D2 Partial Agonist Research Articles

Clinical challenges in the dosing and titration of cariprazine.

The introduction of a new psychopharmaceutical medication instead of the previous one always poses a certain challenge. In the case of antipsychotics (AP), these problems are considerably more complicated and are mainly caused by the question of dose equivalents, but also by the pharmacokinetic properties of the drug. In the case of partial dopamine D2 agonists, an additional issue is the possibility of deterioration when switching from the previous D2 antagonists to these drugs. Cross-titration is therefore generally recommended. Finally, due to the capsule form, it is not possible to increase the dose of cariprazine by less than 1.5 mg during titration. In this paper, we have presented our proposal to replace the most commonly used second-generation APs with the third-generation AP cariprazine. We have taken into account the dose equivalents, the pharmacological forms of the drugs and their pharmacokinetic and pharmacodynamic properties.

Brexpiprazole in patients with schizophrenia with or without substance use disorder: an observational study.

Partial dopamine D2 receptor agonists are used for psychotic symptoms in adults with schizophrenia spectrum disorders. Recently, interest surged for partial dopamine D2 receptor agonists in substance use disorders (SUDs). Since it is believed that SUDs decrease the efficacy of pharmacotherapy of underlying psychiatric disorders, we tested the efficacy of the partial D2 agonist brexpiprazole in patients with schizophrenia who were either comorbid with a SUD (SUD group) or not comorbid (non-SUD) to assess treatment response and the effect of brexpiprazole on substance craving in SUD. We included patients with DSM-5/DSM-5-TR schizophrenia (using SCID-5-CV) aged 18-66 years with either comorbid SUD or non-SUD to treat with brexpiprazole 4 mg/day for 6 months during February-October 2022. Patients were assessed with the Clinical Global Impressions-Severity (CGI-S) scale, the 24-item Brief Psychiatric Rating Scale (BPRS), and the Positive And Negative Syndrome Scale (PANSS) at baseline, weekly for the first 2 months and monthly for the next four. Furthermore, we assessed substance craving in SUD with a visual analog scale for craving (VAScrav) at the same timepoints. The total sample was 86 (85 analysable) 18- to 64-year-old (mean 39.32 ± 14.09) patients with schizophrenia [51 men (59.3%) and 35 women (40.7%)], of whom 48 SUD (55.8%) (37 men and 11 women) and 38 non-SUD (44.2%) (14 men and 24 women). No serious or persistent adverse events developed over the study period, but one patient dropped out for subjective akathisia. Results indicated the main effects of time with improvements over the course of the study for CGI-S, BPRS, and PANSS in both SUD and non-SUD groups and the entire sample, and for VAScrav in SUD. Brexpiprazole was associated with similar significant improvements in both groups at the 6 month endpoint compared to baseline. Treatment with brexpiprazole for 6 months improved psychotic symptoms in patients with schizophrenia, independently from whether they belonged to the SUD or the non-SUD group; hence, SUD comorbidity did not confer treatment resistance to brexpiprazole. Furthermore, in the SUD group, we observed reduced substance craving.

How sexuality is affected and managed in patients under antipsychotic drugs

IntroductionSexual dysfunction (SD) is a prevalent side effect of antipsychotic drugs (AP), and it impairs patients’ quality of life. Because of the distress caused by it, it should be borne in mind when prescribed since it is responsible for treatment nonadherence or discontinuation. SD affects about 45- 80% of males and 30-80% of females that take it. In SD, all phases of the sexual response cycle may be compromised.ObjectivesThis non-systematic review of the literature aims to better understand the antipsychotic-induced SD and its management to better compliance of AP-treated patients without compromising their quality of life.MethodsA semi-structured review on PubMed linking SD as a side effect of AP drugs.ResultsAll AP drugs can cause SD. It seems related to their mechanism of activity at receptors D2, 5-HT2, α1, H1, and M, which are also involved in sexual function. They do it by diminishing arousal, decreasing libido by blocking motivation and reward system and orgasm indirectly, provoking erectile dysfunction by vasodilatation, and decreasing woman lubrification. Hyperprolactinemia is a significant cause of sexual dysfunctions. Haloperidol, Risperidone, and Amisulpride (prolactin elevating AP) are more likely to cause SD than Olanzapine, Clozapine, Quetiapine, and Aripiprazole (prolactin sparing AP). Although psychotic disorders (Schizophrenia and other psychotic disorders) can impact sexual functioning, according to evidence, there is no denying the role of AP in this issue. Aripiprazole, a D2 partial agonist, has been associated with lower rates of SD and seems to reduce the rates of SD in patients previously treated with other AP. Other AP with the same potential dopamine agonist activity, such as Cariprazine and Brexpiprazole, can probably have the same effect. The management of SD induced by AP drugs should include measuring serum prolactin and modifying risk factors like hypertension, smoking, hyperglycemia, and hypercholesterolemia. In that regard, waiting for spontaneous remission, reducing the dose of the AP prescribed, or switching to Aripiprazole are all viable strategies, if possible. Although the evidence supporting the addition of symptomatic therapies is weak, adding dopaminergic drugs (amantadine, bromocriptine, cabergoline) or drugs with specific effects on sexual functioning (such as phosphodiesterase inhibitors or yohimbine) may be helpful in selected cases.ConclusionsAlthough all AP drugs can cause sexual dysfunction, it is difficult to determine its true prevalence accurately. AP-induced sexual dysfunction can adversely affect compliance and is one of the factors that must be considered when selecting treatment. In summarizing, Aripiprazole has shown to be the AP with the most favorable profile concerning SD. Cariprazine and Brexpiprazole, being also D2 partial agonists, may cause less SD.Disclosure of InterestNone Declared

Seventy Years of Treating Delusional Disorder with Antipsychotics: A Historical Perspective.

For many decades, delusional disorder (DD) has been considered a treatment-resistant disorder, with antipsychotics acknowledged as the best, though imperfect, treatment. It is possible that the discovery of the right drug could turn treatment resistance into treatment response. The goal of this narrative review is to provide a historical perspective of the treatment of DD since the introduction of antipsychotics 70 years ago. The following search terms were used to scan the literature: antipsychotics AND "delusional disorder". Findings were that therapy for DD symptoms has changed over time. Initial reports suggested that the drug of choice was the antipsychotic pimozide, and that this drug was especially effective for the somatic subtype of DD. Subsequent studies demonstrated that other antipsychotics, for instance, risperidone and olanzapine, were also highly effective. Treatment response may vary according to the presence or absence of specific symptoms, such as cognitive defect and depression. Clozapine, partial D2 agonists, and long-acting injectable drugs may be more effective than other drugs, but the evidence is not yet in. Because of the absence of robust evidence, treatment guidelines for the optimal management of DD are not yet available.

Atypical Antipsychotic Drugs in Dual Disorders: Current Evidence for Clinical Practice.

Concurrent disorder or dual diagnosis refers to a combination of substance use disorders and mental disorders that occur in the same patient simultaneously. These conditions pose significant clinical and healthcare impacts and are often underdiagnosed, undertreated, and complex to manage. We assessed the quality of current pharmacological recommendations for the management of dual diagnosis, particularly by evaluating the use of second-generation antipsychotics (SGA). A literature search was performed using the PubMed and Scopus databases for publications up to September 21, 2021, without any time restrictions. The following search strings were used: (aripiprazole OR brexpiprazole OR cariprazine OR paliperidone OR risperidone OR quetiapine OR clozapine OR olanzapine) AND (psychosis OR schizophrenia OR schizoaffective) AND ("substance use disorder" OR cocaine OR alcohol OR cannabis OR heroin OR "double diagnosis" OR "dual diagnosis")) NOT (animal OR rat OR mouse) NOT (review or meta-analysis). The search produced a final set of 41 articles. Most patients were males and were affected by schizophrenia, with cannabis the most abused substance, followed by alcohol. Aripiprazole was the most used drug, either orally or by long-acting formulations, followed by risperidone with oral and long-acting formulations, clozapine, olanzapine, and quetiapine. The findings highlight the use of SGA for the treatment of psychotic symptoms in comorbidity with substance use. Future studies on people with dual diagnosis and focused on long-term evaluations are warranted and need to investigate the efficacy of newly introduced molecules, such as partial D2 agonists and longacting injectable antipsychotics.

Relationship between subjective well-being and aripiprazole: an [11C]raclopride PET study

The dopamine blockade by antipsychotics trigger subjective dysphoria. Compared with D2 antagonists, aripiprazole, a D2 partial agonist, was expected to produce a different experience. Indeed, a previous study reported no relationship between the D2 receptor occupancy by aripiprazole and subjective dysphoria, while the D2 receptor occupancy by antagonists was associated with negative subjective experiences. This study revisited the relationship in patients treated with aripiprazole by using an inhibitory Emax model, which enables the individual drug-free binding potential and D2 receptor occupancy to be properly estimated. Eight patients with schizophrenia who have been clinically stable on aripiprazole were enrolled. Assessments including Positive and Negative Syndrome Scale (PANSS) and Subjective Well-being under Neuroleptics Scale (Kv-SWN) were administered. [11C]raclopride PET scan were conducted 2, 26, and 74 h after aripiprazole administration. Regression analysis showed a significant negative association between the D2 receptor occupancy by aripiprazole in the striatum and the Kv-SWN (R2 = 0.55, p = 0.036), but the PANSS total score was not associated with the Kv-SWN (R2 = 0.42, p = 0.080). The negative association between D2 receptor occupancy by aripiprazole and subjective well-being implies that clinicians should find the lowest effective doses of aripiprazole for clinically stable patients to improve their subjective experiences and clinical outcomes.

Structure-Functional Selectivity Relationship Studies on A-86929 Analogs and Small Aryl Fragments toward the Discovery of Biased Dopamine D1 Receptor Agonists.

Dopamine regulates normal functions such as movement, reinforcement learning, and cognition, and its dysfunction has been implicated in multiple psychiatric and neurological disorders. Dopamine acts through D1- (D1R and D5R) and D2-class (D2R, D3R, and D4R) receptors and activates both G protein- and β-arrestin-dependent signaling pathways. Current dopamine receptor-based therapies are used to ameliorate motor deficits in Parkinson's disease or as antipsychotic medications for schizophrenia. These drugs show efficacy for ameliorating only some symptoms caused by dopamine dysfunction and are plagued by debilitating side effects. Studies in primates and rodents have shown that shifting the balance of dopamine receptor signaling toward the arrestin pathway can be beneficial for inducing normal movement, while reducing motor side effects such as dyskinesias, and can be efficacious at enhancing cognitive function compared to balanced agonists. Several structure-activity relationship (SAR) studies have embarked on discovering β-arrestin-biased dopamine agonists, focused on D2 partial agonists, noncatechol D1 agonists, and mixed D1/D2R dopamine receptor agonists. Here, we describe an SAR study to identify novel D1R β-arrestin-biased ligands using A-86929, a high-affinity D1R catechol agonist, as a core scaffold to identify chemical motifs responsible for β-arrestin-biased activity at both D1 and D2Rs. Most of the A-86929 analogs screened were G protein-biased, but none of them were exclusively arrestin-biased. Additionally, various small-fragment molecular probes displayed weak bias toward the β-arrestin pathway. Continued in-depth SFSR (structure-functional selectivity relationship) studies informed by structure determination, molecular modeling, and mutagenesis studies will facilitate the discovery of potent and efficacious arrestin-biased dopamine receptor ligands.

Hipersexuality in aripiprazole treatment : A case report

IntroductionAripiprazole is an antipsychotic that differs from the group in that it is a partial agonist of the D2 receptor, being also a partial agonist of 5HT1A and an antagonist of 5HT2A.Most antipsychotics cause a decrease in libido, affecting both sexual desire and function. According to the literature, D2 partial agonists can cause the appearance of compulsive behaviors as an adverse effect in 6-24% of patients. Among these behaviors you can find hypersexuality. In most cases, it subsides when treatment is stopped. We describe the case of a patient with bipolar disorder who develops hypersexual behaviors following the aripiprazole treatment. This is a 61-year-old bipolar patient receiving valproate and risperidone. It requires hospital admission due to manic symptoms where dysfunctional tremor is observed. Change from risperidone to aripiprazole. Subsequently, hypersexual behaviors appear, increased libido, obsession with sexual activities (compulsive masturbation with TV programs, mobile applications, cartoons) as well as delusional ideas about “receiving sexual gazes” with no other maniac symptomps.ObjectivesTo determine the possibility that hypersexuality was induced by treatment with aripiprazole.MethodsThe appearance in the time line of hypersexuality after the change of treatment would be indicative of causality.ResultsAfter switching back to risperidone, compulsive sexual behaviors disappear but not the delusional idea of being the focus of sexual gazes by everyone.ConclusionsAlthough it is not a common adverse effect, hypersexuality is listed in the literature as a rare adverse effect.DisclosureNo significant relationships.

Treating Patients with Aripiprazol: A Safe Gamble?

IntroductionAripiprazole (ARI) is an atypical antipsychotic drug with D2 partial agonist properties, usually prescribed to treat mood disorders (major depression or bipolar disorder) and schizophrenic disorder (schizophrenia or schizoaffective disorder). Dopamine receptor agonists, as is ARI, have been implicated in some cases of impulse-control problems, such as gambling disorder (GD), increased spending, hypersexuality and compulsive eating.ObjectivesCurrently, it is hypothesized that aripiprazole may cause impulse-control problems because it can produce a hyperdopaminergic state in the mesolimbic pathway (reward system) through its predominant action on dopamine D3 receptors. We intend to do a non-systematic review of the scientific information regarding this subject.MethodsThe authors revised the published literature about this topic, selecting relevant articles, systematic reviews and case reports, with the topic words: “aripiprazol”, “gambling disorder” and “dopamine receptor” in scientific data base.ResultsOverall, a few cases of ARI-induced pathological gambling as well as ARI-induced hypersexuality have been reported. In one study it was verified that comorbid psychiatric and substance use disorders were common among those who have experienced GD or worsened GD after beginning ARI treatment. In another study, it was verified that the group of patients who reported this alleged side-effect were mostly young (mean age, 33.6 years), mostly men (88.2%) and most lived alone.ConclusionsAttributing to dopamine agonists the only factor that can explain the onset of GD is simplistic and dangerous. Many other potential risk factors, including individual vulnerability factors (temperament, genetics) as well as environmental factors, must be considered.DisclosureNo significant relationships.

P.0910 Glutamatergic Early Gene-based evaluation of functional connectivity within neural nodes at different dosages of the D2 partial agonist aripiprazole

P.0910 Glutamatergic Early Gene-based evaluation of functional connectivity within neural nodes at different dosages of the D2 partial agonist aripiprazole

Dopaminergic mechanisms underlying the expression of antipsychotic-induced dopamine supersensitivity in rats

Antipsychotic treatment can produce a dopamine-supersensitive state, potentiating the response to dopamine receptor stimulation. In both schizophrenia patients and rats, this is linked to tolerance to ongoing antipsychotic treatment. In rodents, dopamine supersensitivity is often confirmed by an exaggerated psychomotor response to d-amphetamine after discontinuation of antipsychotic exposure. Here we examined in rats the dopaminergic mechanisms mediating this enhanced behavioural response, as this could uncover pathophysiological processes underlying the expression of antipsychotic-evoked dopamine supersensitivity. Rats received 0.5 mg/kg/day haloperidol via osmotic minipump for 2 weeks, before treatment was discontinued. After cessation of antipsychotic treatment, rats showed a supersensitive psychomotor response to the D2 agonist quinpirole, but not to the D1 partial agonist SKF38393 or the dopamine reuptake blocker GBR12783. Furthermore, acute D1 receptor blockade (using SCH39166) decreased the exaggerated psychomotor response to d-amphetamine in haloperidol-pretreated rats, whereas acute D2 receptor blockade (using sulpiride) enhanced it. Thus, after discontinuation of antipsychotic treatment, D1- and D2-mediated transmission differentially modulate the expression of a supersensitive response to d-amphetamine. This supersensitive behavioural response was accompanied by enhanced GSK3β activity and suppressed ERK1/2 activity in the nucleus accumbens (but not caudate-putamen), suggesting increased mesolimbic D2 transmission. Finally, after discontinuing haloperidol treatment, neither increasing ventral midbrain dopamine impulse flow nor infusing d-amphetamine into the cerebral ventricles triggered the expression of already established dopamine supersensitivity, suggesting that peripheral effects are required. Thus, while dopamine receptor-mediated signalling regulates the expression of antipsychotic-evoked dopamine supersensitivity, a simple increase in central dopamine neurotransmission is insufficient to trigger this supersensitivity.

High dose antipsychotic polypharmacy and dopamine partial agonists - time to rethink guidelines?

Guidelines for the treatment of schizophrenia limit the use of antipsychotic agents to clinically-established maximum doses. This acknowledges both the absence of additional efficacy of dopamine D2 receptor antagonists above a receptor occupancy threshold, and the increases in side effects that can occur at higher doses. These limits restrict the dosing of combinations of antipsychotics as they do single agents; drugs sharing the major antipsychotic mechanism of D2 receptor antagonism will act additively in blocking these receptors.Several newer antipsychotic drugs, including aripiprazole and cariprazine, act as partial agonists at the D2 receptor site and avoid action at several other receptors, effects at which are responsible for some non-dopaminergic adverse effects. This pharmacology imparts different characteristics to the drugs resulting often in a more favourable side effect profile. Their partial agonism, along with high affinities for the D2 receptor, also means that these drugs given adjunctively may in part replace, rather than enhance, the D2 antagonism of other antipsychotic agents. This can result in an improvement in certain side effects without loss of antipsychotic efficacy.This article makes the case for distinguishing the D2 partial agonists from antagonists in defining maximum doses of combined treatments, which would increase the options available to the prescriber, emphasising that pharmacological mechanisms need to be understood in identifying optimal treatments for psychotic illness.

Antipsychotic Polypharmacy for the Management of Schizophrenia: Evidence and Recommendations.

Schizophrenia is a debilitating illness with a lifetime prevalence estimate of 0.6% and consists of symptoms from the positive, negative, and cognitive domains. Social support, therapy, psychoeducation, and overall case management are very important aspects of the treatment of schizophrenia. However, as abnormalities in neurotransmission are one of the key findings of schizophrenia pathology, pharmacotherapies are cornerstones of the management of schizophrenia. Antipsychotics have been used as the primary pharmacological treatment of schizophrenia. These agents often have a good effect on reducing positive symptoms, but may not markedly improve negative symptoms or cognitive defects. However, at least 20% of individuals with schizophrenia do not experience a substantial response from monotherapy with antipsychotics. Further, despite evolving treatment protocols and advances in early recognition of the disorder, 70% of patients with schizophrenia require long-term, even lifetime, medication to control their symptoms and do not achieve complete recovery. To address these shortcomings, clinicians and research scientists have explored different combinations of treatments, polypharmacy, to improve the treatment of patients. Antipsychotic polypharmacy has been shown to cause more side effects than monotherapy, which is the main reason why most treatment guidelines caution against it. Antipsychotic monotherapy should be strived for and clozapine should be tried at the latest if two monotherapy trials with other antipsychotics have failed and no absolute contraindications exist. If residual symptoms exist despite trials of adequate dose and duration, other reasons that may reduce treatment effect should be ruled out. Long-acting injectables or blood concentration measurements should be considered to affirm compliance and proper serum levels. Antipsychotic polypharmacy should be considered and discussed with patients from whom the aforementioned procedures do not produce a satisfactory treatment result. In some cases, antipsychotic polypharmacy may produce better results than other forms of treatment augmentation, such as benzodiazepines. In particular, combining aripiprazole with clozapine may be effective in reducing treatment side effects or residual symptoms, and this is likely to hold true for combining other partial dopamine D2 agonists with clozapine as well, although currently scant data exist. More research is needed, both in controlled but also real-world settings, to define optimal antipsychotic polypharmacy and/or other psychotropic treatment augmentation strategies for specific patient groups and situations.

Current Neuropharmacological Interventions in Autism: Potential Drug Targets from Pre-clinical and Clinical Findings

Autism spectrum disorder is the term used in the most recent edition of the diagnostic and statistical manual of neurodevelopmental disorders, which includes conditions such as autism. Etiological factors such as environmental toxins, food, genes, bacterial infections, and viruses are the reasons behind autism. In the lack of diagnostic criteria, early studies of the disorder reported differences in motor and cognitive abilities in persons with autism. Autism neuropathological features are correlated with different brain areas, such as the cerebral cortex, amygdala, and hippocampus. Autism is associated with mitochondrial dysfunction, oxidative stress, neuroinflammatory reactions, neuroexcitation, and abnormal synapse formation. Pre-clinically, the administration of propionic acid in the brains of rats by stereotaxic technique exacerbates autistic behavioral and neurochemical alterations. Prescription drugs to alleviate neurological disorders for autism are risperidone (Blocks D2 and 5HT2A receptors) and aripiprazole (D2 and 5HT1A partial agonist) approved by the US-FDA, which comes with limited therapeutic intervention. Findings suggest that malfunctions of propionic acid-disrupted neuronal mitochondrial coenzyme Q10 (CoQ10) and etc-complexes are the most pathogenic events for autism. As a result, the current review focused on the history of disease, clinical and pre-clinical drugs under investigation and suggested mediating neuroprotective intervention in autism with mitochondrial CoQ10 activation. Additionally, a greater understanding of the mitochondrial signaling pathway is an effort to improve successful treatment not only for Autism but also for other neurological disorders.

Cannabidiol in Fragile X Syndrome (FXS): Proposed Mechanism of Action (MOA) Translates Into Meaningful Clinical Benefits [CONNECT-FX (ZYN2-CL-016)

Disruption in the endocannabinoid system in FXS is associated with social anxiety and irritability. Cannabidiol (CBD) acts as a negative allosteric modulator at presynaptic CB1 receptors, a 5HT1A agonist and a D2 partial agonist. FXS causes intellectual disability, making symptom recognition and self-report problematic. Therapeutic response must rely on objective description of change. ZYN002 is pharmaceutically manufactured transdermal CBD.

Effect of Switching to Brexpiprazole on Plasma Homovanillic Acid Levels and Antipsychotic-Related Side Effects in Patients with Schizophrenia or Schizoaffective Disorder.

ObjectiveAlthough switching antipsychotics is a common strategy in the treatment of schizophrenia, caution is needed because of the risk of worsening of psychosis, particularly when switching to a dopamine D2 partial agonist. Homovanillic acid (HVA), a dopamine metabolite, is thought to be a possible indicator of the response to antipsychotics. We examined the effects of switching to brexpiprazole monotherapy from other antipsychotics on plasma HVA levels and side effects during maintenance treatment of schizophrenia.MethodsThe antipsychotics of 37 Japanese patients with schizophrenia or schizoaffective disorder were switched to brexpiprazole for the improvement of side effects. We evaluated clinical symptoms and extrapyramidal symptoms (EPS) and took fasting blood samples at baseline and endpoint (eight weeks after completing the switch) to measure plasma levels of HVA, prolactin, and metabolic parameters.ResultsSwitching to brexpiprazole significantly decreased the Drug-Induced Extrapyramidal Symptoms Scale total score (p=0.008), prolactin levels (p<0.001), body weight (p=0.046), and body-mass index (p=0.034), and increased HDL cholesterol (p=0.008). On the other hand, switching to brexpiprazole did not change plasma levels of HVA or Positive and Negative Syndrome Scale scores.ConclusionSwitching to brexpiprazole significantly improved EPS, high prolactin levels, and metabolic side effects without elevating plasma HVA levels. Brexpiprazole may stabilize dopaminergic neural transmission and could be a useful strategy to decrease the burden in patients with schizophrenia during the maintenance phase. Because of the small sample size, further studies with larger sample sizes are needed to confirm and extend our results.

(±)VK4‐40, a novel dopamine D3 receptor partial agonist, attenuates cocaine reward and relapse in rodents

Despite widespread abuse of cocaine, there are no approved treatments for cocaine use disorder. Chronic cocaine use is associated with up-regulated dopamine D3 receptor expression in the brain. Therefore, most D3 -based medication development has focused on D3 antagonists. However, D3 antagonists do not attenuate cocaine intake under "easy" self-administration conditions, when response requirements are low. We evaluated a novel, highly selective and metabolically stable D3 partial agonist, (±)VK4-40, for its efficacy in reducing cocaine intake and relapse to drug seeking. The impact of (±)VK4-40 on cocaine intake and relapse was evaluated using intravenous self-administration procedures under a fixed-ratio 2 reinforcement schedule and cocaine-primed reinstatement conditions in rats. Optogenetic brain-stimulation reward procedures were used to evaluate the interaction of (±)VK4-40 and cocaine in the mesolimbic dopamine system in mice. Sucrose self-administration in rats and a conditioned place preference paradigm in mice were used to evaluate the abuse potential of (±)VK4-40 alone and other unwanted effects. (±)VK4-40 dose-dependently reduced cocaine self-administration and cocaine-primed reinstatement of drug-seeking behaviour. (±)VK4-40 also inhibited cocaine-enhanced brain-stimulation reward caused by optogenetic stimulation of dopamine neurons in the ventral tegmental area. (±)VK4-40 alone decreased brain-stimulation reward but produced neither conditioned place preference nor place aversion. This new D3 partial agonist also failed to alter oral sucrose self-administration. The novel D3 partial agonist, (±)VK4-40 attenuates cocaine reward and relapse in rodents, without significant unwanted effects. These findings support further investigation of D3 partial agonists as putative treatments for cocaine use disorder.

Lurasidone – pharmacodynamic and pharmacokinetic properties, clinical potential and interaction risk

Lurasidone is a novel second-generation antipsychotic approved for the treatment of schizophrenia and bipolar depression in adults. It displays high affinity for D2 and 5-HT2A and 5-HT7 receptors, moderate affinity for 5-HT1A and α2C-noradrenergic receptors, and negligible affinity for histamine H1 and muscarinic M1 receptors. It acts as potent D2, 5-HT2A and 5-HT7 antagonist and partial 5-HT1A agonist. Lurasidone taken orally is rapidly absorbed with the time to maximum concentration of 1-3 hours. Lurasidone should be taken with food (at least 350 kcal) due to limited absorption. The mean elimination half-life of lurasidone is 18.1–25.5 hours for doses 20–80 mg/day and 28.8–37.4 hours for doses of 120–160 mg/day. Steady-state is reached within 7 days. The drug is metabolised via CYP 3A4 and excreted mainly in faeces (67–80%) and with urine (about 8–19%). The use of lurasidone with strong inhibitors or inducers of CYP 3A4 (e.g. ketoconazole, erythromycin, or carbamazepine, respectively) is contraindicated. In the case of combined treatment of lurasidone and moderate inhibitors of CYP 3A4, the dose of lurasidone should be decreased to 40 mg/day. Lurasidone is an inhibitor of P-glycoprotein and could increase the level of digoxin and potentate the side effects risk of this drug. Pomelo, grapefruit, or a large amount of oranges should be avoided in the diet during treatment with lurasidone. Pharmacodynamic properties of lurasidone underlie its antipsychotic, antidepressant, precognitive, and sleep-awake rhythm normalising activity.

(-)-Stepholidine blocks expression, but not development, of cocaine conditioned place preference in rats

The purpose of this study was to investigate the effects of (-)-stepholidine (SPD), a compound with dopamine D1 partial agonist and D2/D3 antagonist properties, on the development and expression of cocaine conditioned place preference (CPP). Subjects (N = 65; male Long Evans rats) were tested using a CPP procedure consisting of 3 phases: (1) a 15-min pre-exposure session where animals could explore each compartment freely, (2) eight 30-min conditioning sessions where animals were restricted to one side or the other with cocaine (10 mg/kg) or saline, respectively, on alternating days and (3) a 15-minute preference test session where animals could explore each compartment freely. To test the effects of SPD on expression of cocaine CPP, rats were administered vehicle (distilled water with 20 % DMSO), 10, 15 or 20 mg/kg SPD (intraperitoneally) 30 min prior to the test session. We found that 20 mg/kg of SPD significantly blocked the expression of cocaine CPP. To test the effects of SPD on the development of CPP, 0 (vehicle), 10, 15 or 20mg/kg SPD were administered 30 min prior to each cocaine conditioning session and vehicle before each saline conditioning session; no treatment was given prior to the test session. A preference test showed that each SPD group maintained a CPP similar to the vehicle group. These data indicate that SPD can block the expression of a cocaine CPP but has no effect on its development, suggesting that it inhibits the effects of cocaine cues on cocaine incentive motivated behavior. These results suggest that SPD may be a potential treatment for cue-driven aspects of cocaine use disorder.

M143. REGIONAL CEREBRAL BLOOD FLOW IN INITIALLY ANTIPSYCHOTIC-NAïVE PATIENTS WITH SCHIZOPHRENIA OR PSYCHOSIS: EFFECTS OF PARTIAL D2 RECEPTOR AGONISM AND ASSOCIATION WITH SYMPTOM IMPROVEMENT

BackgroundSchizophrenia is suggested to stem from dysfunction of cortico-striato-thalamo-cortical networks. Supporting this, we have recently found increased glutamate levels in thalamus in antipsychotic-naïve patients with schizophrenia or psychosis. Moreover, higher baseline glutamate levels were related to less improvement of psychotic symptoms after treatment. Other groups have reported that striatal dopaminergic function in patients with psychosis is increased and associated with psychotic symptoms. Regional cerebral blood flow (rCBF) is considered a marker of neuronal activity and can be used to study the cortico-striato-thalamo-cortical networks.Here, we investigated rCBF in a large group of initially antipsychotic-naïve patients with schizophrenia or psychosis before and after treatment and related the findings to changes in psychotic symptoms.MethodsrCBF was acquired in 49 initially antipsychotic-naïve patients and 50 matched healthy controls at baseline, and in 32 patients and 53 healthy controls after 6 weeks with the pseudo-Continuous Arterial Spin Labelling (pCASL) sequence. Patients were treated with a partial dopamine D2 receptor agonist (aripiprazole) as monotherapy (mean dose: 10.6±5.4mg).Primary regions of interest of rCBF were thalamus, limbic- and associative striatum. In explorative analyses, we estimated rCBF in sensorimotor striatum, hippocampus-amygdala, and frontal lobe.Psychopathology was assessed with the positive and negative syndrome scale (PANSS).A linear mixed model was used to test if the change in rCBF was different in patients compared with healthy controls (significant interaction) with adjustment for age, sex, and whole brain rCBF. Post hoc tests evaluated possible group differences at baseline and after 6 weeks.In a general linear model, we investigated associations between baseline rCBF in striatum and thalamus and improvement in psychotic symptoms.ResultsrCBF changed over 6 weeks in all striatal regions (associative striatum: p=0.023; limbic striatum: p=0.004; sensorimotor striatum: p=0.004). Post hoc tests of associative striatum indicated no baseline group differences in rCBF (SCZ/HC: 63.4/65.1 mL/100g/min, p=0.59), however rCBF was higher in patients after 6 weeks (SCZ/HC: 68.8/63.2 mL/100g/min, p=0.049). Post hoc tests of limbic striatum indicated no baseline group differences in rCBF (SCZ/HC: 62.7/65.3 mL/100g/min, p=0.25) and no group differences rCBF after 6 weeks (SCZ/HC: 69.3/63.3 mL/100g/min, p=0.12).Post hoc tests of sensorimotor striatum indicated no baseline group differences in rCBF (SCZ/HC: 72.6/71.2 mL/100g/min, p=0.18), however, rCBF was significantly higher in patients after 6 weeks (SCZ/HC: 80.0/67.2 mL/100g/min, p<0.001).There were no group differences in the rCBF changes in thalamus (p=0.09), hippocampus-amygdala (p=0.24), frontal lobe (p=0.90), and the whole brain (p=0.14).In patients, higher baseline rCBF in limbic striatum was associated with less improvement in PANSS positive symptoms (p=0.025). We found no other associations between rCBF and psychopathy.DiscussionThe findings suggest that treatment with a partial dopamine D2 agonist increases rCBF in associative and sensorimotor striatum in initially antipsychotic-naïve patients and that higher rCBF in limbic striatum at baseline is related to poorer treatment outcome. Future studies should investigate the associations between different neurotransmitters and rCBF in vivo. This could further characterize disturbances in cortico-striato-thalamo-cortical networks in schizophrenia or psychosis as well as the effect of treatment.