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

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

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

The natural hallucinogen 5-MeO-DMT, component of Ayahuasca, disrupts cortical function in rats: reversal by antipsychotic drugs

5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural hallucinogen component of Ayahuasca, an Amazonian beverage traditionally used for ritual, religious and healing purposes that is being increasingly used for recreational purposes in US and Europe. 5MeO-DMT is of potential interest for schizophrenia research owing to its hallucinogenic properties. Two other psychotomimetic agents, phencyclidine and 2,5-dimethoxy-4-iodo-phenylisopropylamine (DOI), markedly disrupt neuronal activity and reduce the power of low frequency cortical oscillations (<4 Hz, LFCO) in rodent medial prefrontal cortex (mPFC). Here we examined the effect of 5-MeO-DMT on cortical function and its potential reversal by antipsychotic drugs. Moreover, regional brain activity was assessed by blood-oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). 5-MeO-DMT disrupted mPFC activity, increasing and decreasing the discharge of 51 and 35% of the recorded pyramidal neurons, and reducing (−31%) the power of LFCO. The latter effect depended on 5-HT1A and 5-HT2A receptor activation and was reversed by haloperidol, clozapine, risperidone, and the mGlu2/3 agonist LY379268. Likewise, 5-MeO-DMT decreased BOLD responses in visual cortex (V1) and mPFC. The disruption of cortical activity induced by 5-MeO-DMT resembles that produced by phencyclidine and DOI. This, together with the reversal by antipsychotic drugs, suggests that the observed cortical alterations are related to the psychotomimetic action of 5-MeO-DMT. Overall, the present model may help to understand the neurobiological basis of hallucinations and to identify new targets in antipsychotic drug development

Modulación de receptores serotoninérgicos corticales por psicofármacos. Implicaciones en esquizofrenia y depresión

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The serotonergic hallucinogen 5-methoxy-N,N-dimethyltryptamine disrupts cortical activity in a regionally-selective manner via 5-HT1A and 5-HT2A receptors

© 2015 Elsevier Ltd. 5-Methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a natural hallucinogen, acting as a non-selective serotonin 5-HT1A/5-HT2A-R agonist. Psychotomimetic agents such as the non-competitive NMDA-R antagonist phencyclidine and serotonergic hallucinogens (DOI and 5-MeO-DMT) disrupt cortical synchrony in the low frequency range (<4 Hz) in rat prefrontal cortex (PFC), an effect reversed by antipsychotic drugs. Here we extend these observations by examining the effect of 5-MeO-DMT on low frequency cortical oscillations (LFCO, <4 Hz) in PFC, visual (V1), somatosensory (S1) and auditory (Au1) cortices, as well as the dependence of these effects on 5-HT1A-R and 5-HT2A-R, using wild type (WT) and 5-HT2A-R knockout (KO2A) anesthetized mice. 5-MeO-DMT reduced LFCO in the PFC of WT and KO2A mice. The effect in KO2A mice was fully prevented by the 5-HT1A-R antagonist WAY-100635. Systemic and local 5-MeO-DMT reduced 5-HT release in PFC mainly via 5-HT1A-R. Moreover, 5-MeO-DMT reduced LFCO in S1, Au1 and V1 of WT mice and only in V1 of KO2A mice, suggesting the involvement of 5-HT1A-R activation in the 5-MeO-DMT-induced disruption of V1 activity. In addition, antipsychotic drugs reversed 5-MeO-DMT effects in WT mice. The present results suggest that the hallucinogen action of 5-MeO-DMT is mediated by simultaneous alterations of the activity of sensory (S1, Au1, V1) and associative (PFC) cortical areas, also supporting a role of 5-HT1A-R stimulation in V1 and PFC, in addition to the well-known action on 5-HT2A-R. Moreover, the reversal by antipsychotic drugs of 5-MeO-DMT effects adds to previous literature supporting the usefulness of the present model in antipsychotic drug development.This work was supported by grants from Instituto de Salud Carlos III (PI09/1245 (P.C.), PI12/00156 (P.C.) and PI13/01390 (A.B.) (PN de I+D+I 2008-2011, ISCIII-Subdirección General de Evaluación y Fomento de la Investigación cofinanced by the European Regional Development Fund. “Una manera de hacer Europa”), SAF 2012-35183 (Spanish Ministry of Economy and Competitiveness, co-financed by European Regional Development Fund (ERDF), Centro de Investigación Biomédica en Red de Salud Mental, (CIBERSAM P82, 11INT3) and 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 Generalitat de Catalunya (2014 SGR798) is also acknowledged. MR was supported by a IDIBAPS fellowshipPeer Reviewe

El alucinógeno 5-MeO-DMT reduce las oscilaciones lentas (<4Hz) en corteza prefrontal. Reversión por fármacos antipsicóticos

Trabajo presentado al XIV Congreso Nacional de la Sociedad Española de Neurociencia celebrado del 28 al 30 de septiembre de 2011.[Objetivos]: Estudiar la base neurobiológica de las alucinaciones usando el alucinógeno natural 5-MeO-DMT (componente de Ayahuasca, infusión amazónica), su acción sobre la actividad de la corteza prefrontal (CPF) y la posible reversión de sus efectos por fármacos antipsicóticos. La 5-MeO-DMT actúa como agonista de los receptores de serotonina 5-HT1A/5-HT2A. Su interés en el estudio de la esquizofrenia reside en su capacidad de mimetizar síntomas psicóticos , tales como las alucinaciones. [Material y Métodos]: Registros extracelular unitario de neuronas piramidales y de potencial de campo en CPF medial de rata anestesiada. Administración intravenosa de fármacos. Evaluamos la acción de la 5-MeO-DMT en presencia de clorgilina (inhibidor de la MAO-A, para evitar su rápida degradación hepática) y la posible reversión de sus efectos por antipsicóticos (haloperidol, clozapina, risperidona) y por agonistas selectivos de los receptores 5-HT1A (WAY100635) y 5-HT2A (M100907) así como por el agonista glutamatérgico mGlu 2/3LYL-379268. [Resultados]: La administración de 5-MeO-DMT (0.1 mg/kg) altera la frecuencia de descarga de las neuronas piramidales de CPF (53% excitaciones, 34% inhibiciones, 13 % no efecto; n=42) y reduce (-36%) las oscilaciones de baja frecuencia (slow cortical oscillations, -SCO-). La administración posterior de los antipsicóticos clozapina y haloperidol revierten los efectos de la 5-MeO-DMT sobre la frecuencia de descarga. La reducción en las SCO inducida por la 5-MeO-DMT es revertida por WAY100635 y por M100907. Los antipsicóticos haloperidol, clozapina y risperidona así como el agonista mGlu2/3LY379268 también revierten los efectos de la 5-MeO-DMT sobre las SCO. [Conclusiones]: Los resultados obtenidos se añaden a trabajos previos de nuestro laboratorio 1,2 en los que se muestra que agentes alucinógenos usados como modelos farmacológicos de esquizofrenia (fenciclidina-antagonista del receptor NMDA - y DOI-agonista 5-HT2A/2C-) alteran la sincronía cortical en el rango de las oscilaciones de baja frecuencia (<4Hz) en la CPF. Esto sugiere que la reducción en las SCO es una característica común a la acción de los alucinógenos. La reversión de estos efectos por fármacos antipsicóticos con diferentes mecanismos de acción, sugiere una clara asociación con su capacidad terapéutica, independientemente de la diana receptorial inicial. Estos datos apoyan la utilidad del modelo de registro de las SCO en corteza prefrontal para examinar las bases neurobiológicas de las alucinaciones y para la identificación de nuevas dianas terapéuticas en el desarrollo de fármacos antipsicóticos.Financiación: FIS PI09/1245, CIBERSAM (11INT3) y EU grant NEWMEDS (IMI; Innovative Medicines Initiative).Peer Reviewe

Subchronic vortioxetine treatment -but not escitalopram- enhances pyramidal neuron activity in the rat prefrontal cortex

Trabajo presentado en la American Psychiatric Association (APA) 169th Annual Meeting, celebrado en Atlanta, Georgia, Estados Unidos, del 14 al 18 de mayo de 2016Peer Reviewe

The hallucinogen 5-methoxy-N,Ndimethyltryptamine (5-MeO-DMT) disrupts cortical function: reversal by antipsychotic drugs

Póster presentado en el 2013 ECNP Workshop on Neuropsychopharmacology for Young Scientists in Euope, celebrado del 7 al 10 de marzo de 2013 en Nice (Francia)Abstract publicado en: European Neuropsychopharmacology 23(Suppl. 1): S40-41 (2013). ISSN: 0924-977X. e-ISSN: 1873-7862. DOI: 10.1016/S0924-977X(13)70045-2Peer Reviewe