Involvement of 5-HT3 receptors in the action of vortioxetine in rat brain: focus on glutamatergic and GABAergic neurotransmission

The antidepressant vortioxetine is a 5-HT3-R, 5-HT7-R and 5-HT1D-R antagonist, 5-HT1B-R partial agonist, 5-HT1A-R agonist, and serotonin (5-HT) transporter (SERT) inhibitor. Vortioxetine occupies all targets at high therapeutic doses and only SERT and 5-HT3-R at low doses. Vortioxetine increases extracellular monoamine concentrations in rat forebrain more than selective serotonin reuptake inhibitors (SSRI) and shows pro-cognitive activity in preclinical models. Given its high affinity for 5-HT3-R (Ki = 3.7 nM), selectively expressed in GABA interneurons, we hypothesized that vortioxetine may disinhibit glutamatergic and monoaminergic neurotransmission following 5-HT3-R blockade. Here we assessed vortioxetine effect on pyramidal neuron activity and extracellular 5-HT concentration using in vivo extracellular recordings of rat medial prefrontal cortex (mPFC) pyramidal neurons and microdialysis in mPFC and ventral hippocampus (vHPC). Vortioxetine, but not escitalopram, increased pyramidal neuron discharge in mPFC. This effect was prevented by SR57227A (5-HT3-R agonist) and was mimicked by ondansetron (5-HT3-R antagonist) and by escitalopram/ondansetron combinations. In microdialysis experiments, ondansetron augmented the 5-HT-enhancing effect of escitalopram in mPFC and vHPC. Local ondansetron in vHPC augmented escitalopram effect, indicating the participation of intrinsic mechanisms. Since 5-HT neurons express GABAB receptors, we examined their putative involvement in controlling 5-HT release after 5-HT3-R blockade. Co-perfusion of baclofen (but not muscimol) reversed the increased 5-HT levels produced by vortioxetine and escitalopram/ondansetron combinations in vHPC. The present results suggest that vortioxetine increases glutamatergic and serotonergic neurotransmission in rat forebrain by blocking 5-HT3 receptors in GABA interneurons.This work was supported by a grant from Lundbeck A/S and by grants SAF 2012-35183 and SAF 2015-68346-P from the Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF) and grant PI12/00156 (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, (2014SGR798) is also acknowledged. FA and PC are PI and co-PI from a grant from Lundbeck A/S to examine the mechanism of action of vortioxetine. FA has also received lecture and consultation fees from Lundbeck A/S and is scientific advisor to Neurolixis. CS is a Lundbeck A/S employee.Peer reviewe

Clozapine reverses phencyclidine-induced desynchronization of prefrontal cortex through a 5-HT 1A receptor-dependent mechanism

The non-competitive NMDA receptor (NMDA-R) antagonist phencyclidine (PCP) - used as a pharmacological model of schizophrenia - disrupts prefrontal cortex (PFC) activity. PCP markedly increased the discharge rate of pyramidal neurons and reduced slow cortical oscillations (SCO; 0.15-4 Hz) in rat PFC. Both effects were reversed by classical (haloperidol) and atypical (clozapine) antipsychotic drugs. Here we extended these observations to mice brain and examined the potential involvement of 5-HT 2A and 5-HT 1A receptors (5-HT 2AR and 5-HT 1AR, respectively) in the reversal by clozapine of PCP actions. Clozapine shows high in vitro affinity for 5-HT 2AR and behaves as partial agonist in vivo at 5-HT 1AR. We used wild-type (WT) mice and 5-HT 1AR and 5-HT 2AR knockout mice of the same background (C57BL/6) (KO-1A and KO-2A, respectively). Local field potentials (LFPs) were recorded in the PFC of WT, KO-1A, and KO-2A mice. PCP (10 mg/kg, intraperitoneally) reduced SCO equally in WT, KO-2A, and KO-1A mice (58±4%, 42±7%, and 63±7% of pre-drug values, n = 23, 13, 11, respectively; p < 0.0003). Clozapine (0.5 mg/kg, intraperitoneally) significantly reversed PCP effect in WT and KO-2A mice, but not in KO-1A mice nor in WT mice pretreated with the selective 5-HT 1AR antagonist WAY-100635.The PCP-induced disorganization of PFC activity does not appear to depend on serotonergic function. However, the lack of effect of clozapine in KO-1A mice and the prevention by WAY-100635 indicates that its therapeutic action involves 5-HT 1AR activation without the need to block 5-HT 2AR, as observed with clozapine-induced cortical dopamine release. © 2012 American College of Neuropsychopharmacology. All rights reserved.The work leading to these results has received funding from the Innovative Medicines Initiative Joint Undertaking (IMI) under Grant Agreement No. 115008 (NEWMEDS). This work was supported by Instituto de Salud Carlos III, Centro de Investigacion Biomedica en Red de Salud Mental (CIBERSAM) and Grants SAF 2007-62378, FIS PI09/1245 (PN de I + D + I 2008-2011, ISCIII-Subdireccion General de Evaluacion y Fomento de la Investigacion), CIBERSAM (P82, 11INT3), and SENY Fundacio. PC is supported by the Researcher Stabilization Program of the Health Department of the Generalitat de Catalunya. LK was recipient of a predoctoral fellowship from the Ministry of Science and Education.Peer Reviewe

Subchronic vortioxetine enhances cortical activity

Vortioxetine (VOR) is a multimodal antidepressant drug. VOR is a 5-HT3-R, 5-HT7-R and 5-HT1D-R antagonist, 5-HT1B-R partial agonist, 5-HT1A-R agonist, and serotonin transporter (SERT) inhibitor. VOR shows pro-cognitive activity in animal models and beneficial effects on cognitive dysfunction in major depressive patients. Here we compared the effects of 14-day treatments with VOR and escitalopram (ESC, selective serotonin reuptake inhibitor) on neuronal activity in the medial prefrontal cortex (mPFC). Ten groups of rats (5 standard, 5 depleted of 5-HT with p-chlorophenylalanine-pCPA-, used as model of cognitive impairment) were fed with control food or with two doses of VOR-containing food. Four groups were implanted with minipumps delivering vehicle or ESC 10 mg/kg·day s.c. The two VOR doses enable occupation by VOR of SERT+5-HT3-R and all targets, respectively, and correspond to SERT occupancies in patients treated with 5 and 20 VOR mg/day, respectively. Putative pyramidal neurons (n=985) were recorded extracellularly in the mPFC of anesthetized rats. Sub-chronic VOR administration (but not ESC) significantly increased neuronal discharge in standard and 5-HT-depleted conditions, with a greater effect of the low VOR dose in standard rats. VOR increased neuronal discharge in infralimbic (IL) and prelimbic (PrL) cortices. Hence, oral VOR doses evoking SERT occupancies similar to those in treated patients increase mPFC neuronal discharge. The effect in 5-HT-depleted rats cannot be explained by an antagonist action of VOR at 5-HT3-R and suggests a non-canonical interaction of VOR with 5-HT3-R. These effects may underlie the superior pro-cognitive efficacy of VOR compared with SSRIs in animal modelsSupported by Lundbeck A/S and grants: SAF2015-68346-P (Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF)) and PI12/00156 (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, 2014SGR798 is also acknowledgedPeer reviewe

Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 micro-deletion syndrome – a study in male mice

Background: The hemizygous 22q11.2 micro-deletion is a common copy number variant in humans. The deletion confers high risk of neurodevelopmental disorders including autism and schizophrenia. Up to 41% of deletion carriers experience psychotic symptoms. Methods: We present a new mouse model (Df(h22q11)/+) of the deletion syndrome (22q11.2DS) and report on the most comprehensive study undertaken in 22q11.2DS models. The study was conducted in male mice. Results: We found elevated post-pubertal NMDA receptor antagonist induced hyper-locomotion, age-independent prepulse inhibition (PPI) deficits and increased acoustic startle response (ASR). The PPI deficit and increased ASR was resistant to antipsychotic treatment. The PPI deficit was not a consequence of impaired hearing measured by auditory brain stem responses. The Df(h22q11)/+ mice also displayed increased amplitude of loudness-dependent auditory evoked potentials. Prefrontal cortex and dorsal striatal (DStr) elevations of the dopamine metabolite DOPAC and increased DStr expression of the AMPA receptor subunit GluR1 was found. The Df(h22q11)/+ mice did not deviate from wild-type mice in a wide range of other behavioural and biochemical assays. Limitations: The 22q11.2 micro-deletion has incomplete penetrance in humans and the severity of disease depends on the complete genetic makeup in concert with environmental factors. In order to obtain more marked phenotypes reflecting the severe conditions related to 22q11.2DS it is suggested to expose the Df(h22q11)/+ mice to environmental stressors which may unmask latent psychopathology. Conclusion: The Df(h22q11)/+ model will be a valuable tool for increasing our understanding of the aetiology of schizophrenia and other psychiatric disorders associated with the 22q11DS.The research leading to these results was conducted as part of NEWMEDS and received support from the Innovative Medicine Initiative Joint Undertaking under grant agreement n° 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). This work was further supported by grants from the Danish Advanced Technology Foundation (File no. 001-2009-2) and by the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM)

A mouse model of the 15q13.3 microdeletion syndrome shows prefrontal neurophysiological dysfunctions and attentional impairment.

RATIONALE: A microdeletion at locus 15q13.3 is associated with high incidence rates of psychopathology, including schizophrenia. A mouse model of the 15q13.3 microdeletion syndrome has been generated (Df[h15q13]/+) with translational utility for modelling schizophrenia-like pathology. Among other deficits, schizophrenia is characterised by dysfunctions in prefrontal cortical (PFC) inhibitory circuitry and attention. OBJECTIVES: The objective of this study is to assess PFC-dependent functioning in the Df(h15q13)/+ mouse using electrophysiological, pharmacological, and behavioural assays. METHOD: Experiments 1-2 investigated baseline firing and auditory-evoked responses of PFC interneurons and pyramidal neurons. Experiment 3 measured pyramidal firing in response to intra-PFC GABAA receptor antagonism. Experiments 4-6 assessed PFC-dependent attentional functioning through the touchscreen 5-choice serial reaction time task (5-CSRTT). Experiments 7-12 assessed reversal learning, paired-associate learning, extinction learning, progressive ratio, trial-unique non-match to sample, and object recognition. RESULTS: In experiments 1-3, the Df(h15q13)/+ mouse showed reduced baseline firing rate of fast-spiking interneurons and in the ability of the GABAA receptor antagonist gabazine to increase the firing rate of pyramidal neurons. In assays of auditory-evoked responses, PFC interneurons in the Df(h15q13)/+ mouse had reduced detection amplitudes and increased detection latencies, while pyramidal neurons showed increased detection latencies. In experiments 4-6, the Df(h15q13)/+ mouse showed a stimulus duration-dependent decrease in percent accuracy in the 5-CSRTT. The impairment was insensitive to treatment with the partial α7nAChR agonist EVP-6124. The Df(h15q13)/+ mouse showed no cognitive impairments in experiments 7-12. CONCLUSION: The Df(h15q13)/+ mouse has multiple dysfunctions converging on disrupted PFC processing as measured by several independent assays of inhibitory transmission and attentional function.The research leading to these results has received support from the Innovative Medicine Initiative Joint Undertaking under grant agreement n° 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). The Behavioural and Clinical Neuroscience Institute is co-funded by the Medical Research Council and the Wellcome Trust. This study was also supported by the Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM). The authors would like to thank Mercedes Nuñez, Noemí Jurado, Edita Bulovaitė, Sueda Tunçak, Lewis Buss, and Diab Ali for skillful technical assistance.This is the final version of the article. It first appeared from Springer via https://doi.org/10.1007/s00213-016-4265-

Actividad cortical (EEG) en modelos de esquizofrenia: A) Identificación de biomarcadores; B) Modelos para la validación de dianas y agentes terapéuticos

Comunicación presentada en el: XV Congreso Nacional de Psiquiatría, celebrado del 8 al 11 de noviembre de 2011, en Oviedo (España)Peer Reviewe

Modulación de la neurotransmisión glutamatérgica por fármacos antipsicóticos: Nuevas dianas

Comunicación presentada en: Nuevos Abordajes en el Tratamiento de la Esquizofrenia : II Foro Internacional, celebrado los días 28 y 29 de noviembre de 2013 en Madrid (España)Peer Reviewe

Serotonergic control of prefrontal cortex

Introduction and development: The prefrontal cortex (PFC) plays a crucial role in higher brain functions such as working memory or cognition and controls, via the excitatory axons of pyramidal neurons, the activity of many subcortical motor and limbic areas. It receives a dense innervation from the brainstem aminergic nuclei, including the serotonergic raphe nuclei. Prefrontal function and metabolism is altered in patients with severe psychiatric disorders, like major depression or schizophrenia. Although the exact role of serotonergic neurotransmission in PFC remains largely unknown, the PFC contains a very large density or serotonin 5-HT1A (inhibitory) and 5-HT2A (excitatory) receptors. In addition, hallucinogens like LSD or DOI are agonists and atypical antipsychotics are antagonists at 5-HT2A receptors. In this review we focus on the main excitatory and inhibitory mechanisms through which serotonin modulates pyramidal and GABAergic neuron activity in the PFC. CONCLUSIONS: We report on the presence of 5-HT1A and 5-HT2A receptor-mediated responses in pyramidal neurons of the PFC that exert opposite effects on their activity when recorded in vivo in the anesthetized rat. Despite the large co-expression of both receptors in pyramidal neurons of the PFC, physiological amounts of 5-HT mainly inhibit pyramidal neurons. This is probably due to the distinct location of 5-HT1A and 5-HT2A in pyramidal neurons. Thus, 5-HT1A receptors are mainly localized in the axon hillock, where they may have a prominent inhibitory role in the control of pyramidal activity given their coupling to GIRK channels. Moreover, 5-HT can inhibit pyramidal neurons indirectly through the activation of 5-HT2A and 5-HT3 receptors localized in GABAergic interneurons and a subsequent increase in synaptic GABA inputs.Peer reviewedSerotoni

Monoamine oxidase inhibitors increase preferentially extracellular 5-hydroxytryptamine in the midbrain raphe nuclei. A brain microdialysis study in the awake rat

The final publication is available at www.springerlink.comWe have examined the local and systemic effects of clorgyline, tranylcypromine and deprenyl on extracellular serotonin (5-HT) and 5-hydroxyindoleacetic acid in the raphe nuclei and in frontal cortex of awake, freely-moving rats using microdialysis. When administered through the dialysis probe, monoamine oxidase (monoamine: oxygen oxidoreductase (deaminating), E.C. 1.4.3.4., MAO) inhibitors increased 5-HT output in a dose-dependent manner in both brain areas. The effects were more pronounced in the raphe nuclei for the three MAO inhibitors at all doses assayed. When the monoamine oxidase inhibitors were given i.p., dialysate 5-HT increased dramatically, after tranylcypromine (15 mg/kg), in raphe nuclei and frontal cortex (area under the curve (AUC) to 4 h post-treatment: 63-fold and 11-fold, respectively) whereas the effects of clorgyline (10 mg/kg) were much less pronounced (+ 47% increase in the AUC for raphe nuclei, P These results indicate that: (a) deamination by MAO participates actively in the control of the extracellular concentration of 5-HT in those areas of the brain that are rich in serotoninergic nerve terminals as well as in cell bodies, (b) in vivo, brain 5-HT is deaminated preferentially by MAO-A but its full inhibition does not result in an increased release of 5-HT, in spite of a large accumulation of 5-HT in the brain tissue, (c) MAO-B deaminates 5-HT when the A-form is inhibited (in this situation, MAO-B participates actively in the control of a releasable pool of 5-HT), (d) the raphe nuclei appears to be a preferential site of action of MAO inhibitors, administered either locally or systemically. These results may help to understand the model of action of MAO inhibitors as antidepressant drugs.Peer reviewe

Plasma 5-hydroxyindoleacetic acid as an indicator of MAO-A inhibition in brain and peripheral tissues

We have examined the changes induced by the monoamine oxidase (MAO; EC 1.4.3.4) inhibitors tranylcypromine, clorgyline, and deprenyl on MAO activity and 5-hydroxytryptamine (serotonin, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) content in rat brain and blood (plasma and whole blood). The decreases of MAO-A activity observed in the liver and lungs after different doses of clorgyline or tranylcypromine correlated significantly (r > 0.80 in all cases) with the decline of plasma 5-HIAA. This was unaffected by 0.25 and 5 mg kg−1 of deprenyl, indicating that 5-HT was deaminated exclusively in the periphery by MAO-A. It is interesting that very potent and significant correlations (r > 0.75) were found between plasma 5-HIAA and MAO-A activity, 5-HIAA and 5-HT content in brain tissue. These results suggest that plasma 5-HIAA can be used confidently as a peripheral indicator of the inhibition of MAO-A in brain. This may represent a favorable alternative to the analysis of 5-HIAA in CSF in psychiatric patients undergoing antidepressant treatment with nonspecific MAO inhibitors or with the new selective MAO-A inhibitors.Peer reviewe