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[EN] Objective Recently, we reported on a new MDD-like mouse model based on a regionally selective knockdown of astroglial glutamate transporters, GLAST/GLT-1, in infralimbic cortex (IL) which evokes widespread changes in mouse brain associated with the typical alterations found in MDD patients. To further characterize this new MDD-like mouse model, here we examine some transcriptional elements of glutamatergic/GABAergic neurotransmission and neuroplasticity in forebrain regions in the GLT-1 knockdown mice. Furthermore, we assess the acute ketamine effects on these transcriptional processes. Material and methods We used a small interfering RNA (siRNA) pool targeting GLT-1 mRNA to disrupt the GLT-1 transcription in mouse IL. Histological assays were performed to examine postsynaptic density protein-95 (PSD95), neuritin (NRN), glutamine acid descarboxilase-65 (GAD65), and GLT-1 mRNA expression in IL and hippocampus. Results Knockdown of GLT-1 in mouse IL leads to decreased expression of PSD95 and NRN neuroplasticity mRNAs in IL and hippocampus, which was reversed by an acute dose of ketamine antidepressant. Likewise, a single dose of ketamine also increased the mRNA levels of GAD65 and GLT-1 in IL of GLT-1 knockdown mice, reaching the basal values of control mice. Conclusions The glutamatergic neuronal hyperactivity and deficits in the GABA system resulting from siRNA-induced astroglial glutamate transporter knockdown in IL can compromise the integrity/plasticity of neurocircuits affected in MDD. Suitable depressive-like animal models to address the neurobiological changes in MDD are an unmet need and the development of the GLAST/GLT-1 knockdown mouse model may represent a better option to understand the rapid-acting antidepressant effects of ketamine., [ES] Objetivo Recientemente, informamos sobre un nuevo modelo de ratón de depresión basado en una reducción parcial de la transcripción de los transportadores de glutamato, GLAST/GLT-1, en los astrocitos de la corteza infralímbica (IL), que conduce a cambios generalizados de la función cerebral del ratón, que refleja alteraciones típicas encontradas en pacientes con depresión. Para caracterizar más detalladamente este nuevo modelo de ratón de depresión, aquí examinamos algunos elementos transcripcionales relacionados con la neurotransmisión glutamatérgica/GABAérgica y la neuroplasticidad en regiones corticales y subcorticales de los ratones con niveles reducidos de GLT-1. Además, evaluamos los efectos agudos de la ketamina, antidepresivo de acción rápida, en estos procesos transcripcionales. Material y métodos Utilizamos ARN de interferencia (siRNA) dirigido al mRNA de GLT-1 para interrumpir su transcripción en la IL de ratón. Se realizaron ensayos histológicos para examinar la expresión de los mRNA de las siguientes proteínas: proteína de densidad postsináptica-95 (PSD95), neuritina (NRN), descarboxilasa de ácido glutámico-65 (GAD65) y GLT-1 en la IL e hipocampo. Resultados La reducción de la expresión de GLT-1 en IL de ratón conduce a una disminución de la expresión de los mRNA de neuroplasticidad PSD95 y NRN en la IL y el hipocampo, efecto que se revirtió con una única administración del antidepresivo ketamina. Asimismo, una sola dosis de ketamina también aumentó los niveles de los mRNA de GAD65 y GLT-1 en la IL de ratones silenciados para GLT-1, que alcanzaron los valores basales de los ratones control. Conclusiones La hiperactividad neuronal glutamatérgica y los déficits en el sistema GABAérgico resultantes de la reducción de los niveles del transportador de glutamato astroglial inducida por siRNA en IL pueden comprometer la integridad/plasticidad de aquellos neurocircuitos afectados en la depresión. Sin embargo, no disponemos de modelos animales de depresión adecuados para abordar los cambios neurobiológicos que se suceden en esta enfermedad y su tratamiento. El desarrollo del modelo de ratón con reducción parcial de GLAST/GLT-1 puede representar una mejor opción para comprender los efectos antidepresivos de acción rápida de la ketamina., This study was supported by grants SAF2016-75797-R, PID2019-105136RB-100, Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE; and CB/07/09/0034 Center for Networked Biomedical Research on Mental Health (CIBERSAM).

The infralimbic (IL) cortex is the rodent equivalent of human ventral anterior cingulate cortex (vACC), which plays a key role in the pathophysiology and treatment of major depressive disorder (MDD). The modulation of glutamatergic neurotransmission in IL [but not in the adjacent prelimbic (PrL) cortex] evokes antidepressant-like or depressive-like behaviors, associated with changes in serotonin (5-HT) function, highlighting the relevance of glutamate/serotonin interactions in IL for emotional control. 5-HT modulates neuronal activity in PrL and cingulate (Cg) cortex but its effects in IL are largely unknown. We therefore compared the in vivo effects of 5-HT on pyramidal neuron activity in IL (n = 61) and PrL (n = 50) of anesthetized rats. IL pyramidal neurons were more responsive to physiological dorsal raphe stimulation (0.9 Hz) than PrL neurons (84% vs. 64%, respectively) and were inhibited to a greater extent (64% vs. 36%, respectively). Orthodromic activations (8% in PrL) were absent in IL, whereas biphasic responses were similar (20%) in both areas. Excitations were mediated by 5-HT2A-R activation, whereas inhibitions involved 3 different components: 5-HT1A-R, 5-HT3-R and GABAA-R, respectively. The remarkable inhibitory action of 5-HT in IL suggests that 5-HT-enhancing drugs may exert their antidepressant action by normalizing a glutamatergic hyperactivity in the vACC of MDD patients., Spanish Ministry of Economy and Competitiveness (SAF2015-68346-P MINECO/FEDER, UE to F.A., PI16/00287 to P.C.; European Regional Development Fund “A way to build Europe.”; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM);CERCA Programme from the Generalitat de Catalunya. The authors of this study would like to thank the support of the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2017SGR717). E.L.T. is recipient of a predoctoral contract from Spanish MINECO

The central serotonin

Tyrosine hydroxylase deficiency (THD) is a rare genetic disorder leading to dopaminergic depletion and early-onset parkinsonism. Affected children present with either a severe form that does not respond to L-Dopa treatment (THD-B), or a milder L-Dopa responsive form (THD-A). We generated induced pluripotent stem cells (iPSCs) from THD patients that were differentiated into dopaminergic neurons (DAn) and compared with control-DAn from healthy individuals and gene-corrected isogenic controls. Consistent with patients, THD iPSC-DAn displayed lower levels of DA metabolites and reduced TH expression, when compared to controls. Moreover, THD iPSC-DAn showed abnormal morphology, including reduced total neurite length and either an abnormal TH proximodistal gradient (THDA), or neurite arborization defects (THDB). Treatment of THD-iPSC-DAn with L-Dopa rescued the neuronal defects and disease phenotype only in THDA-DAn. Interestingly, L-Dopa treatment at the stage of neuronal precursors could prevent the alterations in THDB-iPSC-DAn, thus suggesting the existence of a critical developmental window in THD. Our iPSC-based model recapitulates THD disease phenotypes and response to treatment, representing a promising tool for investigating pathogenic mechanisms, drug screening, and personalized management.

Anxiety and depression affect 35–50% of patients with Parkinson’s disease (PD), often precede the onset of motor symptoms, and have a negative impact on their quality of life. Dysfunction of the serotonergic (5-HT) system, which regulates mood and emotional pathways, occurs during the premotor phase of PD and contributes to a variety of non-motor symptoms. Furthermore, α-synuclein (α-Syn) aggregates were identified in raphe nuclei in the early stages of the disease. However, there are very few animal models of PD-related neuropsychiatric disorders. Here, we develop a new mouse model of α-synucleinopathy in the 5-HT system that mimics prominent histopathological and neuropsychiatric features of human PD. We showed that adeno-associated virus (AAV5)-induced overexpression of wild-type human α-Syn (h-α-Syn) in raphe 5-HT neurons triggers progressive accumulation, phosphorylation, and aggregation of h-α-Syn protein in the 5-HT system. Specifically, AAV5-injected mice displayed axonal impairment in the output brain regions of raphe neurons, and deficits in brain-derived neurotrophic factor (BDNF) expression and 5-HT neurotransmission, resulting in a depressive-like phenotype. Intracerebroventricular treatment with an indatraline-conjugated antisense oligonucleotide (IND-ASO) for four weeks induced an effective and safe reduction of h-α-Syn synthesis in 5-HT neurons and its accumulation in the forebrain, alleviating early deficits of 5-HT function and improving the behavioural phenotype. Altogether, our findings show that α-synucleinopathy in 5-HT neurons negatively affects brain circuits that control mood and emotions, resembling the expression of neuropsychiatric symptoms occurring at the onset of PD. Early preservation of 5-HT function by reducing α-Syn synthesis/accumulation may alleviate PD-related depressive symptoms., We thank to the Coordenação de Aperfeiçoamento de Nivel Superior (CAPES-PDSE: 19/2016 88881.135527/2016-01), Brazil, for their financial support via a scholarship awarded to C.C.-S. We also thank JAE-Intro Program, CSIC (JAEINT_20_02116), Spain, for their financial support via a scholarship awarded to M.T.-L. This study was supported by grants SAF2016-75797-R, PID2019-105136RB-100, Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE; and CB/07/09/0034 Center for Networked Biomedical Research on Mental Health (CIBERSAM).

Schizophrenia is a severe mental disorder featuring psychotic, depressive, and cognitive alterations. Current antipsychotic drugs preferentially target dopamine D2-R and/or serotonergic 5-HT2A/1A-R. They partly alleviate psychotic symptoms but fail to treat negative symptoms and cognitive deficits. Here we report on the putative antipsychotic activity of (1-[(3-fluorophenyl)sulfonyl]-4-(piperazin-1-yl)-1H-pyrrolo[3,2-c]quinoline dihydrochloride) (FPPQ), a dual serotonin 5-HT3-R/5-HT6-R antagonist endowed with pro-cognitive properties. FPPQ fully reversed phencyclidine-induced decrease of low-frequency oscillations in the medial prefrontal cortex of anaesthetized rats, a fingerprint of antipsychotic activity. This effect was mimicked by the combined administration of the 5-HT3-R and 5-HT6-R antagonists ondansetron and SB-399a885, respectively, but not by either drug alone. In freely moving rats, FPPQ countered phencyclidine-induced hyperlocomotion and augmentation of gamma and high-frequency oscillations in medial prefrontal cortex, dorsal hippocampus, and nucleus accumbens. Overall, this supports that simultaneous blockade of 5-HT3R and 5-HT6-R-like that induced by FPPQ-can be a new target in antipsychotic drug development., This work was supported by a grant agreement between IDIBAPS and Spherium, the CERCA Programme (Generalitat de Catalunya), Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), and Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2017SGR717).

Major Depressive Disorder (MDD) is a mood disorder characterized by a large number and variety of symptoms, including affective/emotional (persistent sadness, anhedonia, anxiety, agitation, guilt feelings, hopelessness, etc.), somatic (tiredness, loss of energy, sleep disturbances, reduced/increased appetite, weight gain/loss etc.) and cognitive symptoms (slowness of thinking, concentration difficulties, etc.). Overall, this suggests the presence of derangements of nerve transmission in different areas/circuits involved in the control of these disturbed brain functions., Supported by the Spanish Ministry of Economy and Competitiveness, SAF2015–68346-P MINECO/FEDER, co-financed by the European Regional Development Fund “A way to build Europe”. Supported also by the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and by CERCA Programme from the Generalitat de Catalunya. I also would like to thank the support of the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya (2017SGR717).

International audience; Serotonin2B receptor (5-HT2BR) antagonists inhibit cocaine-induced hyperlocomotion independently of changes of accumbal dopamine (DA) release. Given the tight relationship between accumbal DA activity and locomotion, and the inhibitory role of medial prefrontal cortex (mPFC) DA on subcortical DA neurotransmission and DA-dependent behaviors, it has been suggested that the suppressive effect of 5-HT2BR antagonists on cocaine-induced hyperlocomotion may result from an activation of mPFC DA outflow which would subsequently inhibit accumbal DA neurotransmission. Here, we tested this hypothesis by means of the two selective 5-HT2BR antagonists, RS 127445 and LY 266097, using a combination of neurochemical, behavioral and cellular approaches in male rats. The intraperitoneal (i.p.) administration of RS 127445 (0.16 mg/kg) or LY 266097 (0.63 mg/kg) potentiated cocaine (10 mg/kg, i.p.)-induced mPFC DA outflow. The suppressant effect of RS 127445 on cocaine-induced hyperlocomotion was no longer observed in rats with local 6-OHDA lesions in the mPFC. Also, RS 127445 blocked cocaine-induced changes of accumbal glycogen synthase kinase (GSK) 3β phosphorylation, a postsynaptic cellular marker of DA neurotransmission. Finally, in keeping with the location of 5-HT2BRs on GABAergic interneurons in the dorsal raphe nucleus (DRN), the intra-DRN perfusion of the GABAAR antagonist bicuculline (100 μM) prevented the effect of the systemic or local (1 μM, intra-DRN) administration of RS 127445 on cocaine-induced mPFC DA outflow. Likewise, intra-DRN bicuculline injection (0.1 μg/0.2 μl) prevented the effect of the systemic RS 127445 administration on cocaine-induced hyperlocomotion and GSK3β phosphorylation. These results show that DRN 5-HT2BR blockade suppresses cocaine-induced hyperlocomotion by potentiation of cocaine-induced DA outflow in the mPFC and the subsequent inhibition of accumbal DA neurotransmission.

Huntington's disease (HD) is a neurological disorder characterized by motor disturbances. HD pathology is most prominent in the striatum, the central hub of the basal ganglia. The cerebral cortex is the main striatal afferent, and progressive cortico-striatal disconnection characterizes HD. We mapped striatal network dysfunction in HD mice to ultimately modulate the activity of a specific cortico-striatal circuit to ameliorate motor symptoms and recover synaptic plasticity. Multimodal MRI in vivo indicates cortico-striatal and thalamo-striatal functional network deficits and reduced glutamate/glutamine ratio in the striatum of HD mice. Moreover, optogenetically-induced glutamate release from M2 cortex terminals in the dorsolateral striatum (DLS) was undetectable in HD mice and striatal neurons show blunted electrophysiological responses. Remarkably, repeated M2-DLS optogenetic stimulation normalized motor behavior in HD mice and evoked a sustained increase of synaptic plasticity. Overall, these results reveal that selective stimulation of the M2-DLS pathway can become an effective therapeutic strategy in HD., We are very grateful to Ana Lopez (María de Maeztu Unit of Excellence, Institute of Neurosciences, University of Barcelona, MDM-2017–0729, Ministry of Science, Innovation, and Universities) and Maite Muñoz for their excellent technical support. This work has been funded by the Spanish Ministry of Sciences, Innovation and Universities through projects no. SAF2017-88076-R, RETICS de Terapia Celular, Instituto de Salud Carlos III (RD06/0010/0006), and la Marato´ de TV3. This research is part of NEUROPA. The NEUROPA Project has received funding from the European Union’s Horizon 2020 Research and Innovation Program under Grant Agreement No. 863214.

Progressive neuronal death in monoaminergic nuclei and widespread accumulation of α-synuclein are neuropathological hallmarks of Parkinson's disease (PD). Given that α-synuclein may be an early mediator of the pathological cascade that ultimately leads to neurodegeneration, decreased α-synuclein synthesis will abate neurotoxicity if delivered to the key affected neurons.We used a non-viral gene therapy based on a new indatraline-conjugated antisense oligonucleotide (IND-ASO) to disrupt the α-synuclein mRNA transcription selectively in monoamine neurons of a PD-like mouse model and elderly nonhuman primates. Molecular, cell biology, histological, neurochemical and behavioral assays were performed.Intracerebroventricular and intranasal IND-ASO administration for four weeks in a mouse model with AAV-mediated wild-type human α-synuclein overexpression in dopamine neurons prevented the synthesis and accumulation of α-synuclein in the connected brain regions, improving dopamine neurotransmission. Likewise, the four-week IND-ASO treatment led to decreased levels of endogenous α-synuclein protein in the midbrain monoamine nuclei of nonhuman primates, which are affected early in PD.The inhibition of α-synuclein production in dopamine neurons and its accumulation in cortical/striatal projection areas may alleviate the early deficits of dopamine function, showing the high translational value of antisense oligonucleotides as a disease modifying therapy for PD and related synucleinopathies.Grants SAF2016-75797-R, RTC-2014-2812-1 and RTC-2015-3309-1, Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE; Grant ID 9238, Michael J. Fox Foundation; and Centres for Networked Biomedical Research on Mental Health (CIBERSAM), and on Neurodegenerative Diseases (CIBERNED).

Remarkable advances in understanding the role of RNA in health and disease have expanded considerably in the last decade. RNA is becoming an increasingly important target for therapeutic intervention; therefore, it is critical to develop strategies for therapeutic modulation of RNA function. Oligonucleotides, including antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA mimic (miRNA), and anti-microRNA (antagomir) are perhaps the most direct therapeutic strategies for addressing RNA. Among other mechanisms, most oligonucleotide designs involve the formation of a hybrid with RNA that promotes its degradation by activation of endogenous enzymes such as RNase-H (e.g., ASO) or the RISC complex (e.g. RNA interference - RNAi for siRNA and miRNA). However, the use of oligonucleotides for the treatment of brain disorders is seriously compromised by two main limitations: i) how to deliver oligonucleotides to the brain compartment, avoiding the action of peripheral RNAses? and once there, ii) how to target specific neuronal populations? We review the main molecular pathways in major depressive disorder (MDD) and Parkinson's disease (PD), and discuss the challenges associated with the development of novel oligonucleotide therapeutics. We pay special attention to the use of conjugated ligand-oligonucleotide approach in which the oligonucleotide sequence is covalently bound to monoamine transporter inhibitors (e.g. sertraline, reboxetine, indatraline). This strategy allows their selective accumulation in the monoamine neurons of mice and monkeys after their intranasal or intracerebroventricular administration, evoking preclinical changes predictive of a clinical therapeutic action after knocking-down disease-related genes. In addition, recent advances in oligonucleotide therapeutic clinical trials are also reviewed., This study was supported by grants SAF2016-75797-R and PID2019-105136RB-I00, Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE (to A.B.); and CB/07/09/0034 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM). We thank M. Calvo and E. Coll for outstanding technical support in the confocal microscopy unit (CCiT-UB). We also thank M. Jaramillo for helpful secretarial assistance. Fig. 1, Fig. 3 were generated using online application Motifolio Illustration Toolkits.com and Created with BioRender.com, respectively.

Non-competitive N-methyl-D-aspartate receptor antagonists mimic schizophrenia symptoms and produce immediate and persistent antidepressant effects. We investigated the effects of ketamine and phencyclidine (PCP) on thalamo-cortical network activity in awake, freely-moving male Wistar rats to gain new insight into the neuronal populations and brain circuits involved in the effects of NMDA-R antagonists. Single unit and local field potential (LFP) recordings were conducted in mediodorsal/centromedial thalamus and in medial prefrontal cortex (mPFC) using microelectrode arrays. Ketamine and PCP moderately increased the discharge rates of principal neurons in both areas while not attenuating the discharge of mPFC GABAergic interneurons. They also strongly affected LFP activity, reducing beta power and increasing that of gamma and high-frequency oscillation bands. These effects were short-lasting following the rapid pharmacokinetic profile of the drugs, and consequently were not present at 24 h after ketamine administration. The temporal profile of both drugs was remarkably different, with ketamine effects peaking earlier than PCP effects. Although this study is compatible with the glutamate hypothesis for fast-acting antidepressant action, it does not support a local disinhibition mechanism as the source for the increased pyramidal neuron activity in mPFC. The short-lasting increase in thalamo-cortical activity is likely associated with the rapid psychotomimetic action of both agents but could also be part of a cascade of events ultimately leading to the persistent antidepressant effects of ketamine. Changes in spectral contents of high-frequency bands by the drugs show potential as translational biomarkers for target engagement of NMDA-R modulators., The work leading to these results has received funding from Lundbeck A/S, the Innovation Fund Denmark and SAF2015-68346-P (Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF)) and PI12/00156 and PI16/00287 Instituto de Salud Carlos III, co-financed by European Regional Development Fund (ERDF)). Support from the Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and Generalitat de Catalunya Grup de Recerca Consolidat, 2017SGR717 is also acknowledged. Ulrike Richter is funded by Sweden's Innovation Agency VINNOVA.

9 páginas, 5 figuras, 1 tabla, Lafora disease (LD) is a fatal rare neurodegenerative disorder characterized by epilepsy, neurodegeneration and insoluble polyglucosan accumulation in brain and other peripheral tissues. Although in the last two decades we have increased our knowledge on the molecular basis underlying the pathophysiology of LD, only a small part of the research in LD has paid attention to the mechanisms triggering one of the most lethal features of the disease: epilepsy. Recent studies in our laboratory suggested that a dysfunction in the activity of the mouse astrocytic glutamate transporter 1 (GLT-1) could contribute to epilepsy in LD. In this work, we present new in vivo evidence of a GLT-1 dysfunction, contributing to increased levels of extracellular glutamate in the hippocampus of a mouse model of Lafora disease (Epm2b-/-, lacking the E3-ubiquitin ligase malin). According to our results, Epm2b-/- mice showed an increased neuronal activity, as assessed by c-fos expression, in the hippocampus, an area directly correlated to epileptogenesis. This brain area presented lesser ability to remove synaptic glutamate after local GLT-1 blockade with dihydrokainate (DHK), in comparison to Epm2b+/+ animals, suggesting that these animals have a compromised glutamate clearance when a challenging condition was presented. These results correlate with a hippocampal upregulation of the minor isoform of the Glt-1 gene, named Glt-1b, which has been associated with compensatory mechanisms activated in response to neuronal stress. In conclusion, the hippocampus of Epm2b-/- mice presents an in vivo impairment in glutamate uptake which could contribute to epileptogenesis., This work was supported by grants from the Spanish Ministry of Economy and Competitiveness SAF2014-54604-C3-1-R, SAF2017-83151-R (to P.S.) and SAF2015-68346-P (to F.A.), co-funded by the European Regional Development Fund “A way to build Europe” (to F.A.), a grant from Fundación Ramón Areces (CIVP18A3935) and a grant from the National Institute of Health (NIH-NINDS) P01NS097197, which established the Lafora Epilepsy Cure Initiative (LECI), to P.S. The Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and de Enfermedades Raras (CIBERER) are also acknowledged for financial support. We also thank Letizia Campa and Verónica Paz for their outstanding technical assistance. C.M.-B. holds a FPU fellowship from the Spanish Ministry of Education, Culture and Sports.

Alterations of energy metabolism and of astrocyte number/function in ventral anterior cingulate cortex (vACC) have been reported in major depressive disorder (MDD) patients and may contribute to MDD pathophysiology. We recently developed a mouse model of MDD mimicking these alterations. We knocked down the astroglial glutamate transporters GLAST and GLT-1 in infralimbic cortex (IL, rodent equivalent of vACC) using small interfering RNA (siRNA). GLAST and GLT-1 siRNA microinfusion in IL evoked a depressive-like phenotype, associated with a reduced serotonergic function and reduced forebrain BDNF expression. Neither effect occurred after siRNA application in the adjacent prelimbic cortex (PrL), thus emphasizing the critical role of vACC/IL in MDD pathogenesis. Here we examined the cellular/network basis of the changes induced in IL using intracellular recordings of layer V pyramidal neurons from mice microinjected with siRNA 24 h before. We analyzed (i) the electrophysiological characteristics of neurons; (ii) the synaptic transmission properties, by monitoring miniature, spontaneous and evoked EPSCs, and (iii) the gliotransmission, by monitoring slow inward currents (SICs), mediated by astrocytic glutamate release and activation of extra-synaptic NMDA receptors. GLT-1 and GLAST knockdown led to a more depolarized membrane potential and increased action potential firing rate of layer V pyramidal neurons, and enhanced excitatory synaptic transmission, as shown by the enhanced amplitude/frequency of spontaneous EPSCs. Gliotransmission was also increased, as indicated by the enhanced SIC amplitude/frequency. Hence, the depressive-like phenotype is associated with IL hyperactivity, likely leading to an excessive top-down inhibitory control of serotonergic activity through IL-midbrain descending pathways., This work was supported by the Spanish Ministry of Economy and Competitiveness (grant numbers SAF2015-68346 to F.A., SAF2016-75797-R to A.B.), co-financed by European Regional Development Fund (ERDF) and NIH-NINDS (R01NS097312-01) and Human Frontier Science Program (Research Grant RGP0036/2014) to AA. The Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and CERCA Programme/Generalitat de Catalunya are also acknowledged. N.F. is a recipient of a fellowship from Spanish Ministry of Education, Culture and Sport.

The central serotonin2B receptor (5-HT2BR) is a well-established modulator of dopamine (DA) neuron activity in the rodent brain. Recent studies in rats have shown that the effect of 5-HT2BR antagonists on accumbal and medial prefrontal cortex (mPFC) DA outflow results from a primary action in the dorsal raphe nucleus (DRN), where they activate 5-HT neurons innervating the mPFC. Although the mechanisms underlying this interaction remain largely unknown, data in the literature suggest the involvement of DRN GABAergic interneurons in the control of 5-HT activity. The present study examined this hypothesis using in vivo (intracerebral microdialysis) and in vitro (immunohistochemistry coupled to reverse transcription-polymerase chain reaction) experimental approaches in rats. Intraperitoneal (0.16 mg/kg) or intra-DRN (1 μM) administration of the selective 5-HT2BR antagonist RS 127445 increased 5-HT outflow in both the DRN and the mPFC, these effects being prevented by the intra-DRN perfusion of the GABAA antagonist bicuculline (100 μM), as well as by the subcutaneous (0.16 mg/kg) or the intra-DRN (0.1 μM) administration of the selective 5-HT1AR antagonist WAY 100635. The increase in DRN 5-HT outflow induced by the intra-DRN administration of the selective 5-HT reuptake inhibitor citalopram (0.1 μM) was potentiated by the intra-DRN administration (0.5 μM) of RS 127445 only in the absence of bicuculline perfusion. Finally, in vitro experiments revealed the presence of the 5-HT2BR mRNA on DRN GABAergic interneurons. Altogether, these results show that, in the rat DRN, 5-HT2BRs are located on GABAergic interneurons, and exert a tonic inhibitory control on 5-HT neurons innervating the mPFC., This study was supported by the Institut National de la Santé et de la Recherche Médicale (INSERM) and Bordeaux University and by grant SAF2015-68346-P from the Spanish Ministry of Economy and Competitiveness.

Elevation of energy metabolism and disturbance of astrocyte number/function in the ventral anterior cingulate cortex (vACC) contributes to the pathophysiology of major depressive disorder (MDD). Functional hyperactivity of vACC may result from reduced astrocytic glutamate uptake and increased neuronal excitation. Here we tested this hypothesis by knocking‐down astrocytic glutamate transporter GLAST/GLT‐1 expression in mouse infralimbic (IL, rodent equivalent of vACC) or prelimbic (PrL) cortices using RNAi strategies. Unilateral siRNA (small interfering RNA) microinfusion targeting GLAST or GLT‐1 in mouse IL induced a moderate (20–30%) and long‐lasting (7 days) decrease in their expression. Intra‐IL GLAST‐/GLT‐1 siRNA microinfusion reduced the number of glial fibrillary acidic protein (GFAP)‐positive and glutamine synthetase (GS)‐positive astrocytes and evoked a depressive‐like phenotype reversed by citalopram and ketamine. Intra‐IL GLAST or GLT‐1 knockdown markedly reduced serotonin (5‐HT) release in the dorsal raphe nucleus (DR) and induced an overall reduction of brain‐derived neurotrophic factor (BDNF) expression in ipsilateral and contralateral hemispheres. Egr‐1 (early growth response protein‐1) labeling suggests that both siRNAs enhance the GABAergic tone onto DR 5‐HT neurons, leading to an overall decrease of 5‐HT function, likely related to the widespread reduction on BDNF expression. Conversely, similar reductions of GLAST and GLT‐1 expression in PrL did not induce a depressive‐like phenotype. These results suggest that a focal glial change in IL translates into global change of brain activity by virtue of the descending projections from IL to DR and the subsequent attenuation of serotonergic function in forebrain, an effect perhaps related to the varied symptomatology of MDD., This study was supported by the Spanish Ministry of Economy and Competitiveness, SAF2015‐68346‐P (F.A.) and SAF2016‐75797‐R (A.B.); Retos‐Colaboración Subprogram RTC‐2015‐3309‐1 (A.B.) cofinanced by the European Regional Development Fund “A way to build Europe”. Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and CERCA Programme/Generalitat de Catalunya is also acknowledged. N.F. is a recipient of a fellowship from Spanish Ministry of Education, Culture, and Sport.

Parental behavioural traits can be transmitted by non-genetic mechanisms to the offspring. Although trait transmission via sperm has been extensively researched, epidemiological studies indicate the exclusive/prominent maternal transmission of many non-genetic traits. Since maternal conditions impact the offspring during gametogenesis and through fetal/early-postnatal life, the resultant phenotype is likely the aggregate of consecutive germline and somatic effects; a concept that has not been previously studied. Here, we dissected a complex maternally transmitted phenotype, reminiscent of comorbid generalized anxiety/depression, to elementary behaviours/domains and their transmission mechanisms in mice. We show that four anxiety/stress-reactive traits are transmitted via independent iterative-somatic and gametic epigenetic mechanisms across multiple generations. Somatic/gametic transmission alters DNA methylation at enhancers within synaptic genes whose functions can be linked to the behavioural traits. Traits have generation-dependent penetrance and sex specificity resulting in pleiotropy. A transmission-pathway-based concept can refine current inheritance models of psychiatric diseases and facilitate the development of better animal models and new therapeutic approaches., We are grateful for grant support R01-MH103102 and R21-MH103715 from the NIH to M.T., PO1-HD067244 and R37-HL87062 to S.S.G., 2R01-NS056049 to G.D.P., R01-HL069929, R01-AI080455 and R01-AI101406 to M.R.M. Also supported by the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and grants SAF2015-68346-P to F.A. and PI13/01390 to A.B., co-financed by the European Regional Development Fund. E.M. was supported in part by NIH T32-GM073546.

Major depressive disorder (MDD) is a leading cause of disability worldwide, with a poorly known pathophysiology and sub-optimal treatment, based on serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors. We review existing theories on MDD, paying special attention to the role played by the ventral anterior cingulate cortex (vACC) or its rodent equivalent, infralimbic cortex (IL), which tightly control the activity of brainstem monoamine neurons (including raphe 5-HT neurons) via descending afferents. Further, astrocytes regulate excitatory synapse activity via glutamate reuptake through astrocytic transporters EAAT1 and EAAT2 (GLAST and GLT-1 in rodents), and alterations of astrocyte number/function have been reported in MDD patients and suicide victims. We recently assessed the impact of reducing GLAST/GLT-1 function in IL on emotional behavior and serotonergic function in rodents. The acute pharmacological blockade of GLT-1 with dihydrokainate (DHK) in rat IL evoked an antidepressant-like effect mediated by local AMPA-R activation and a subsequent enhancement of serotonergic function. No effects were produced by DHK microinfusion in prelimbic cortex (PrL). In the second model, a moderate small interfering RNAs (siRNA)-induced reduction of GLAST and GLT-1 expression in mouse IL markedly increased local glutamatergic neurotransmission and evoked a depressive-like phenotype (reversed by citalopram and ketamine), and reduced serotonergic function and BDNF expression in cortical/hippocampal areas. As for DHK, siRNA microinfusion in PrL did not evoke behavioral/neurochemical effects. Overall, both studies support a critical role of the astrocyte-neuron communication in the control of excitatory neurotransmission in IL, and subsequently, on emotional behavior, via the downstream associated changes on serotonergic function., This study was supported by the Spanish Ministry of Economy and Competitiveness, SAF2015-68346-P MINECO/FEDER, UE (F.A.) and SAF2016-75797-R AEI/FEDER, UE (A.B.) co-financed by the European Regional Development Fund “A way to build Europe”. Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and CERCA Programme/Generalitat de Catalunya is also acknowledged. The authors would also like to thank the support of the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2017SGR717). N.F. was a recipient of a fellowship from Spanish Ministry of Education, Culture, and Sport. J.G-C was a recipient of a fellowship from the Spanish Ministry of Economy and Competitiveness (BES-2013-063241). M.T-G was a recipient of a fellowship from Generalitat de Catalunya (2016FI_B 00285) co-financed by the European Social Fund.

5-MeO-DMT is a natural hallucinogen acting as serotonin 5-HT/5-HT receptor agonist. Its ability to evoke hallucinations could be used to study the neurobiology of psychotic symptoms and to identify new treatment targets. Moreover, recent studies revealed the therapeutic potential of serotonin hallucinogens in treating mood and anxiety disorders. Our previous results in anesthetized animals show that 5-MeO-DMT alters cortical activity via 5-HT and 5-HT receptors. Here, we examined 5-MeO-DMT effects on oscillatory activity in prefrontal (PFC) and visual (V1) cortices, and in mediodorsal thalamus (MD) of freely-moving wild-type (WT) and 5-HT-R knockout (KO2A) mice. We performed local field potential multi-recordings evaluating the power at different frequency bands and coherence between areas. We also examined the prevention of 5-MeO-DMT effects by the 5-HT-R antagonist WAY-100635. 5-MeO-DMT affected oscillatory activity more in cortical than in thalamic areas. More marked effects were observed in delta power in V1 of KO2A mice. 5-MeO-DMT increased beta band coherence between all examined areas. In KO2A mice, WAY100635 prevented most of 5-MeO-DMT effects on oscillatory activity. The present results indicate that hallucinatory activity of 5-MeO-DMT is likely mediated by simultaneous alteration of prefrontal and visual activities. The prevention of these effects by WAY-100635 in KO2A mice supports the potential usefulness of 5-HT receptor antagonists to treat visual hallucinations. 5-MeO-DMT effects on PFC theta activity and cortico-thalamic coherence may be related to its antidepressant activity. This article is part of the Special Issue entitled ‘Psychedelics: New Doors, Altered Perceptions’., This work was supported by grants from Instituto de Salud Carlos III (PI09/01245, PI12/00156 and PI16/00287 (PN de I + D + I 2008–2011, ISCIII-Subdirección General de Evaluación y Fomento de la Investigación, Spanish Ministry of Economy and Competitiveness cofinanced by the European Regional Development Fund. “Una manera de hacer Europa”), and by grant SAF2015-68346-P (MINECO, FEDER EU) Centro de Investigación Biomédica en Red de Salud Mental, (CIBERSAM P82, 11INT3. Support from the Generalitat de Catalunya (2014 SGR798) is also acknowledged. MR was supported by an IDIBAPS fellowship.

The central serotonin

Current pharmacological treatments for major depressive disorder (MDD) are severely compromised by both slow action and limited efficacy. RNAi strategies have been used to evoke antidepressant-like effects faster than classical drugs. Using small interfering RNA (siRNA), we herein show that TASK3 potassium channel knockdown in monoamine neurons induces antidepressant-like responses in mice. TASK3-siRNAs were conjugated to cell-specific ligands, sertraline (Ser) or reboxetine (Reb), to promote their selective accumulation in serotonin (5-HT) and norepinephrine (NE) neurons, respectively, after intranasal delivery. Following neuronal internalization of conjugated TASK3-siRNAs, reduced TASK3 mRNA and protein levels were found in the brainstem 5-HT and NE cell groups. Moreover, Ser-TASK3-siRNA induced robust antidepressant-like behaviors, enhanced the hippocampal plasticity, and potentiated the fluoxetine-induced increase on extracellular 5-HT. Similar responses, yet of lower magnitude, were detected for Reb-TASK3-siRNA. These findings provide substantial support for TASK3 as a potential target, and RNAi-based strategies as a novel therapeutic approach to treat MDD., This work was supported by the following grants: SAF2015-68346-P (F.A.); SAF2013-48586-R (J.M.); SAF2016-75797-R (A.B.); Retos-Colaboración Subprograms RTC-2014-2812-1 and RTC-2015-3309-1 (A.B.); Ministry of Economy and Competitiveness (MINECO)—European Regional Development Fund (ERDF), UE; PI13/01390, Instituto de Salud Carlos III co-financed by ERDF (A.B.); IT616-13 Basque Government—ERDF (J.M.); 20003 NARSAD Independent Investigator (A.B.); and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM). CERCA Programme/Generalitat de Catalunya is also acknowledged. M.N.F. and A.F-C. are recipients of a fellowship from the Spanish Ministry of Education, Culture and Sport.

In the second part we focus on two treatment strategies that may overcome the main limitations of current antidepressant drugs. First, we review the experimental and clinical evidence supporting the use of glutamatergic drugs as fast-acting antidepressants. Secondly, we review the involvement of microRNAs (miRNAs) in the pathophysiology of major depressive disorder (MDD) and the use of small RNAs (e.g.., small interfering RNAs or siRNAs) to knockdown genes in monoaminergic and non-monoaminergic neurons and induce antidepressant-like responses in experimental animals. The development of glutamatergic agents is a promising venue for antidepressant drug development, given the antidepressant properties of the non-competitive NMDA receptor antagonist ketamine. Its unique properties appear to result from the activation of AMPA receptors by a metabolite [(2 S,6 S;2 R,6 R)-hydroxynorketamine (HNK)] and mTOR signaling. These effects increase synaptogenesis in prefrontal cortical pyramidal neurons and enhance serotonergic neurotransmission via descending inputs to the raphe nuclei. This view is supported by the cancellation of ketamine's antidepressant-like effects by inhibition of serotonin synthesis. We also review existing evidence supporting the involvement of miRNAs in MDD and the preclinical use of RNA interference (RNAi) strategies to target genes involved in antidepressant response. Many miRNAs have been associated to MDD, some of which e.g., miR-135 targets genes involved in antidepressant actions. Likewise, SSRI-conjugated siRNA evokes faster and/or more effective antidepressant-like responses. Intranasal application of sertraline-conjugated siRNAs directed to 5-HT1A receptors and SERT evoked much faster changes of pre- and postsynaptic antidepressant markers than those produced by fluoxetine., Support from the following grants is acknowledged: SAF2015-68346-P, SAF2016-75797-R and Retos-Colaboración Subprogram RTC-2015–3309-1, MINECO co-financed by European Regional Development Fund - ERDF), UE (Ministry of Economy and Competitiveness and European Regional Development Fund), PI12/00156, PI16/00287 and PI13/01390 (Instituto de Salud Carlos III, co-financed by ERDF, "A way to build Europe"), and Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM. Support from the Generalitat de Catalunya (2014SGR798 and 2017SGR717) is also acknowledged.

Major depressive disorder (MDD) is a severe psychiatric syndrome with high prevalence and socioeconomic impact. Current antidepressant treatments are based on the blockade of serotonin (5-hydroxytryptamine, 5-HT) and/or noradrenaline transporters. These drugs show slow onset of clinical action and limited efficacy, partly due to the activation of physiological negative feed-back mechanisms operating through autoreceptors (5-HT1A, 5-HT1B, α2-adrenoceptors) and postsynaptic receptors (e.g., 5-HT3). As a result, clinically-relevant doses of reuptake inhibitors increase extracellular (active) 5-HT concentrations in the midbrain raphe nuclei but not in forebrain, as indicated by rodent microdialysis studies and by PET-scan studies in primate/human brain. The prevention of these self-inhibitory mechanisms by antagonists of the above receptors augments preclinical and clinical antidepressant effects. Hence, the mixed ß-adrenoceptor/5-HT1A antagonist pindolol accelerated, and in some cases enhanced, the clinical action of selective serotonin reuptake inhibitors (SSRI). This strategy has been incorporated into two new multi-target antidepressant drugs, vilazodone and vortioxetine, which combine 5-HT reuptake inhibition and partial agonism at 5-HT1A receptors. Vortioxetine shows also high affinity for other 5-HT receptors, including excitatory 5-HT3 receptors located in cortical and hippocampal GABA interneurons. 5-HT3 receptor blockade by vortioxetine enhances pyramidal neuron activity in prefrontal cortex as well as cortical and hippocampal 5-HT release. It is still too soon to know whether these new antidepressants will represent a real advance over existing drugs in the real world. However, their development opened the way to future antidepressant drugs based on the prevention of local and distal self-inhibitory mechanisms attenuating monoamine activity., Support from the following grants is acknowledged: grants SAF2015-68346-P, SAF2016-75797-R and Retos-Colaboración Subprogram RTC-2014-2812-1, Ministry of Economy, Industry and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE; grants PI12/00156, PI13/01390 and PI16/00287, Instituto de Salud Carlos III, co-financed by European Regional Development Fund (ERDF), UE, “A way to build Europe”; the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM; Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (Grup de Recerca Consolidat 2014SGR798).

A partial account of the present study was presented at the 29th Congress of the European College of Neuropsychopharmacology, Vienna 2016 and at the Society for Neuroscience 2017 Annual Meeting., [Background] Sub-anesthetic doses of the non-competitive N-methyl-d-aspartate receptor (NMDA-R) antagonist ketamine evoke transient psychotomimetic effects, followed by persistent antidepressant effects in treatment-resistant depressed patients and rodents through still poorly understood mechanisms. Since phencyclidine (PCP) disinhibits thalamo-cortical networks by blocking NMDA-Rs on GABAergic neurons of the reticular thalamic nucleus (RtN), we examined ketamine's actions in the same areas., [Methods] Single units and local field potentials were recorded in chloral hydrate anesthetized male Wistar rats. The effects of cumulative ketamine doses (0.25–5 mg/kg, i.v.) on neuronal discharge and oscillatory activity were examined in RtN, mediodorsal and centromedial (MD/CM) thalamic nuclei, and layer VI of the medial prefrontal cortex (mPFC)., [Results] Ketamine (1, 2 and 5 mg/kg, i.v.) significantly decreased the discharge of MD/CM, RtN and layer VI mPFC pyramidal neurons. Simultaneously, ketamine decreased the power of low frequency oscillations in all areas examined and increased gamma oscillations in mPFC and MD/CM. Lower ketamine doses (0.25 and 0.5 mg/kg, i.v.) were ineffective., [Conclusions] As observed for PCP, ketamine markedly inhibited the activity of RtN neurons. However, unlike PCP, this effect did not translate into a disinhibition of MD/CM and mPFC excitatory neurons, possibly due to a more potent and simultaneous blockade of NMDA-Rs by ketamine in MD/CM and mPFC neurons. Hence, the present in vivo results show that ketamine evokes an early transient inhibition of neuronal discharge in thalamo-cortical networks, following its rapid pharmacokinetics, which is likely associated to its psychotomimetic effects. The prolonged increase in gamma oscillations may underlie its antidepressant action., The work leading to these results has received funding from Lundbeck A/S, the Innovation Fund Denmark (4135-00084B), SAF2015-68346-P (Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF)) and (PI12/00156 and PI16/00287)Instituto de Salud Carlos III (Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF)). Support from the Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) (Instituto de Salud Carlos III) and Generalitat de Catalunya Grup de Recerca Consolidat, 2017SGR717 is also acknowledged.

Novel fast-acting antidepressant strategies, such as ketamine and deep brain stimulation, enhance glutamatergic neurotransmission in medial prefrontal cortex (mPFC) regions via AMPA receptor (AMPA-R) activation. We recently reported that the regionally-selective blockade of the glial glutamate transporter-1 (GLT-1) by dihydrokainic acid (DHK) microinfusion in rat infralimbic cortex (IL), the most ventral part of the mPFC, evoked immediate (10 min) antidepressant-like responses, which involved AMPA-R activation and were associated to increased serotonin (5-hydroxytryptamine, 5-HT) release. Given the reciprocal connectivity between the mPFC and the serotonergic dorsal raphe nucleus (DR), here we examined the serotoninergic mechanisms involved in the reported antidepressant-like responses of DHK microinfusion. First, we show that antidepressant-like responses evoked by IL application of DHK and citalopram are mediated by local 5-HT1A receptors (5-HT1A-R), since they are cancelled by previous IL WAY100635 microinfusion. Second, IL DHK microinfusion increases excitatory inputs onto DR, as shown by an increased glutamate and 5-HT release in DR and by a selective increase of c-Fos expression in DR 5-HT neurons, not occurring in putative GABAergic neurons. This view is also supported by an increased 5-HT release in ventral hippocampus following IL DHK microinfusion. Interestingly, antidepressant-like responses evoked by IL DHK lasted for 2 h and could be prolonged for up to 24 h by attenuating self-inhibitory effects via 5-HT1A autoreceptors. In contrast, the antidepressant-like effects of S-AMPA microinfusion in IL were short-lasting. Together, our results further support a prominent role of the IL–DR pathway and of ascending 5-HT pathways in mediating antidepressant-like responses evoked by glutamatergic mechanisms., This work was supported by the Spanish Ministry of Economy and Competitiveness (SAF2015-68346 and BES2013-063241 to J.G-C; BFU2015-68568-P to A.O.) co-financed by European Regional Development Fund; Generalitat de Catalunya (CERCA Programme; 2014-SGR798, 2016FI-B00285 to M.T-G, 2016 FI-B00531 to S.M-T and ICREA Acadèmia to A.O.); Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM).

Hallucinogens evoke sensory, perceptual, affective, and cognitive effects that may be useful to understand the neurobiological basis of mood and psychotic disorders. The present chapter reviews preclinical research carried out in recent years in order to better understand the action of psychotomimetic agents such as the noncompetitive NMDA receptor (NMDA-R) antagonists and serotonergic hallucinogens. Our studies have focused on the mechanisms through which these agents alter cortical activity. Noncompetitive NMDA-R antagonists, such as phencyclidine (PCP) and MK-801 (dizocilpine), as well as the serotonergic hallucinogens DOI and 5-MeO-DMT, produce similar effects on cellular and population activity in prefrontal cortex (PFC); these effects include alterations of pyramidal neuron discharge (with an overall increase in firing), as well as a marked attenuation of the low frequency oscillations (0.2–4 Hz) to which neuronal discharge is coupled in anesthetized rodents. PCP increases c-fos expression in excitatory neurons from various cortical and subcortical areas, particularly the thalamus. This effect of PCP involves the preferential blockade of NMDA-R on GABAergic neurons of the reticular nucleus of the thalamus, which provides feedforward inhibition to the rest of thalamic nuclei. It is still unknown whether serotonergic hallucinogens also affect thalamocortical networks. However, when examined, similar alterations in other cortical areas, such as the primary visual cortex (V1), have been observed, suggesting that these agents affect cortical activity in sensory and associative areas. Interestingly, the disruption of PFC activity induced by PCP, DOI and 5-MeO-DMT is reversed by classical and atypical antipsychotic drugs. This effect suggests a possible link between the mechanisms underlying the disruption of perception by multiple classes of hallucinogenic agents and the therapeutic efficacy of antipsychotic agents., Supported by the Innovative Medicines Initiative Joint Undertaking (IMI) under Grant Agreement N° 115008 (NEWMEDS). IMI is a public–private partnership between the European Union and the European Federation of Pharmaceutical Industries and Associations. Support from the following grants is also acknowledged: SAF 2015-68346-P (Ministry of Economy and Competitiveness and European Regional Development Fund), PI09/1245 and PI12/00156 (PN de I+D+I 2008–2011, ISCIII-Subdireccion General de Evaluación y Fomento de la Investigación cofinanced by the European Regional Development Fund. “Una manera de hacer Europa”) and Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM (P82, 11INT3). Support from the Generalitat de Catalunya (SGR20093) is also acknowledged. MR is recipient of a IDIBAPS fellowship.

Progressive neuronal death in brainstem nuclei and widespread accumulation of α-synuclein are neuropathological hallmarks of Parkinson’s disease (PD). Reduction of α-synuclein levels is therefore a potential therapy for PD. However, because α-synuclein is essential for neuronal development and function, α-synuclein elimination would dramatically impact brain function. We previously developed conjugated small interfering RNA (siRNA) sequences that selectively target serotonin (5-HT) or norepinephrine (NE) neurons after intranasal administration. Here, we used this strategy to conjugate inhibitory oligonucleotides, siRNA and antisense oligonucleotide (ASO), with the triple monoamine reuptake inhibitor indatraline (IND), to selectively reduce α-synuclein expression in the brainstem monoamine nuclei of mice after intranasal delivery. Following internalization of the conjugated oligonucleotides in monoamine neurons, reduced levels of endogenous α-synuclein mRNA and protein were found in substantia nigra pars compacta (SNc), ventral tegmental area (VTA), dorsal raphe nucleus (DR), and locus coeruleus (LC). α-Synuclein knockdown by ∼20%–40% did not cause monoaminergic neurodegeneration and enhanced forebrain dopamine (DA) and 5-HT release. Conversely, a modest human α-synuclein overexpression in DA neurons markedly reduced striatal DA release. These results indicate that α-synuclein negatively regulates monoamine neurotransmission and set the stage for the testing of non-viral inhibitory oligonucleotides as disease-modifying agents in α-synuclein models of PD., This work was supported by grant SAF2016-75797-R (to A.B.), INNPACTO Subprogram IPT-2012- 1208-300000 (to A.B.), and Retos-Colaboración Subprogram RTC-2014-2812-1 (to M.V. and A.B.); Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (ERDF), UE; grants PI13/01897 (to M.V.) and PI13/01390 (to A.B.), Fondo de Investigación Sanitaria-Instituto de Salud Carlos III (Spain), co-financed by ERDF; and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) and Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED). CERCA Programme/Generalitat de Catalunya is also acknowledged.

Major depression is a severe psychiatric syndrome with very high prevalence and socio-economic impact. Its pathophysiology is poorly known, yet several neurotransmitter systems and brain areas have been implicated. Selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRI) and serotonin and norepinephrine reuptake inhibitors (SNRI) are most used antidepressant treatments. However, these drugs show slow onset of action and limited efficacy, making necessary the use of drug augmentation strategies or more aggressive interventions. Two important observations have emerged in recent years indicating that more rapid and effective antidepressant treatments are possible. Hence, the deep brain stimulation (DBS) of ventral anterior (subgenual) cingulate cortex (Cg25) evokes rapid mood improvements in subgroups of treatment-resistant depressive patients, likely mediated by a functional remodelling of cortico-limbic circuits. On the other hand, the non-competitive NDMA receptor antagonist ketamine can also evoke rapid (e.g., 2 h) and persistent (up to 1 wk) improvements in some treatment-resistant patients. Moreover, recent preclinical observations indicate the antidepressant capacity of mGluR agents. Overall, this supports the usefulness of glutamatergic transmission as a new area in antidepressant drug development. On the monoamine side, new preclinical and clinical research should clarify the different roles played by 5-HT receptors in depression as well as the brain areas and circuits responsible for therapeutic improvement. This will lead to the synthesis of new agents blocking the serotonin (and possibly norepinephrine) transporter which will also activate or block 5-HT receptors playing respectively positive (e.g., postsynaptic 5-HT1A, 5-HT4) or negative (e.g., presynaptic 5-HT1A,/1B, 5-HT2A, 5-HT2C,5-HT3, etc.) roles in antidepressant effects., The author's research is supported by the Innovative Medicine Initiative Joint Undertaking under Grant Agreement no. 115008, of which resources are composed of EFPIA in-kind contribution and financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013). Support from the Generalitat de Catalunya (2009-SGR220) and the Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) is also acknowledged.

5-MeO-DMT is a natural hallucinogen acting as serotonin 5-HT

Recent studies have shown that serotonin2B receptor (5-HT2BR) antagonists exert opposite facilitatory and inhibitory effects on dopamine (DA) release in the medial prefrontal cortex (mPFC) and the nucleus accumbens (NAc), respectively, thereby leading to the proposal that these compounds could provide an interesting pharmacological tool for treating schizophrenia. Although the mechanisms underlying these effects remain unknown, several data in the literature suggest that 5-HT1ARs located into the mPFC could participate in this interaction. The present study, using in vivo microdialysis and electrophysiological recordings in rats, assessed this hypothesis by means of two selective 5-HT1AR (WAY 100635) and 5-HT2BR (RS 127445) antagonists. WAY 100635, administered either subcutaneously (0.16 mg/kg, s.c) or locally into the mPFC (0.1 μM), blocked the changes of mPFC and NAc DA release induced by the intraperitoneal administration of RS 127445 (0.16 mg/kg, i.p.). The administration of RS 127445 (0.16 mg/kg, i.p.) increased both dorsal raphe nucleus (DRN) 5-HT neuron firing rate and 5-HT outflow in the mPFC. Likewise, mPFC 5-HT outflow was increased following the intra-DRN injection of RS 127445 (0.032 μg/0.2 μl). Finally, intra-DRN injection of RS 127445 increased and decreased DA outflow in the mPFC and the NAc, respectively, these effects being reversed by the intra-mPFC perfusion of WAY 100635. These results demonstrate the existence of a functional interplay between mPFC 5-HT1ARs and DRN 5-HT2BRs in the control of the DA mesocorticolimbic system, and highlight the clinical interest of this interaction, as both receptors represent an important pharmacological target for the treatment of schizophrenia., This work was supported by grants from the Institut National de la Recherche et de la Santé (INSERM), Bordeaux University, the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM and grant SAF2015-68346-P (MINECO-FEDER). C. Devroye was a fellowship recipient from the International Ph.D. program in Neuropharmacology, University of Catania Medical School, Catania, Italy, during the course of this study.

Recent studies have shown that serotonin

Brexpiprazole (BREX), a recently approved antipsychotic drug in the US and Canada, improves cognitive dysfunction in animal models, by still largely unknown mechanisms. BREX is a partial agonist at 5‐HT1A and D2 receptors and antagonist at α1B- and α2C-adrenergic and 5-HT2A receptors all with a similar potency. The NMDA receptor antagonist phencyclidine (PCP), used as pharmacological model of schizophrenia, activates thalamocortical networks and decreases low frequency oscillations (LFO, Work supported by a contract Grant from Lundbeck and grants SAF2015-68346-P (MINECO, FEDER EU) and (PI1200156 and PI1600287) Instituto de Salud Carlos III (Spanish Ministry of Economy and Competitiveness), co-financed by ERDF (European Regional Development Fund), “A way to build Europe”. The contribution of the following funds is also acknowledged: 2014SGR 798 (Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya), CERCA Programme/Generalitat de Catalunya; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM.

Ketamine and deep brain stimulation produce rapid antidepressant effects in humans and rodents. An increased AMPA receptor (AMPA-R) signaling in medial prefrontal cortex (mPFC) has been suggested to mediate these responses. However, little research has addressed the direct effects of enhancing glutamate tone or AMPA-R stimulation in mPFC subdivisions. The current study investigates the behavioral and neurochemical consequences of glutamate transporter-1 (GLT-1) blockade or s-AMPA microinfusion in the infralimbic (IL) and prelimbic (PrL) cortex. Owing to the connectivity between the mPFC and raphe nuclei, the role of serotonin is also explored. The bilateral microinfusion of the depolarizing agent veratridine into IL -but not PrL- of rats evoked immediate antidepressant-like responses. The same regional selectivity was observed after microinfusion of dihydrokainic acid (DHK), a selective inhibitor of GLT-1, present in astrocytes. The DHK-evoked antidepressant-like responses appear to be mediated by an AMPA-R-driven enhancement of serotonergic activity, as (i) they were prevented by NBQX 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium salt) and mimicked by s-AMPA; (ii) DHK and s-AMPA elevated similarly extracellular glutamate in IL and PrL, although extracellular 5-HT and c-fos expression in the midbrain dorsal raphe increased only when these agents were applied in IL; and (iii) DHK antidepressant-like responses were prevented by 5-HT synthesis inhibition and mimicked by citalopram microinfusion in IL. These results indicate that an acute increase of glutamatergic neurotransmission selectively in IL triggers immediate antidepressant-like responses in rats, likely mediated by the activation of IL–raphe pathways, which then results in a fast increase of serotonergic activity., This work was supported by the Spanish Ministry of Economy and Competitiveness (grant numbers SAF2012-35183; SAF2015-68346; and BES2013-063241 to JG-C), co-financed by European Regional Development Fund (ERDF); Generalitat de Catalunya (grant number 2014-SGR798 and 2016FI-B00285 to MT-G) and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM).

Objective: In this study, we assessed the efficacy of 2 pharmacodynamically different antidepressants, citalopram (a selective serotonin reuptake inhibitor) and reboxetine (a norepinephrine reuptake inhibitor), as adjunctive therapy to risperidone and olanzapine for the treatment of negative symptoms in schizophrenia. Method: We performed a 6-month, multicenter, double-blind, randomized, placebo-controlled clinical trial. The recruitment period was from November 2008 to December 2011. The sample comprised 90 patients with a diagnosis of schizophrenia (DSM-IV criteria) who exhibited negative symptoms. The patients were recruited from 10 centers in different cities of the Spanish State. The primary efficacy measure was change in score on the negative subscale of the Positive and Negative Syndrome Scale (PANSS) between baseline and 6-month assessment. Other efficacy measures were changes in the PANSS subscales and total score, as well as the Scale for the Assessment of Negative Symptoms (SANS) subscales and total score. Results: For statistical analysis, we employed mixed-effects models. We did not find statistically significant differences between the placebo group and the 2 treatment groups at 6-month assessments for the PANSS total (P = .6511), any PANSS subscale (negative [P = .5533], positive [P = .1723], or general psychopathology [P = .2083]), or the SANS (P = .5884). Cohen d measure showed a small effect size below the 0.5 threshold for all comparisons. Conclusions: In conclusion, our results do not support adjunctive use of citalopram or reboxetine with risperidone or olanzapine for the treatment of negative symptoms in schizophrenia. (C) Copyright 2014 Physicians Postgraduate Press, Inc.

The prefrontal cortex (PFC) is involved in higher brain functions altered in schizophrenia. Classical antipsychotic drugs modulate information processing in cortico-limbic circuits via dopamine D2 receptor blockade in nucleus accumbens (NAc) whereas atypical antipsychotic drugs preferentially target cortical serotonin (5-HT) receptors. The brain networks involved in the therapeutic action of atypical drugs are not fully understood. Previous work indicated that medial PFC (mPFC) pyramidal neurons projecting to ventral tegmental area express 5-HT2A receptors suggesting that atypical antipsychotic drugs modulate dopaminergic activity distally, via 5-HT2A receptor (5-HT2A-R) blockade in PFC. Since the mPFC also projects heavily to NAc, we examined whether NAc-projecting pyramidal neurons also express 5-HT2A-R. Using a combination of retrograde tracing experiments and in situ hybridization we report that a substantial proportion of mPFC-NAc pyramidal neurons in rat brain express 5-HT2A-R mRNA in a layer- and area-specific manner (up to 68% in layer V of contralateral cingulate). The functional relevance of 5-HT2A-R to modulate mPFC-NAc projections was examined in dual-probe microdialysis experiments. The application of the preferential 5-HT2A-R agonist DOI into mPFC enhanced glutamate release locally (+66 ± 18%) and in NAc (+74 ± 12%) indicating that cortical 5-HT2A-R activation augments glutamatergic transmission in NAc. Since NAc integrates glutamatergic and dopaminergic inputs, blockade of 5-HT2A-R by atypical drugs may reduce cortical excitatory inputs onto GABAergic neurons of NAc, adding to dopamine D2 receptor blockade. Together with previous observations, the present results suggest that atypical antipsychotic drugs may control the activity of the mesolimbic pathway at cell body and terminal level., Support from grants SAF 2012-35183 (Ministry of Economy and Competitiveness; EU FEDER funds), PS09/01087 (Ministry of Health, ISCIII) and from the Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM. Support from Generalitat de Catalunya (SGR 20093) is also acknowledged. Giuseppe Mocci is recipient of a CSIC-JAE fellowship. Laura Jiménez-Sánchez is recipient of a predoctoral fellowship from IDIBAPS.