapine and sulpiride in striatal sub-regions

Homer1a and Yotiao are two post-synaptic density proteins at the crossroad of dopamine-glutamate neurotransmission. Homer1a has been implicated in the pathophysiology of schizophrenia and is differentially induced by typical and atypical antipsychotics, perhaps according to their dopaminergic profile. Yotiao has been involved in glutamate and dopamine post-synaptic signalling. Here, we seek to determine whether Homer1a and Yotiao might be implicated in post-synaptic response to antipsychotics with affinity to different dopamine D(2) receptors: haloperidol (0.8mg kg(-1)), risperidone (3mg kg(-1)), olanzapine (2.5mg kg(-1)) and (-)-sulpiride (50mg kg(-1)). Homer1a expression was significantly induced by haloperidol compared to vehicle and to atypical antipsychotics in almost all striatal sub-regions. Atypical antipsychotics induced the gene in the lateral putamen and in the core of the accumbens only. All antipsychotics, with the exclusion of sulpiride, elicited a dorsolateral-to-ventromedial distribution pattern of Homer1a expression. No significant induction was detected for Yotiao. These results suggest that the quantitative and topographical pattern of Homer1a expression may putatively be related to antipsychotics affinity and/or occupancy at dopamine D(2) receptors.

MK-801 produces a deficit in sucrose preference that is reversed by clozapine, D-serine, and the metabotropic glutamate 5 receptor positive allosteric modulator CDPPB: relevance to negative symptoms associated with schizophrenia?

Currently prescribed antipsychotics attenuate the positive symptoms of schizophrenia but fail or only mildly improve negative symptoms. The present study aimed to establish an animal model of negative symptoms by examining the effects of the NMDA receptor antagonist MK-801 on sucrose preference. We sought to validate the model by examining the effects of clozapine and D-serine, for which there are positive clinical data regarding their effects on negative symptoms, and haloperidol which is clinically ineffective. We extended our analysis by examining CDPPB, an mGlu5 receptor positive allosteric modulator. Acute MK-801 produced effects indicative of a shift in the hedonic experience of sucrose not confounded by disruptions in motor abilities or taste as revealed by: 1) a decrease in sucrose intake at low concentrations (0.8% or 1.2%), but no effect on water, 2) an increase in consumption for higher (7%) sucrose concentrations, reflecting a shift to the right in the concentration-consumption curve, and 3) no effect on quinine intake. Sub-chronic clozapine and acute d-serine attenuated the MK-801-induced deficit in 1.2% sucrose consumption, whereas sub-chronic haloperidol (0.02 mg/kg) did not. Finally, acute treatment with CDPPB also attenuated this deficit. These data suggest that this model may be useful for identifying novel agents that improve negative symptoms, and that compounds which enhance NMDA receptor function, such as mGlu5 receptor PAMs, may have clinical utility in this regard.

Central nervous system effects of the essential oil of the leaves of Alpinia zerumbet in mice

Objectives

Alpinia zerumbet, known in Brazil as colônia, is popularly used as a diuretic, antihypertensive, anti-ulcerogenic and sedative. Based on this, we have investigated the central effects of the essential oil isolated from A. zerumbet leaves.

Methods

Mice were treated once with 50 or 100 mg/kg of the essential oil, intraperitoneally, 30 min before being submitted to behavioural models of: locomotor activity (open-field), catalepsy, anxiety (elevated plus maze), depression (forced swimming test and tail suspension tests) as well as apomorphine-induced stereotypy.

Key findings

Results showed a dose-related decrease on locomotor activity and apomorphine-induced stereotypy. There was a decrease to the order of 55% of the grooming behaviour with both doses studied. The essential oil 100 mg/kg increased cataleptic activity (167%) and the immobility time in the forced swimming and tail suspension tests. Pretreatment with haloperidol (0.2 mg/kg, i.p.) alone also decreased locomotion, increased cataleptic activity and immobility time in the tail suspension test. No alterations in the elevated plus maze test were registered.

Conclusions

The essential oil of A. zerumbet leaves had depressant and possible antipsychotic activity, since it could reverse the stereotypy induced by apomorphine, presenting effects comparable with those obtained with haloperidol treatment.