Criticality supports cross-frequency cortical-thalamic information transfer during conscious states.

Consciousness is thought to be regulated by bidirectional information transfer between the cortex and thalamus, but the nature of this bidirectional communication - and its possible disruption in unconsciousness - remains poorly understood. Here, we present two main findings elucidating mechanisms of corticothalamic information transfer during conscious states. First, we identify a highly preserved spectral channel of cortical-thalamic communication that is present during conscious states, but which is diminished during the loss of consciousness and enhanced during psychedelic states. Specifically, we show that in humans, mice, and rats, information sent from either the cortex or thalamus via δ/θ/α waves (∼1-13 Hz) is consistently encoded by the other brain region by high γ waves (52-104 Hz); moreover, unconsciousness induced by propofol anesthesia or generalized spike-and-wave seizures diminishes this cross-frequency communication, whereas the psychedelic 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) enhances this low-to-high frequency interregional communication. Second, we leverage numerical simulations and neural electrophysiology recordings from the thalamus and cortex of human patients, rats, and mice to show that these changes in cross-frequency cortical-thalamic information transfer may be mediated by excursions of low-frequency thalamocortical electrodynamics toward/away from edge-of-chaos criticality, or the phase transition from stability to chaos. Overall, our findings link thalamic-cortical communication to consciousness, and further offer a novel, mathematically well-defined framework to explain the disruption to thalamic-cortical information transfer during unconscious states.

Lu AF35700 reverses the phencyclidine-induced disruption of thalamo-cortical activity by blocking dopamine D1 and D2 receptors.

Antipsychotic drugs of different chemical/pharmacological families show preferential dopamine (DA) D2 receptor (D2-R) vs. D1 receptor (D1-R) affinity, with the exception of clozapine, the gold standard of schizophrenia treatment, which shows a comparable affinity for both DA receptors. Here, we examined the ability of Lu AF35700 (preferential D1-R>D2-R antagonist), to reverse the alterations in thalamo-cortical activity induced by phencyclidine (PCP), used as a pharmacological model of schizophrenia. Lu AF35700 reversed the PCP-induced alteration of neuronal discharge and low frequency oscillation (LFO, 0.15-4 Hz) in thalamo-cortical networks. Likewise, Lu AF35700 prevented the increased c-fos mRNA expression induced by PCP in thalamo-cortical regions of awake rats. We next examined the contribution of D1-R and D2-R to the antipsychotic reversal of PCP effects. The D2-R antagonist haloperidol reversed PCP effects on thalamic discharge rate and LFO. Remarkably, the combination of sub-effective doses of haloperidol and SCH-23390 (DA D1-R antagonist) fully reversed the PCP-induced fall in thalamo-cortical LFO. However, unlike with haloperidol, SCH-23390 elicited different degrees of potentiation of the effects of low clozapine and Lu AF35700 doses. Overall, the present data support a synergistic interaction between both DA receptors to reverse the PCP-induced alterations of oscillatory activity in thalamo-cortical networks, possibly due to their simultaneous blockade in direct and indirect pathways of basal ganglia. The mild potentiation induced by SCH-23390 in the case of clozapine and Lu AF35700 suggests that, at effective doses, these agents reverse PCP effects through the simultaneous blockade of both DA receptors.

Differential Modulation of Dorsal Raphe Serotonergic Activity in Rat Brain by the Infralimbic and Prelimbic Cortices.

The reciprocal connectivity between the medial prefrontal cortex (mPFC) and the dorsal raphe nucleus (DR) is involved in mood control and resilience to stress. The infralimbic subdivision (IL) of the mPFC is the rodent equivalent of the ventral anterior cingulate cortex, which is intimately related to the pathophysiology/treatment of major depressive disorder (MDD). Boosting excitatory neurotransmission in the IL-but not in the prelimbic cortex, PrL-evokes depressive-like or antidepressant-like behaviors in rodents, which are associated with changes in serotonergic (5-HT) neurotransmission. We therefore examined the control of 5-HT activity by both of the mPFC subdivisions in anesthetized rats. The electrical stimulation of IL and PrL at 0.9 Hz comparably inhibited 5-HT neurons (53% vs. 48%, respectively). However, stimulation at higher frequencies (10-20 Hz) revealed a greater proportion of 5-HT neurons sensitive to IL than to PrL stimulation (86% vs. 59%, at 20 Hz, respectively), together with a differential involvement of GABAA (but not 5-HT1A) receptors. Likewise, electrical and optogenetic stimulation of IL and PrL enhanced 5-HT release in DR in a frequency-dependent manner, with greater elevations after IL stimulation at 20 Hz. Hence, IL and PrL differentially control serotonergic activity, with an apparent superior role of IL, an observation that may help to clarify the brain circuits involved in MDD.

iPSC-based modeling of THD recapitulates disease phenotypes and reveals neuronal malformation.

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 neurite arborization defects, which were not evident in DAn differentiated from control-iPSC. 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.

Preferential In Vivo Inhibitory Action of Serotonin in Rat Infralimbic versus Prelimbic Cortex: Relevance for Antidepressant Treatments.

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.

Ketamine triggers rapid antidepressant effects by modulating synaptic plasticity in a new depressive-like mouse model based on astrocyte glutamate transporter GLT-1 knockdown in infralimbic cortex.

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.

Differential expression of serotonin2B receptors in GABAergic and serotoninergic neurons of the rat and mouse dorsal raphe nucleus.

The central serotonin2B receptor (5-HT2BR) modulates 5-HT and dopamine (DA) neuronal function in the mammalian brain and has been suggested as a potential target for the treatment of neuropsychiatric disorders involving derangements of these monoamine systems, such as schizophrenia, cocaine abuse and dependence and major depressive disorder. Studies in rats and mice yielded contrasting results on the control of 5-HT/DA networks by 5-HT2BRs, thereby leading to opposite views on the therapeutic potential of 5-HT2BR agents for treating the above disorders. These discrepancies may result from anatomo-functional differences related to a different cellular location of 5-HT2BRs in rat and mouse brain. Using immunohistochemistry, we assessed this hypothesis by examining the expression of 5-HT2BRs in 5-HT and GABAergic neurons of rats and mice within different subregions of the dorsal raphe nucleus (DRN), currently considered as the main site of action of 5-HT2B agents. Likewise, using in vivo microdialysis, we examined their functional relevance in the control of DRN 5-HT outflow, a surrogate index of 5-HT neuronal activity. In the DRN of both species, 5-HT2BRs are expressed in 5-HT cells expressing tryptophan hydroxylase 2 (TPH2), in GABAergic cells expressing glutamic acid decarboxylase 67 (GAD67), and in cells expressing both markers (GAD67 & TPH2; i.e., GABA-expressing 5-HT neurons). The proportion of 5-HT2BR-positive cells expressing only TPH2 was significantly larger in mouse than in rat DRN, whereas the opposite holds true for the expression in cells expressing GAD67 & TPH2. No major species differences were found in the dorsal and ventral subregions. In contrast, the lateral subregion exhibited large differences, with a predominant expression of 5-HT2BRs in TPH2-positive cells in mice (67.2 vs 19.9 % in rats), associated with a lower expression in GAD67 & TPH2 cells (7.9 % in mice vs 41.5 % in rats). Intra-DRN (0.1 µM) administration of the preferential 5-HT2BR agonist BW 723C86 decreased and increased DRN 5-HT outflow in rats and mice respectively, both effects being prevented by the intra-DRN perfusion of the selective 5-HT2BR antagonist RS 127445 (0.1 µM). Altogether, these results show the existence of anatomical differences in the cellular expression of 5-HT2BRs in the rat and mouse DRN, which translate into an opposite control of 5-HT outflow. Also, they highlight the relevance of the subset of GAD67-positive 5-HT neurons as a key factor responsible for the functional differences between rats and mice in terms of 5-HT neuronal activity modulation.

Discrimination of motor and sensorimotor effects of phencyclidine and MK-801: Involvement of GluN2C-containing NMDA receptors in psychosis-like models.

Non-competitive NMDA receptor (NMDA-R) antagonists like ketamine, phencyclidine (PCP) and MK-801 are routinely used as pharmacological models of schizophrenia. However, the NMDA-R subtypes, neuronal types (e.g., GABA vs. glutamatergic neurons) and brain regions involved in psychotomimetic actions are not fully understood. PCP activates thalamo-cortical circuits after NMDA-R blockade in reticular thalamic GABAergic neurons. GluN2C subunits are densely expressed in thalamus and cerebellum. Therefore, we examined their involvement in the behavioral and functional effects elicited by PCP and MK-801 using GluN2C knockout (GluN2CKO) and wild-type mice, under the working hypothesis that psychotomimetic effects should be attenuated in mutant mice. PCP and MK-801 induced a disorganized and meandered hyperlocomotion in both genotypes. Interestingly, stereotyped behaviors like circling/rotation, rearings and ataxia signs were dramatically reduced in GluN2CKO mice, indicating a better motor coordination in absence of GluN2C subunits. In contrast, other motor or sensorimotor (pre-pulse inhibition of the startle response) aspects of the behavioral syndrome remained unaltered by GluN2C deletion. PCP and MK-801 evoked a general pattern of c-fos activation in mouse brain (including thalamo-cortical networks) but not in the cerebellum, where they markedly reduced c-fos expression, with significant genotype differences paralleling those in motor coordination. Finally, resting-state fMRI showed an enhanced cortico-thalamic-cerebellar connectivity in GluN2CKO mice, less affected by MK-801 than controls. Hence, the GluN2C subunit allows the dissection of the behavioral alterations induced by PCP and MK-801, showing that some motor effects (in particular, motor incoordination), but not deficits in sensorimotor gating, likely depend on GluN2C-containing NMDA-R blockade in cerebellar circuits.

Ketamine triggers rapid antidepressant effects by modulating synaptic plasticity in a new depressive-like mouse model based on astrocyte glutamate transporter GLT-1 knockdown in infralimbic cortex / La ketamina desencadena efectos antidepresivos rápidos en un nuevo modelo de ratón con fenotipo depresivo basado en la reducción del transportador de glutamato de astrocitos GLT-1 en la corteza infralímbica mediante la modulación de la plasticidad sináptica

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.(AU)

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. (AU)

Human α-synuclein overexpression in mouse serotonin neurons triggers a depressive-like phenotype. Rescue by oligonucleotide therapy.

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.

Dual 5-HT3 and 5-HT6 Receptor Antagonist FPPQ Normalizes Phencyclidine-Induced Disruption of Brain Oscillatory Activity in Rats.

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-399 885, 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.

Oligonucleotides as therapeutic tools for brain disorders: Focus on major depressive disorder and Parkinson's disease.

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.

Intracerebral Administration of a Ligand-ASO Conjugate Selectively Reduces α-Synuclein Accumulation in Monoamine Neurons of Double Mutant Human A30P*A53T*α-Synuclein Transgenic Mice.

α-Synuclein (α-Syn) protein is involved in the pathogenesis of Parkinson's disease (PD). Point mutations and multiplications of the α-Syn, which encodes the SNCA gene, are correlated with early-onset PD, therefore the reduction in a-Syn synthesis could be a potential therapy for PD if delivered to the key affected neurons. Several experimental strategies for PD have been developed in recent years using oligonucleotide therapeutics. However, some of them have failed or even caused neuronal toxicity. One limiting step in the success of oligonucleotide-based therapeutics is their delivery to the brain compartment, and once there, to selected neuronal populations. Previously, we developed an indatraline-conjugated antisense oligonucleotide (IND-1233-ASO), that selectively reduces α-Syn synthesis in midbrain monoamine neurons of mice, and nonhuman primates. Here, we extended these observations using a transgenic male mouse strain carrying both A30P and A53T mutant human α-Syn (A30P*A53T*α-Syn). We found that A30P*A53T*α-Syn mice at 4-5 months of age showed 3.5-fold increases in human α-Syn expression in dopamine (DA) and norepinephrine (NE) neurons of the substantia nigra pars compacta (SNc) and locus coeruleus (LC), respectively, compared with mouse α-Syn levels. In parallel, transgenic mice exhibited altered nigrostriatal DA neurotransmission, motor alterations, and an anxiety-like phenotype. Intracerebroventricular IND-1233-ASO administration (100 µg/day, 28 days) prevented the α-Syn synthesis and accumulation in the SNc and LC, and recovered DA neurotransmission, although it did not reverse the behavioral phenotype. Therefore, the present therapeutic strategy based on a conjugated ASO could be used for the selective inhibition of α-Syn expression in PD-vulnerable monoamine neurons, showing the benefit of the optimization of ASO molecules as a disease modifying therapy for PD and related α-synucleinopathies.

Involvement of NMDA receptors containing the GluN2C subunit in the psychotomimetic and antidepressant-like effects of ketamine.

Acute ketamine administration evokes rapid and sustained antidepressant effects in treatment-resistant patients. However, ketamine also produces transient perceptual disturbances similarly to those evoked by other non-competitive NMDA-R antagonists like phencyclidine (PCP). Although the brain networks involved in both ketamine actions are not fully understood, PCP and ketamine activate thalamo-cortical networks after NMDA-R blockade in GABAergic neurons of the reticular thalamic nucleus (RtN). Given the involvement of thalamo-cortical networks in processing sensory information, these networks may underlie psychotomimetic action. Since the GluN2C subunit is densely expressed in the thalamus, including the RtN, we examined the dependence of psychotomimetic and antidepressant-like actions of ketamine on the presence of GluN2C subunits, using wild-type and GluN2C knockout (GluN2CKO) mice. Likewise, since few studies have investigated ketamine's effects in females, we used mice of both sexes. GluN2C deletion dramatically reduced stereotyped (circling) behavior induced by ketamine in male and female mice, while the antidepressant-like effect was fully preserved in both genotypes and sexes. Despite ketamine appeared to induce similar effects in both sexes, some neurobiological differences were observed between male and female mice regarding c-fos expression in thalamic nuclei and cerebellum, and glutamate surge in prefrontal cortex. In conclusion, the GluN2C subunit may discriminate between antidepressant-like and psychotomimetic actions of ketamine. Further, the abundant presence of GluN2C subunits in the cerebellum and the improved motor coordination of GluN2CKO mice after ketamine treatment suggest the involvement of cerebellar NMDA-Rs in some behavioral actions of ketamine.

M2 cortex-dorsolateral striatum stimulation reverses motor symptoms and synaptic deficits in Huntington's disease.

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.

Serotonin2B receptor blockade in the rat dorsal raphe nucleus suppresses cocaine-induced hyperlocomotion through an opposite control of mesocortical and mesoaccumbens dopamine pathways.

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) 3ß 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 GSK3ß 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.

Sub-chronic vortioxetine (but not escitalopram) normalizes brain rhythm alterations and memory deficits induced by serotonin depletion in rats.

Major depressive disorder (MDD) is a chronic and disabling psychiatric disorder characterized by a wide range of signs/symptoms, including cognitive dysfunction. Vortioxetine (VOR) is a multimodal antidepressant drug with pro-cognitive actions in animal models and MDD patients. The VOR-mediated blockade of 5-HT3-R in a subpopulation of GABA interneurons enhances pyramidal neuron activity in rat medial prefrontal cortex, an effect possibly underlying its pro-cognitive action. Brain oscillations are involved in regulation of cognitive function. We therefore examined VOR effects on oscillatory activity in four brain areas of freely-moving rats (prelimbic cortex, PrL; nucleus accumbens, NAc; dorsal hippocampus, dHPC; paraventricular thalamic nucleus, PVA), in standard and in serotonin-depleted rats showing recognition memory deficits. 4-chloro-dl-phenylalanine (pCPA) markedly reduced low frequency oscillations (LFO, mainly 1 Hz oscillations) and enhanced theta oscillations in PrL and NAc. It also reduced gamma and high frequency oscillations (HFO) in PVA. Subchronic VOR and escitalopram (ESC) treatments had little effect on oscillatory activity in standard rats. However, VOR -but not ESC- prevented recognition memory deficits in 5-HT-depleted rats, and normalized LFO and theta powers in PrL and NAc. In parallel, VOR -but not ESC- prevented the deficit in PrL-dHPC gamma coherence, but not the decrease in gamma and HFO powers in PVA. Overall, this supports a prominent role of serotonergic neurotransmission on brain oscillatory activity, particularly in cortico-striatal pathways linked to short-term recognition memory. Further, VOR prevented pCPA-induced cognitive deficits by normalizing oscillatory activity at lower frequencies in the PrL-NAc pathway, also normalizing the PrL-dHPC coherence at gamma frequencies.

Anti-α-synuclein ASO delivered to monoamine neurons prevents α-synuclein accumulation in a Parkinson's disease-like mouse model and in monkeys.

BACKGROUND: 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. METHODS: 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. FINDINGS: 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. CONCLUSIONS: 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. FUNDING: 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).