Involvement of DA D3 Receptors in Structural Neuroplasticity of Selected Limbic Brain Circuits: Possible Role in Treatment-Resistant Depression.

Structural neuroplasticity in the adult brain is a process involving quantitative changes of the number and size of neurons and of their dendritic arborization, axon branching, spines, and synapses. These changes can occur in specific neural circuits as adaptive response to environmental challenges, exposure to stressors, tissue damage or degeneration. Converging studies point to evidence of structural plasticity in circuits operated by glutamate, GABA, dopamine, and serotonin neurotransmitters, in concert with neurotrophic factors such as Brain Derived Neurotrophic Factor (BDNF) or Insulin Growth Factor 1 (IGF1) and a series of modulators that include circulating hormones. Intriguingly, most of these endogenous agents trigger the activation of the PI3K/Akt/mTOR and ERK1/2 intracellular pathways that, in turn, lead to the production of growth-related structural changes, enhancing protein synthesis, metabolic enzyme functions, mitogenesis for energy, and new lipid-bilayer membrane apposition. The dopamine (DA) D3 receptor has been shown to play a specific role by inducing structural plasticity of the DAergic neurons of the nigrostriatal and mesocorticolimbic circuit, where they are expressed in rodents and humans, via activation of the mTORC1 and ERK1/2 pathways. These effects are BDNF-dependent and require the recruitment of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors to allow the structural changes. Since in mood disorders, depression and anhedonia have been proposed to be associated with impaired neuroplasticity and reduced DAergic tone in brain circuits connecting prefrontal cortex, ventral striatum, amygdala, and ventral mesencephalon, activation of D3 receptors could provide a therapeutic benefit. Sustained improvements of mood and anhedonia were observed in subjects with an unsatisfactory response to serotonin uptake inhibitors (SSRI) when treated with D3-preferential D2/D3 agonists such as pramipexole and ropinirole. The recent evidence that downstream mTOR pathway activation in human mesencephalic DA neurons is also produced by ketamine, probably the most effective antidepressant currently used in subjects with treatment-resistant depression, further supports the rationale for a D3 receptor activation in mood disorders.

Spike mutation resilient scFv76 antibody counteracts SARS-CoV-2 lung damage upon aerosol delivery.

The uneven worldwide vaccination coverage against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and emergence of variants escaping immunity call for broadly effective and easily deployable therapeutic agents. We have previously described the human single-chain scFv76 antibody, which recognizes SARS-CoV-2 Alpha, Beta, Gamma and Delta variants. We now show that scFv76 also neutralizes the infectivity and fusogenic activity of the Omicron BA.1 and BA.2 variants. Cryoelectron microscopy (cryo-EM) analysis reveals that scFv76 binds to a well-conserved SARS-CoV-2 spike epitope, providing the structural basis for its broad-spectrum activity. We demonstrate that nebulized scFv76 has therapeutic efficacy in a severe hACE2 transgenic mouse model of coronavirus disease 2019 (COVID-19) pneumonia, as shown by body weight and pulmonary viral load data. Counteraction of infection correlates with inhibition of lung inflammation, as observed by histopathology and expression of inflammatory cytokines and chemokines. Biomarkers of pulmonary endothelial damage were also significantly reduced in scFv76-treated mice. The results support use of nebulized scFv76 for COVID-19 induced by any SARS-CoV-2 variants that have emerged so far.

Synergic action of L-acetylcarnitine and L-methylfolate in Mouse Models of Stress-Related Disorders and Human iPSC-Derived Dopaminergic Neurons.

The epigenetic agents, L-acetylcarnitine (LAC) and L-methylfolate (MF) are putative candidates as add-on drugs in depression. We evaluated the effect of a combined treatment with LAC and MF in two different paradigms of chronic stress in mice and in human inducible pluripotent stem cells (hiPSCs) differentiated into dopaminergic neurons. Two groups of mice were exposed to chronic unpredictable stress (CUS) for 28 days or chronic restraint stress (CRS) for 21 day, and LAC (30 or 100 mg/kg) and/or MF (0.75 or 3 mg/kg) were administered i.p. once a day for 14 days, starting from the last week of stress. In both stress paradigms, LAC and MF acted synergistically in reducing the immobility time in the forced swim test and enhancing BDNF protein levels in the frontal cortex and hippocampus. In addition, LAC and MF acted synergistically in enhancing type-2 metabotropic glutamate receptor (mGlu2) protein levels in the hippocampus of mice exposed to CRS. Interestingly, CRS mice treated with MF showed an up-regulation of NFκB p65, which is a substrate for LAC-induced acetylation. We could also demonstrate a synergism between LAC and MF in cultured hiPSCs differentiated into dopamine neurons, by measuring dendrite length and number, and area of the cell soma after 3 days of drug exposure. These findings support the combined use of LAC and MF in the treatment of MDD and other stress-related disorders.

L-Acetylcarnitine causes analgesia in mice modeling Fabry disease by up-regulating type-2 metabotropic glutamate receptors.

Fabry disease (FD) is a X-linked lysosomal storage disorder caused by deficient function of the alpha-galactosidase A (α-GalA) enzyme. α-GalA deficiency leads to multisystemic clinical manifestations caused by the preferential accumulation of globotriaosylceramide (Gb3). A hallmark symptom of FD patients is neuropathic pain that appears in the early stage of the disease as a result of peripheral small fiber damage. Previous studies have shown that Acetyl-L-carnitine (ALC) has neuroprotective, neurotrophic, and analgesic activity in animal models of neuropathic pain. To study the action of ALC on neuropathic pain associated with FD, we treated α-GalA gene null mice (α-GalA(-/0)) with ALC for 30 days. In α-Gal KO mice, ALC treatment induced acute and long-lasting analgesia, which persisted 1 month after drug withdrawal. This effect was antagonized by single administration of LY341495, an orthosteric antagonist of mGlu2/3 metabotropic glutamate receptors. We also found an up-regulation of mGlu2 receptors in cultured DRG neurons isolated from 30-day ALC-treated α-GalA KO mice. However, the up-regulation of mGlu2 receptors was no longer present in DRG neurons isolated 30 days after the end of treatment. Taken together, these findings suggest that ALC induces analgesia in an animal model of FD by up-regulating mGlu2 receptors, and that analgesia is maintained by additional mechanisms after ALC withdrawal. ALC might represent a valuable pharmacological strategy to reduce pain in FD patients.

Probiotics-Containing Mucoadhesive Gel for Targeting the Dysbiosis Associated with Periodontal Diseases.

Objective: Periodontitis is a common disorder that leads to the loss of both tooth and personal well-being, contributing to worsen the risk for metabolic and cardiovascular diseases. Recently, probiotics, characterized by rapid oral dispersion, have been topically used. Here, we present data of a mucoadhesive gel containing probiotics, capable of ensuring a slow release of bacteria to prevent and treat periodontitis. Methods: An original mucoadhesive gel (AL0005) that is anhydrous and of food grade, loaded with the blend of lactobacilli and plants' dry extracts, has been assayed. Results: The release kinetics of the bacterial mixture in different experimental models in vitro, including simulated saliva or physiological solutions, showed a significant and stable release for 5-8 hours. In one in vivo study of a mouse model of periodontitis, a locally applied mucoadhesive gel enriched with probiotic strains improved significantly the tissue pathology when compared with vehicle-exposed mice. Conclusions: Together, the results suggest that this mucoadhesive gel can be useful in the normalization of the gum bacterial flora and improvement of the tissue pathology of gum disorders.

Social withdrawal and neurocognitive correlates in schizophrenia.

Poor neurocognitive performance has been associated with poor functional outcome in schizophrenia (SCZ) in past studies. Nonetheless, the likely association between neurocognition and social withdrawal has never been investigated. The aim of our study was to investigate in a large and heterogeneous sample of SCZ patient cross-sectional associations between neurocognitive domains and social withdrawal. The sample included 761 SCZ patients who completed the baseline visit in the CATIE study. Neurocognition was assessed by a comprehensive battery of tests resulting in five domain scores and a composite score. Social withdrawal was measured by a specific item of the Heinrichs-Carpenter Quality of Life Scale. Social withdrawal was associated with a lower score in the neurocognitive composite score and in 'Verbal memory,' 'Processing speed' and 'Working memory' scores. 'Verbal memory' score showed the strongest association with social withdrawal. Eight percent of the total variance of social withdrawal was explained by these three cognitive domains and additional clinical and sociodemographic factors (education years, PANSS positive symptoms score, and employment). Our results confirmed the wide heterogeneity and specificity of the correlation between neurocognitive domains and indicators of functional outcome in SCZ, underlining the role of certain neurocognitive abilities in social withdrawal.

Human inhalable antibody fragments neutralizing SARS-CoV-2 variants for COVID-19 therapy.

As of December 2021, coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a global emergency, and novel therapeutics are urgently needed. Here we describe human single-chain variable fragment (scFv) antibodies (76clAbs) that block an epitope of the SARS-CoV-2 spike protein essential for ACE2-mediated entry into cells. 76clAbs neutralize the Delta variant and other variants being monitored (VBMs) and inhibit spike-mediated pulmonary cell-cell fusion, a critical feature of COVID-19 pathology. In two independent animal models, intranasal administration counteracted the infection. Because of their high efficiency, remarkable stability, resilience to nebulization, and low cost of production, 76clAbs may become a relevant tool for rapid, self-administrable early intervention in SARS-CoV-2-infected subjects independently of their immune status.

Pharmacokinetics, pharmacodynamics and safety assessment of multiple doses of soticlestat in healthy volunteers.

AIMS: Soticlestat, a first-in-class inhibitor of cholesterol 24-hydroxylase (also known as cytochrome P450 46A1), is currently in development for the treatment of developmental and epileptic encephalopathies. Here, we report safety, tolerability, pharmacokinetic and pharmacodynamic outcomes from a phase I, randomized, double-blind, placebo-controlled, multiple-rising-dose study of soticlestat in healthy adults. METHODS: Five cohorts of healthy subjects (n = 8 each, randomized 6:2 soticlestat:placebo) received oral soticlestat 100-600 mg once daily (QD) or 300 mg twice daily (BID) for 10-14 days. Serial blood and urine samples were obtained on days 1, 7 (blood only) and 14. RESULTS: Soticlestat in the dose range 100-400 mg/day for up to 14 days was generally well tolerated. In total, 45 treatment-emergent adverse events (TEAEs) were reported; most (91%) were transient and mild in intensity. Two subjects experienced TEAEs leading to discontinuation: one receiving soticlestat 600 mg QD reported a severe event of acute psychosis; another receiving 300 mg BID reported a mild event of confusional state. Steady-state exposure to soticlestat increased in a slightly greater than dose-proportional manner across the dose range 100-400 mg QD. Peak plasma concentrations were reached within 0.33-0.5 hour, and soticlestat elimination half-life was approximately 4 hours. Renal excretion of soticlestat was negligible. Soticlestat 100-400 mg QD reduced 24S-hydroxycholesterol levels by 46.8 (coefficient of variation [CV%] -9.2) to -62.7% (CV% -7.3) at steady state; values of enzymatic inhibition were compatible with antiepileptic effects observed in preclinical models. CONCLUSION: The pharmacokinetic and pharmacodynamic profiles of soticlestat characterized here provided a data-driven rationale for clinical trial dose selection.

The Relationship Between Endoscopic and Clinical Recurrence in Postoperative Crohn's Disease: A Systematic Review and Meta-analysis.

BACKGROUND AND AIMS: We aimed to quantify the magnitude of the association between endoscopic recurrence and clinical recurrence [symptom relapse] in patients with postoperative Crohn's disease. METHODS: Databases were searched to October 2, 2020, for randomised controlled trials [RCTs] and cohort studies of adult patients with Crohn's disease with ileocolonic resection and anastomosis. Summary effect estimates for the association between clinical recurrence and endoscopic recurrence were quantified by risk ratios [RR] and 95% confidence intervals [95% CI]. Mixed-effects meta-regression evaluated the role of confounders. Spearman correlation coefficients were calculated to assess the relationship between these outcomes as endpoints in RCTs. An exploratory mixed-effects meta-regression model with the logit of the rate of clinical recurrence as the outcome and the rate of endoscopic recurrence as a predictor was also evaluated. RESULTS: In all, 37 studies [N = 4053] were included. For eight RCTs with available data, the RR for clinical recurrence for patients who experienced endoscopic recurrence was 10.77 [95% CI 4.08 to 28.40; GRADE moderate certainty evidence]; the corresponding estimate from 11 cohort studies was 21.33 [95% CI 9.55 to 47.66; GRADE low certainty evidence]. A single cohort study showed a linear relationship between Rutgeerts score and clinical recurrence risk. There was a strong correlation between endoscopic recurrence and clinical recurrence treatment effect estimates as trial outcomes [weighted Spearman correlation coefficient 0.51]. CONCLUSIONS: The associations between endoscopic recurrence and subsequent clinical recurrence lend support to the choice of endoscopic recurrence to monitor postoperative disease activity and as a primary endpoint in clinical trials of postoperative Crohn's disease.

Corrigendum: Negative Symptoms of Schizophrenia and Dopaminergic Transmission: Translational Models and Perspectives Opened by iPSC Techniques.

[This corrects the article DOI: 10.3389/fnins.2020.00632.].

Longitudinal study based on a safety registry for malaria patients treated with artenimol-piperaquine in six European countries.

BACKGROUND: European travellers to endemic countries are at risk of malaria and may be affected by a different range of co-morbidities than natives of endemic regions. The safety profile, especially cardiac issues, of artenimol (previously dihydroartemisinin)-piperaquine (APQ) Eurartesim® during treatment of uncomplicated imported falciparum malaria is not adequately described due to the lack of longitudinal studies in this population. The present study was conducted to partially fill this gap. METHODS: Participants were recruited through Health Care Provider's safety registry in 15 centres across 6 European countries in the period 2013-2016. Adverse events (AE) were collected, with a special focus on cardiovascular safety by including electrocardiogram QT intervals evaluated after correction with either Bazett's (QTcB) or Fridericia's (QTcF) methods, at baseline and after treatment. QTcB and/or QTcF prolongation were defined by a value > 450 ms for males and children and > 470 ms for females. RESULTS: Among 294 participants, 30.3% were women, 13.7% of Caucasian origin, 13.5% were current smoker, 13.6% current alcohol consumer and 42.2% declared at least one illness history. The mean (SD) age and body mass index were 39.8 years old (13.2) and 25.9 kg/m2 (4.7). Among them, 75 reported a total of 129 AE (27 serious), 46 being suspected to be related to APQ (11 serious) and mostly labelled as due to haematological, gastrointestinal, or infection. Women and Non-African participants had significantly (p < 0.05) more AEs. Among AEs, 21 were due to cardiotoxicity (7.1%), mostly QT prolongation, while 6 were due to neurotoxicity (2.0%), mostly dizziness. Using QTcF correction, QT prolongation was observed in 17/143 participants (11.9%), only 2 of them reporting QTcF > 500 ms (milliseconds) but no clinical symptoms. Using QTcB correction increases of > 60 ms were present in 9 participants (6.3%). A trend towards increased prolongation was observed in those over 65 years of age but only a few subjects were in this group. No new safety signal was reported. The overall efficacy rate was 255/257 (99.2%). CONCLUSIONS: APQ appears as an effective and well-tolerated drug for treatment of malaria in patients recruited in European countries. AEs and QT prolongation were in the range of those obtained in larger cohorts from endemic countries. Trial registration This study has been registered in EU Post-Authorization Studies Register as EUPAS6942.

Safety, tolerability, pharmacokinetics, pharmacodynamics, bioavailability and food effect of single doses of soticlestat in healthy subjects.

AIMS: Soticlestat is a first-in-class selective inhibitor of cholesterol 24-hydroxylase, the enzyme that converts brain cholesterol to 24S-hydroxycholesterol (24HC), a positive allosteric modulator of N-methyl-D-aspartate receptors. Soticlestat is under development as treatment for rare developmental and epileptic encephalopathies. METHODS: In this first-in-human study, 48 healthy men and women received single ascending doses of soticlestat oral solution or placebo. Subsequently, nine healthy subjects received soticlestat tablets under fed and fasting conditions to assess the relative oral bioavailability and effects of food. Serial blood and urine samples were collected for pharmacokinetic and pharmacodynamic assessments. RESULTS: Soticlestat appeared to be well tolerated up to a single dose of 1350 mg. Adverse events (AEs) were mild in intensity, and dose-dependent increase in AE prevalence was not apparent. Soticlestat administered via oral solution was rapidly absorbed (median time to maximum plasma concentration [Cmax ] 0.250-0.520 h). Mean Cmax and area under plasma concentration-time curve from zero to infinity increased by 183- and 581-fold, respectively, over a 90-fold dose increase. Mean terminal elimination half-life was 0.820-7.16 hours across doses. Renal excretion was negligible. Administration of soticlestat tablets, and with food, lowered Cmax but did not affect overall exposure. Plasma 24HC concentrations generally decreased with increasing dose. CONCLUSIONS: Soticlestat appeared to be well tolerated after a single oral administration of up to 1350 mg and dose-dependently reduced plasma 24HC concentrations. Systemic exposure increased in a greater than dose-proportional manner over the dose range evaluated but was not affected by formulation or administration with food.

Digital biomarker-based individualized prognosis for people at risk of dementia.

Background: Research investigating treatments and interventions for cognitive decline fail due to difficulties in accurately recognizing behavioral signatures in the presymptomatic stages of the disease. For this validation study, we took our previously constructed digital biomarker-based prognostic models and focused on generalizability and robustness of the models. Method: We validated prognostic models characterizing subjects using digital biomarkers in a longitudinal, multi-site, 40-month prospective study collecting data in memory clinics, general practitioner offices, and home environments. Results: Our models were able to accurately discriminate between healthy subjects and individuals at risk to progress to dementia within 3 years. The model was also able to differentiate between people with or without amyloid neuropathology and classify fast and slow cognitive decliners with a very good diagnostic performance. Conclusion: Digital biomarker prognostic models can be a useful tool to assist large-scale population screening for the early detection of cognitive impairment and patient monitoring over time.

Negative Symptoms of Schizophrenia and Dopaminergic Transmission: Translational Models and Perspectives Opened by iPSC Techniques.

Negative symptoms (NS) represent a heterogeneous dimension of schizophrenia (SCZ), associated with a poor functional outcome. A dysregulated dopamine (DA) system, including a reduced D1 receptor activation in the prefrontal cortex, DA hypoactivity in the caudate and alterations in D3 receptor activity, seems to contribute to the pathogenesis of NS. However, failure to take into account the NS heterogeneity has slowed down progress in research on their neurobiological correlates and discoveries of new effective treatments. A better neurobiological characterization of NS is needed, and this requires objective quantification of their features that can be applied in translational models, such as animal models and human inducible pluripotent stem cells (iPSC). In this review we summarize the evidence for dopaminergic alterations relevant to NS in translational animal models focusing on dysfunctional motivation, a core aspect of NS. Among others, experiments on mutant rodents with an overexpression of DA D2 or D3 receptors and the dopamine deficient mice are discussed. In the second part we summarize the findings from recent studies using iPSC to model the pathogenesis of SCZ. By retaining the genetic background of risk genetic variants, iPSC offer the possibility to study the effect of de novo mutations or inherited polymorphisms from subgroups of patients and their response to drugs, adding an important tool for personalized psychiatry. Given the key role of DA in NS, we focus on findings of iPSC-derived DA neurons. Since implementation of iPSC-derived neurons to study the neurobiology of SCZ is a relatively recent acquisition, the available data are limited. We highlight some methodological aspects of relevance in the interpretation of in vitro testing results, including limitations and strengths, offering a critical viewpoint for the implementation of future pharmacological studies aimed to the discovery and characterization of novel treatments for NS.

Social dysfunction in mood disorders and schizophrenia: Clinical modulators in four independent samples.

INTRODUCTION: Social dysfunction is a common symptom of several neuropsychiatric disorders. However, only in the last few years research began to systematically investigate clinical aspects of this relevant outcome. Interestingly, its distribution and link with other clinical variables is still unclear. This study investigated social dysfunction in 4 different cohorts of patients affected by mood disorders and schizophrenia to evaluate 1) the degree of social dysfunction in these populations; 2) the associations among social dysfunction and socio-demographic and psychopathological features. METHODS: Data from 4 independent studies (CATIE, GSRD ES1, ES2 and ES3, STAR*D, STEP-BD) were investigated. Behavioural and affective indicators of social dysfunction were derived and operationalized from scales or questionnaire items related to the interaction with relatives, friends and significant people in patients affected by schizophrenia (N = 765) and mood disorders (N = 2278 + 1954 + 1829). In particular the social dysfunction indicator was derived from Sheehan Disability Scale (SDS) for GSRD sample, from the Work and Social Adjustment Scale (WSAS) for STAR*D sample, from the Life-Range of Impaired Functioning Tool (LRIFT) for STEP-BD sample, and from the Quality of Life Scale (QOLS) for CATIE sample. The distribution of social dysfunction was described and association with socio-demographic and psychopathological characteristics were analysed. RESULTS: Social dysfunction indicators showed a broad distribution in all samples investigated. Consistently across studies, social dysfunction was associated with higher psychopathological severity (all samples except CATIE) and suicide risk (GSRD ES1 and ES2, STAR*D, and STEP-BD) that explain up to 47% of the variance, but also to lower education level (GSRD ES2, STAR*D, CATIE, and STEP-BD), poorer professional/work status (GSRD ES2 and ES3, STAR*D, CATIE, and STEP-BD), marital status (STAR*D and CATIE), age (younger age in GSRD ES1 and STAR*D, older age in CATIE), higher BMI (GSRD ES2 and ES3, and STEP-BD), and smoking (GSRD ES2 and ES3). CONCLUSION: Our results demonstrated that a significant percentage of patients affected by both mood disorders and schizophrenia shows relevant social dysfunction. Social dysfunction is related, but not completely explained by psychopathological severity. In several patients, it tends to persist also during remission state. Socio-demographic and lifestyle factors were also found to play a role and should therefore be taken into consideration in further studies investigating social dysfunction.

Structural Plasticity Induced by Ketamine in Human Dopaminergic Neurons as Mechanism Relevant for Treatment-Resistant Depression.

The mechanisms underlying the antidepressant effects of ketamine in treatment-resistant depression are only partially understood. Reactivation of neural plasticity in prefrontal cortex has been considered critical in mediating the effects of standard antidepressants, but in treatment-resistant depression patients with severe anhedonia, other components of the affected brain circuits, for example, the dopamine system, could be involved. In a recent article in Molecular Psychiatry, we showed that ketamine induces neural plasticity in human and mouse dopaminergic neurons. Human dopaminergic neurons were differentiated from inducible pluripotent stem cells for over 60 days. Mimicking the pharmacokinetic exposures occurring in treatment-resistant depression subjects, cultures were incubated with either ketamine at 0.1 and 1 µM for 1 h or with its active metabolite (2R,6R)-hydroxynorketamine at 0.1 and 0.5 µM for up to 6 h. Three days after dosing, we observed a concentration-dependent increase in dendritic arborization and soma size. These effects were mediated by the activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor that triggered the pathways of mammalian target of rapamycin and extracellular signal-regulated kinase via the engagement of brain-derived neurotrophic factor signaling, as previously described in rodent prefrontal cortex. Interestingly, we found that neural plasticity induced by ketamine requires functionally intact dopamine D3 receptors. These data are in keeping with our recent observation that plasticity can be induced in human dopaminergic neurons by the D3 receptor-preferential agonist pramipexole, whose effect as augmentation treatment in treatment-resistant depression has been reported. Overall, the evidence of pharmacologic response in human inducible pluripotent stem cell-derived neurons could provide complementary information to those provided by circuit-based imaging when assessing the potential response to a given augmentation treatment.

Relating constructs of attention and working memory to social withdrawal in Alzheimer's disease and schizophrenia: issues regarding paradigm selection.

Central nervous system diseases are not currently diagnosed based on knowledge of biological mechanisms underlying their symptoms. Greater understanding may be offered through an agnostic approach to traditional disease categories, where learning more about shared biological mechanisms across conditions could potentially reclassify sub-groups of patients to allow realisation of more effective treatments. This review represents the output of the collaborative group "PRISM", tasked with considering assay choices for assessment of attention and working memory in a transdiagnostic cohort of Alzheimer's disease and schizophrenia patients exhibiting symptomatic spectra of social withdrawal. A multidimensional analysis of this nature has not been previously attempted. Nominated assays (continuous performance test III, attention network test, digit symbol substitution, N-back, complex span, spatial navigation in a virtual environment) reflected a necessary compromise between the need for broad assessment of the neuropsychological constructs in question with several pragmatic criteria: patient burden, compatibility with neurophysiologic measures and availability of preclinical homologues.

Ketamine increases the expression of GluR1 and GluR2 α-amino-3-hydroxy-5-methy-4-isoxazole propionate receptor subunits in human dopaminergic neurons differentiated from induced pluripotent stem cells.

The mechanisms underlying the prolonged antidepressant effects after a single exposure to ketamine are only partially understood. Converging findings indicate a critical role of structural neuroplasticity, recently also proposed for dopaminergic (DA) neurons known to be involved in a depression core symptom, anhedonia. We recently showed that ketamine induces dendritic outgrowth in human DA neurons differentiated in-vitro from induced pluripotent stem cells of healthy donors, a phenomenon blocked by the α-amino-3-hydroxy-5-methy-4-isoxazole propionate receptor antagonist NBQX. As changes in the expression of AMPA receptor subunits GluR1 and GluR2 were observed in neuroplasticity of rodent DA neurons, we aimed to explore this phenomenon in human DA neurons. Using specific antibodies against GluR1 and GluR2 α-amino-3-hydroxy-5-methy-4-isoxazole propionate receptor subunits, we showed that GluR1 levels were significantly higher in soma than in dendrites, whereas for GluR2, levels were significantly higher in dendrites than in soma. One hour exposure to 1 µM ketamine increased the signal of both subunits in dendrites, but only of GluR2 in soma, at 24, 48, and 72 h. Nonlinear polynomial fitting of dendritic expression indicated that the two curves were significantly different, with stronger and more sustained effects on GluR2 expression. Overall, these data support a role for GluR1 and GluR2 dendritic upregulation in driving structural plasticity in human DA neurons depending on ketamine transient exposure, indicating translationally relevant downstream mechanism possibly involved in antidepressant effects.