RESUMO
Three benzimidazole derivatives (13-15) have been synthetized as potential positron emission tomography (PET) imaging ligands for mGluR2 in the brain. Of these compounds, 13 exhibits potent binding affinity (IC50 = 7.6 ± 0.9 nM), positive allosteric modulator (PAM) activity (EC50 = 51.2 nM), and excellent selectivity against other mGluR subtypes (>100-fold). [11C]13 was synthesized via O-[11C]methylation of its phenol precursor 25 with [11C]methyl iodide. The achieved radiochemical yield was 20 ± 2% (n = 10, decay-corrected) based on [11C]CO2 with a radiochemical purity of >98% and molar activity of 98 ± 30 GBq/µmol EOS. Ex vivo biodistribution studies revealed reversible accumulation of [11C]13 and hepatobiliary and urinary excretions. PET imaging studies in rats demonstrated that [11C]13 accumulated in the mGluR2-rich brain regions. Pre-administration of mGluR2-selective PAM, 17 reduced the brain uptake of [11C]13, indicating a selective binding. Therefore, [11C]13 is a potential PET imaging ligand for mGluR2 in different central nervous system-related conditions.
Assuntos
Benzimidazóis/química , Encéfalo/diagnóstico por imagem , Desenho de Fármacos , Tomografia por Emissão de Pósitrons , Receptores de AMPA/análise , Animais , Benzimidazóis/síntese química , Benzimidazóis/farmacocinética , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Ligantes , Camundongos , Camundongos Knockout , Modelos Moleculares , Estrutura Molecular , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/deficiência , Relação Estrutura-Atividade , Distribuição TecidualRESUMO
Developing central synapses exhibit robust plasticity and undergo experience-dependent remodeling. Evidently, synapses in sensory systems such as auditory brainstem circuits mature rapidly to achieve high-fidelity neurotransmission for sound localization. This depends on a developmental switch in AMPAR composition from slow-gating GluA1-dominant to fast-gating GluA4-dominant, but the mechanisms underlying this switch remain unknown. We hypothesize that patterned stimuli mimicking spontaneous/sound evoked activity in the early postnatal stage drives this gating switch. We examined activity-dependent changes in evoked and miniature excitatory postsynaptic currents (eEPSCs and mEPSCs) at the calyx of Held synapse by breaking through the postsynaptic membrane at different time points following 2 min of theta burst stimulation (TBS) to afferents in mouse brainstem slices. We found the decay time course of eEPSCs accelerated, but this change was not apparent until > 30 min after TBS. Histogram analyses of the decay time constants of mEPSCs for naive and tetanized synapses revealed two populations centered around τfast ≈ 0.4 and 0.8 ms, but the relative weight of the τ0.4 population over the τ0.8 population increased significantly only in tetanized synapses. Such changes are blocked by NMDAR or mGluR1/5 antagonists or inhibitors of CaMKII, PKC and protein synthesis, and more importantly precluded in GluA4-/- synapses, suggesting GluA4 is the substrate underlying the acceleration. Our results demonstrate a novel form of plasticity working through NMDAR and mGluR activation to trigger a gating switch of AMPARs with a temporally delayed onset of expression, ultimately enhancing the development of high-fidelity synaptic transmission.
Assuntos
Potenciais Evocados Auditivos do Tronco Encefálico/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciais Pós-Sinápticos em Miniatura/fisiologia , Plasticidade Neuronal/fisiologia , Receptores de Glutamato Metabotrópico/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Sinapses/metabolismo , Corpo Trapezoide/fisiologia , Animais , Sinalização do Cálcio , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Camundongos , Proteínas do Tecido Nervoso/biossíntese , Proteína Quinase C/metabolismo , Receptores de AMPA/biossíntese , Receptores de AMPA/deficiência , Receptores de AMPA/genética , Receptores de Glutamato Metabotrópico/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Tetania/fisiopatologia , Ritmo Teta , Fatores de Tempo , Corpo Trapezoide/ultraestruturaRESUMO
Inhibitory interneurons derived from the medial ganglionic eminence represent the largest cohort of GABAergic neurons in the hippocampus. In the CA1 hippocampus excitatory synapses onto these cells comprise GluA2-lacking, calcium-permeable AMPARs. Although synaptic transmission is not established until early in their postnatal life, AMPARs are expressed early in development, however their role is enigmatic. Using the Nkx2.1-cre mouse line we genetically deleted GluA1, GluA2, GluA3 selectively from MGE derived interneurons early in development. We observed that the number of MGE-derived interneurons was preserved in mature hippocampus despite early elimination of AMPARs, which resulted in >90% decrease in spontaneous excitatory synaptic activity. Of particular interest, excitatory synaptic sites were shifted from dendritic to somatic locations while maintaining a normal NMDAR content. The developmental switch of NMDARs from GluN2B-containing early in development to GluN2A-containing on maturation was similarly unperturbed despite the loss of AMPARs. Early network giant depolarizing potential oscillatory activity was compromised in early postnatal days as was both feedforward and feedback inhibition onto pyramidal neurons underscoring the importance of glutamatergic drive onto MGE-derived interneurons for hippocampal circuit function.
Assuntos
Potenciais Pós-Sinápticos Excitadores , Deleção de Genes , Interneurônios/metabolismo , Células-Tronco Neurais/citologia , Neurogênese , Células Piramidais/metabolismo , Receptores de AMPA/deficiência , Animais , Região CA1 Hipocampal/citologia , Região CA1 Hipocampal/metabolismo , Cálcio/metabolismo , Diferenciação Celular , Interneurônios/citologia , Canais Iônicos/metabolismo , Camundongos , Camundongos Transgênicos , Células Piramidais/citologia , Receptores de AMPA/metabolismoRESUMO
Pathogenic mutations in cyclin-dependent kinase-like 5 (CDKL5) result in CDKL5 deficiency disorder (CDD), a rare disease marked by early-life seizures, autistic behaviors, and intellectual disability. Although mouse models of CDD exhibit dendritic instability and alterations in synaptic scaffolding proteins, studies of glutamate receptor levels and function are limited. Here we used a novel mouse model of CDD, the Cdkl5R59X knock-in mouse (R59X), to investigate changes in synaptic glutamate receptor subunits and functional consequences. Male mice were used for all experiments to avoid the confounding effects of X-inactivation that would be present in female heterozygous mice. We showed that adult male R59X mice recapitulated the behavioral outcomes observed in other mouse models of CDD, including social deficits and memory and learning impairments, and exhibited decreased latency to seizure upon pentylenetetrazol administration. Furthermore, we observed a specific increase in GluA2-lacking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)-type glutamate receptors (AMPARs) in the adult R59X hippocampus, which is accompanied electrophysiologically by increased rectification ratio of AMPAR EPSCs and elevated early-phase long term potentiation (LTP). Finally, we showed that acute treatment with the GluA2-lacking AMPAR blocker IEM-1460 decreased AMPAR currents, and rescued social deficits, working memory impairments, and seizure behavior latency in R59X mice.SIGNIFICANCE STATEMENT CDKL5 deficiency disorder (CDD) is a rare disease marked by autistic-like behaviors, intellectual disability, and seizures. While synaptic dysfunction has been observed in mouse models of CDD, there is limited information on how synaptic alterations contribute to behavioral and functional changes in CDD. Here we reveal elevated hippocampal GluA2-lacking AMPAR expression in a novel mouse model of CDD that is accompanied by changes in synaptic AMPAR function and plasticity. We also show, for the first time, that acutely targeting GluA2-lacking AMPAR dysregulation rescues core synaptic and neurobehavioral deficits in CDD.
Assuntos
Síndromes Epilépticas/tratamento farmacológico , Síndromes Epilépticas/genética , Proteínas Serina-Treonina Quinases/deficiência , Proteínas Serina-Treonina Quinases/genética , Receptores de AMPA/efeitos dos fármacos , Espasmos Infantis/tratamento farmacológico , Espasmos Infantis/genética , Adulto , Animais , Comportamento Animal , Pré-Escolar , Modelos Animais de Doenças , Síndromes Epilépticas/psicologia , Potenciais Pós-Sinápticos Excitadores/genética , Feminino , Técnicas de Introdução de Genes , Humanos , Deficiências da Aprendizagem/genética , Deficiências da Aprendizagem/psicologia , Masculino , Transtornos da Memória/genética , Transtornos da Memória/psicologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes Neurológicos , Mutação/genética , Desempenho Psicomotor , Receptores de AMPA/deficiência , Receptores de AMPA/genética , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Comportamento Social , Espasmos Infantis/psicologiaRESUMO
Cognitive flexibility is an important aspect of executive function. The cholinergic system, an important component of cognition, has been shown to modulate cognitive flexibility mainly through the striatum and prefrontal cortex. The role of M1 muscarinic receptors (M1 mAChRs), an important therapeutic target in the cholinergic system, in hippocampus-dependent cognitive flexibility is unclarified. In the present study, we demonstrated that selective activation of M1 mAChRs promoted extinction of initial learned response and facilitated acquisition of reversal learning in the Morris water maze, a behavior test that is mainly dependent on the hippocampus. However, these effects were abolished in GluA2 mutant mice with deficiency in phosphorylation of Ser880 by protein kinase C (PKC). Further long-term depression (LTD) in the hippocampal CA1 area induced by M1 mAChR activation was shown to be dependent on AMPA receptor subunit GluA2 but not GluA1. M1 mAChRs increased GluA2 endocytosis through phosphorylation of Ser880 by PKC. Inhibition of PKC blocked M1 mAChR-mediated LTD, memory switching and reversal learning facilitation. Moreover, the slow memory extinction observed in GluA2 mutant mice and PKC inhibitor-treated mice appeared to affect the consolidation and retrieval of reversal learning. Thus, these results demonstrate that M1 mAChRs mainly facilitate acquisition in spatial reversal learning and further elucidate that such an effect is dependent on the phosphorylation of GluA2 by PKC. The study helps clarify the role of M1 mAChRs in cognitive flexibility and may prompt the earlier prevention of cognitive inflexibility.
Assuntos
Receptor Muscarínico M1/efeitos dos fármacos , Receptor Muscarínico M1/metabolismo , Receptores de AMPA/metabolismo , Reversão de Aprendizagem/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Região CA1 Hipocampal/efeitos dos fármacos , Cognição/fisiologia , Hipocampo , Aprendizagem/fisiologia , Masculino , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fosforilação , Piperidinas , Proteína Quinase C/antagonistas & inibidores , Quinolonas , Receptor Muscarínico M1/agonistas , Receptores de AMPA/deficiênciaRESUMO
Synaptic AMPAR expression controls the strength of excitatory synaptic transmission and plasticity. An excess of synaptic AMPARs leads to epilepsy in response to seizure-inducible stimulation. The appropriate regulation of AMPARs plays a crucial role in the maintenance of the excitatory/inhibitory synaptic balance; however, the detailed mechanisms underlying epilepsy remain unclear. Our previous studies have revealed that a key modification of AMPAR trafficking to and from postsynaptic membranes is the reversible, posttranslational S-palmitoylation at the C-termini of receptors. To clarify the role of palmitoylation-dependent regulation of AMPARs in vivo, we generated GluA1 palmitoylation-deficient (Cys811 to Ser substitution) knock-in mice. These mutant male mice showed elevated seizure susceptibility and seizure-induced neuronal activity without impairments in synaptic transmission, gross brain structure, or behavior at the basal level. Disruption of the palmitoylation site was accompanied by upregulated GluA1 phosphorylation at Ser831, but not at Ser845, in the hippocampus and increased GluA1 protein expression in the cortex. Furthermore, GluA1 palmitoylation suppressed excessive spine enlargement above a certain size after LTP. Our findings indicate that an abnormality in GluA1 palmitoylation can lead to hyperexcitability in the cerebrum, which negatively affects the maintenance of network stability, resulting in epileptic seizures.SIGNIFICANCE STATEMENT AMPARs predominantly mediate excitatory synaptic transmission. AMPARs are regulated in a posttranslational, palmitoylation-dependent manner in excitatory synapses of the mammalian brain. Reversible palmitoylation dynamically controls synaptic expression and intracellular trafficking of the receptors. Here, we generated GluA1 palmitoylation-deficient knock-in mice to clarify the role of AMPAR palmitoylation in vivo We showed that an abnormality in GluA1 palmitoylation led to hyperexcitability, resulting in epileptic seizure. This is the first identification of a specific palmitoylated protein critical for the seizure-suppressing process. Our data also provide insight into how predicted receptors such as AMPARs can effectively preserve network stability in the brain. Furthermore, these findings help to define novel key targets for developing anti-epileptic drugs.
Assuntos
Hipocampo/metabolismo , Hipocampo/fisiopatologia , Palmitatos/metabolismo , Receptores de AMPA/deficiência , Convulsões/metabolismo , Convulsões/fisiopatologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Receptores de AMPA/genética , Convulsões/genéticaRESUMO
Capsaicin has been shown to modulate synaptic plasticity in various brain regions including the amygdala. Whereas in the lateral amygdala the modulatory effect of capsaicin on long-term potentiation (LA-LTP) is mediated by TRPV1 channels, we have recently shown that capsaicin-induced enhancement of long term depression (LA-LTD) is mediated by TRPM1 receptors. However, the underlying mechanism by which capsaicin modulates synaptic plasticity is poorly understood. In the present study, we investigate the modulatory effect of capsaicin on synaptic plasticity in mice lacking the AMPAR subunit GluA1. Capsaicin reduced the magnitude of LA-LTP in slices derived from wild-type mice as previously described, whereas this capsaicin-induced suppression was absent in GluA1-deficient mice. In contrast, neither LA-LTD nor the capsaicin-mediated enhancement of LA-LTD was changed in GluA1 knockout mice. Our data indicate that capsaicin-induced modulation of LA-LTP via TRPV1 involves GluA1-containing AMPARs whereas capsaicin-induced modulation of LA-LTD via TRPM1 is independent of the expression of the AMPAR GluA1 subunit.
Assuntos
Tonsila do Cerebelo/efeitos dos fármacos , Capsaicina/farmacologia , Fármacos Atuantes sobre Aminoácidos Excitatórios/farmacologia , Potenciação de Longa Duração/efeitos dos fármacos , Receptores de AMPA/metabolismo , Tonsila do Cerebelo/metabolismo , Animais , Estimulação Elétrica , Feminino , Potenciação de Longa Duração/fisiologia , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Depressão Sináptica de Longo Prazo/fisiologia , Masculino , Camundongos Knockout , Microeletrodos , Nootrópicos/farmacologia , Receptores de AMPA/deficiência , Receptores de AMPA/genética , Técnicas de Cultura de TecidosRESUMO
The GluA1 subunit of the AMPA receptor has been implicated in schizophrenia. While GluA1 is important for cognition, it is not clear what the role of GluA1 is in hedonic responses that are relevant to the negative symptoms of disorders such as schizophrenia. Here, we tested mice that lack GluA1 (Gria1 -/- mice) on consumption of sucrose solutions using a licking microstructure analysis. GluA1 deletion drastically reduced palatability (as measured by the mean lick cluster size) across a range of sucrose concentrations. Although initial lick rates were reduced, measures of consumption across long periods of access to sucrose solutions were not affected by GluA1 deletion and Gria1 -/- mice showed normal satiety responses to high sucrose concentrations. GluA1 deletion also failed to impair flavour conditioning, in which increased intake of a flavour occurred as a consequence of prior pairing with a high sucrose concentration. These results demonstrate that GluA1 plays a role in responding on the basis of palatability rather than other properties, such as the automatic and learnt post-ingestive, nutritional consequences of sucrose. Therefore, Gria1 -/- mice provide a potential model of anhedonia, adding converging evidence to the role of glutamatergic dysfunction in various symptoms of schizophrenia and related disorders.
Assuntos
Comportamento Alimentar , Subunidades Proteicas/deficiência , Receptores de AMPA/deficiência , Resposta de Saciedade , Sacarose/metabolismo , Animais , Deleção de Genes , Camundongos , Camundongos KnockoutRESUMO
AMPA glutamate receptor complexes with fast kinetics conferred by subunits like GluA3 and GluA4 are essential for temporal precision of synaptic transmission. The specific role of GluA3 in auditory processing and experience related changes in the auditory brainstem remain unknown. We investigated the role of the GluA3 in auditory processing by using wild type (WT) and GluA3 knockout (GluA3-KO) mice. We recorded auditory brainstem responses (ABR) to assess auditory function and used electron microscopy to evaluate the ultrastructure of the auditory nerve synapse on bushy cells (AN-BC synapse). Since labeling for GluA3 subunit increases on auditory nerve synapses within the cochlear nucleus in response to transient sound reduction, we investigated the role of GluA3 in experience-dependent changes in auditory processing. We induced transient sound reduction by plugging one ear and evaluated ABR threshold and peak amplitude recovery for up to 60 days after ear plug removal in WT and GluA3-KO mice. We found that the deletion of GluA3 leads to impaired auditory signaling that is reflected in decreased ABR peak amplitudes, an increased latency of peak 2, early onset hearing loss and reduced numbers and sizes of postsynaptic densities (PSDs) of AN-BC synapses. Additionally, the lack of GluA3 hampers ABR threshold recovery after transient ear plugging. We conclude that GluA3 is required for normal auditory signaling, normal ultrastructure of AN-BC synapses in the cochlear nucleus and normal experience-dependent changes in auditory processing after transient sound reduction.
Assuntos
Percepção Auditiva , Comportamento Animal , Nervo Coclear/metabolismo , Núcleo Coclear/metabolismo , Perda Auditiva de Alta Frequência/metabolismo , Audição , Receptores de AMPA/deficiência , Sinapses/metabolismo , Estimulação Acústica , Adaptação Fisiológica , Animais , Nervo Coclear/fisiopatologia , Nervo Coclear/ultraestrutura , Núcleo Coclear/fisiopatologia , Núcleo Coclear/ultraestrutura , Potenciais Evocados Auditivos do Tronco Encefálico , Predisposição Genética para Doença , Perda Auditiva de Alta Frequência/genética , Perda Auditiva de Alta Frequência/patologia , Perda Auditiva de Alta Frequência/fisiopatologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , Tempo de Reação , Receptores de AMPA/genética , Sinapses/ultraestrutura , Fatores de TempoRESUMO
Spatial working memory (SWM) is an essential cognitive function important for survival in a competitive environment. In rodents SWM requires an intact hippocampus and SWM expression is impaired in mice lacking the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 (Gria1-/- mice). Here we used viral gene transfer to show that re-expression of GluA1 in the hippocampus can affect the behavioral performance of GluA1 deficient mice. We found that Gria1-/- mice with hippocampus-specific rescue of GluA1 expression (Gria1Hpc mice) are more anxious, less hyperactive and only partly impaired in SWM expression in the Y-maze spatial novelty preference paradigm compared to Gria1-/- mice. However, Gria1Hpc mice still express SWM performance deficits when tested in the rewarded alternation T-maze task. Thus, the restoration of hippocampal function affects several behaviors of GluA1 deficient mice - including SWM expression - in different tasks. The virus-mediated GluA1 expression in Gria1-/- mice is not sufficient for a comprehensive SWM restoration, suggesting that both hippocampal as well as extra-hippocampal GluA1-containing AMPA receptors contribute to SWM.
Assuntos
Hipocampo/metabolismo , Transtornos da Memória/metabolismo , Transtornos da Memória/fisiopatologia , Memória de Curto Prazo/fisiologia , Receptores de AMPA/metabolismo , Memória Espacial/fisiologia , Animais , Comportamento Animal/fisiologia , Técnicas de Transferência de Genes , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/deficiênciaRESUMO
Development of the neuronal circuitry involves both Hebbian and homeostatic plasticity mechanisms that orchestrate activity-dependent refinement of the synaptic connectivity. AMPA receptor subunit GluA4 is expressed in hippocampal pyramidal neurons during early postnatal period and is critical for neonatal long-term potentiation; however, its role in homeostatic plasticity is unknown. Here we show that GluA4-dependent plasticity mechanisms allow immature synapses to promptly respond to alterations in network activity. In the neonatal CA3, the threshold for homeostatic plasticity is low, and a 15-h activity blockage with tetrodotoxin triggers homeostatic upregulation of glutamatergic transmission. On the other hand, attenuation of the correlated high-frequency bursting in the CA3-CA1 circuitry leads to weakening of AMPA transmission in CA1, thus reflecting a critical role for Hebbian synapse induction in the developing CA3-CA1. Both of these developmentally restricted forms of plasticity were absent in GluA4(-/-) mice. These data suggest that GluA4 enables efficient homeostatic upscaling and responsiveness to temporal activity patterns during the critical period of activity-dependent refinement of the circuitry.
Assuntos
Potenciais Pós-Sinápticos Excitadores/fisiologia , Hipocampo/citologia , Células Piramidais/fisiologia , Receptores de AMPA/deficiência , Sinapses/fisiologia , Animais , Animais Recém-Nascidos , Carbenoxolona/farmacologia , Estimulação Elétrica , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/genética , Hipocampo/crescimento & desenvolvimento , Técnicas In Vitro , Camundongos , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Técnicas de Patch-Clamp , Células Piramidais/efeitos dos fármacos , Receptores de AMPA/genética , Bloqueadores dos Canais de Sódio/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/genética , Tetrodotoxina/farmacologia , Fatores de TempoRESUMO
Addiction is a behavioral disease, of which core components can be modeled in rodents. Much evidence implicates drug-evoked synaptic plasticity in cocaine-evoked locomotor sensitization, cue-induced cocaine seeking, and incubation of cocaine craving. However, the type of plasticity evoked by different modalities of cocaine administration (eg contingent vs non-contingent) and its role in reshaping circuit function remains largely elusive. Here we exposed mice to various regimens of cocaine and recorded excitatory transmission onto identified medium-sized spiny neurons (MSN, expressing fluorescent proteins under the control of either D1R or D2R dopamine receptor promotor) in the nucleus accumbens at time points when behavioral adaptations are observed. In D1-MSN, we found the presence of GluA2-lacking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) after single or chronic non-contingent exposure to cocaine as well as after cocaine self-administration (SA). We also report an increase in the AMPA/NMDA ratio (A/N) in D1-MSN, which was observed only after repeated passive injections associated with locomotor sensitization as well as in a condition of SA leading to seeking behavior. Remarkably, insertion of GluA2-lacking AMPARs was also detected in D2-MSN after SA of a high dose of cocaine but not regular dose (1.5 vs 0.75 mg/kg), which was the only condition where incubation of cocaine craving was observed in this study. Moreover, synapses containing GluA2-lacking AMPARs belonged to amygdala inputs in D2-MSN and to medial prefrontal cortex inputs in D1-MSN. Taken together this study allows for a refinement of a circuit model of addiction based on specific synaptic changes induced by cocaine.
Assuntos
Transtornos Relacionados ao Uso de Cocaína/fisiopatologia , Cocaína/administração & dosagem , Sinais (Psicologia) , Comportamento de Procura de Droga/efeitos dos fármacos , Receptores de AMPA/deficiência , Vasoconstritores/administração & dosagem , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Encéfalo/citologia , Condicionamento Operante/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Locomoção/efeitos dos fármacos , Locomoção/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Receptores de AMPA/genética , Receptores Dopaminérgicos/deficiência , Receptores Dopaminérgicos/genética , Transdução GenéticaRESUMO
We investigated whether glutamate receptor subunit 2 (GluR2) is involved in EA pretreatment-induced neuroprotection via cannabinoid CB1 receptors (CB1R) after global cerebral ischemia in mice. Two hours after electric acupuncture (EA) pretreatment, global cerebral ischemia (GCI) was induced by bilateral common carotid artery occlusion (BCCAO) for 20â min. The GluR2 expression was examined in the hippocampus after reperfusion. Cell survival, neuronal apoptosis, the Bax/Bcl-2 ratio and neurological scores were evaluated at 24â h after BCCAO in the presence or absence of the GluR2 inhibitor. Furthermore, the GluR2 was determined in the presence and absence of CB1R inhibitor. Our results showed EA pretreatment enhanced expression of GluR2 in the hippocampus 2â h after reperfusion. Moreover, EA pretreatment improved neurological outcome, promoted cell survival, inhibited neuronal apoptosis, and decreased the Bax/Bcl-2 ratio after reperfusion. GluR2 knockdown by GluR2 siRNA effectively reversed the beneficial effects of EA pretreatment. Furthermore, CB1R siRNA and two CB1R antagonists blocked the elevation of GluR2 expression by EA pretreatment, whereas the two CB1R agonists up-regulated GluR2 expression as EA pretreatment. In conclusion, GluR2 up-regulation is involved in neuroprotection of EA pretreatment against GCI through CB1R, suggesting that GluR2 may be a novel target for stroke intervention.
Assuntos
Eletroacupuntura , Regulação da Expressão Gênica , Receptor CB1 de Canabinoide/metabolismo , Receptores de AMPA/genética , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Ácidos Araquidônicos/farmacologia , Isquemia Encefálica/genética , Isquemia Encefálica/metabolismo , Isquemia Encefálica/terapia , Sobrevivência Celular/genética , Modelos Animais de Doenças , Regulação para Baixo , Endocanabinoides/farmacologia , Técnicas de Silenciamento de Genes , Glicerídeos/farmacologia , Hipocampo/metabolismo , Camundongos , Células Piramidais/metabolismo , Interferência de RNA , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptores de AMPA/deficiência , Reperfusão , Fatores de Tempo , Regulação para CimaRESUMO
Both the glutamatergic and serotonergic (5-HT) systems are implicated in the modulation of mood and anxiety. Descending cortical glutamatergic neurons regulate 5-HT neuronal activity in the midbrain raphe nuclei through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors. To analyze the functional role of GLUA1-containing AMPA receptors in serotonergic neurons, we used the Cre-ERT2/loxP-system for the conditional inactivation of the GLUA1-encoding Gria1 gene selectively in 5-HT neurons of adult mice. These Gria1(5-HT-/-) mice exhibited a distinct anxiety phenotype but showed no alterations in locomotion, depression-like behavior, or learning and memory. Increased anxiety-related behavior was associated with significant decreases in tryptophan hydroxylase 2 (TPH2) expression and activity, and subsequent reductions in tissue levels of 5-HT, its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and norepinephrine in the raphe nuclei. However, TPH2 expression and activity as well as monoamine levels were unchanged in the projection areas of 5-HT neurons. Extracellular electrophysiological recordings of 5-HT neurons revealed that, while α1-adrenoceptor-mediated excitation was unchanged, excitatory responses to AMPA were enhanced and the 5-HT1A autoreceptor-mediated inhibitory response to 5-HT was attenuated in Gria1(5-HT-/-) mice. Our data show that a loss of GLUA1 protein in 5-HT neurons enhances AMPA receptor function and leads to multiple local molecular and neurochemical changes in the raphe nuclei that dysregulate 5-HT neuronal activity and induce anxiety-like behavior.
Assuntos
Ansiedade/fisiopatologia , Encéfalo/fisiopatologia , Receptores de AMPA/deficiência , Neurônios Serotoninérgicos/fisiologia , Animais , Depressão/fisiopatologia , Ácido Hidroxi-Indolacético/metabolismo , Aprendizagem/fisiologia , Masculino , Memória/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Norepinefrina/metabolismo , Fenótipo , Receptores de AMPA/genética , Receptores Adrenérgicos alfa 1/metabolismo , Serotonina/metabolismo , Triptofano Hidroxilase/metabolismoRESUMO
Malfunction of glutamate transmission is implicated in several neuropsychiatric disorders. Gria1-/- mouse line with knocked-out GluA1 subunits of ionotropic AMPA glutamate receptor displays several behavioural features of schizoaffective disorder. Typically, these mice show hyperactivity provoked by environmental novelty, which is attenuated after 4-week treatment with the standard mood-stabilisers lithium and valproate and the mood-stabilising anticonvulsants topiramate and lamotrigine (Maksimovic, M., Vekovischeva, O.Y., Aitta-Aho, T., Korpi, E.R., 2014. Chronic treatment with mood-stabilizers attenuates abnormal hyperlocomotion of GluA1-subunit deficient mice. PloS One. 9, e100188). Here, we complement our study by treating these mice chronically with perampanel, a novel non-competitive antagonist of AMPA receptors, for 4 weeks at the dose of 60 mg/kg diet, and found reduced locomotor hyperactivity in the Gria1-/- animals, while not affecting the wild-type littermates. To study the cellular mechanism by which chronic treatments with glutamate-modulating mood-stabilizing drugs alleviate this hyperactivity, we used the immediate early gene c-Fos protein expression as a marker of neuronal activity in the brain. Chronic lithium, valproate and topiramate blunted the c-Fos expression especially in the dorsal hippocampus of the Gria1-/- mice, with all of them reducing the number of c-Fos-positive cells in the CA3 region and valproate and topiramate also in the dentate gyrus (DG). Lamotrigine and perampanel treatments had the same effect in the all CA1, CA3 and DG subfields of the dorsal hippocampus of Gria1-/- mice. The results suggest that abnormal (hippocampal) glutamatergic transmission underlies the hyperactive phenotype of the Gria1-/- mice in a novel environment, and based on the efficacies of the present chronic drug treatments, this mouse model may serve as a predictive tool for studying novel mood-stabilisers.
Assuntos
Comportamento Exploratório/fisiologia , Hipocampo/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptores de AMPA/deficiência , Animais , Região CA3 Hipocampal/efeitos dos fármacos , Região CA3 Hipocampal/metabolismo , Comportamento Exploratório/efeitos dos fármacos , Feminino , Frutose/administração & dosagem , Frutose/análogos & derivados , Ácido Glutâmico/metabolismo , Hipocampo/efeitos dos fármacos , Lamotrigina , Compostos de Lítio/administração & dosagem , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Fármacos Neuroprotetores/administração & dosagem , Nitrilas , Piridonas/administração & dosagem , Receptores de AMPA/antagonistas & inibidores , Receptores de AMPA/genética , Receptores de AMPA/metabolismo , Transmissão Sináptica , Topiramato , Triazinas/administração & dosagem , Ácido Valproico/administração & dosagemRESUMO
At hippocampal synapses, activation of group I metabotropic glutamate receptors (mGluRs) induces long-term depression (LTD), which requires new protein synthesis. However, the underlying mechanism remains elusive. Here we describe the translational program that underlies mGluR-LTD and identify the translation factor eIF2α as its master effector. Genetically reducing eIF2α phosphorylation, or specifically blocking the translation controlled by eIF2α phosphorylation, prevented mGluR-LTD and the internalization of surface AMPA receptors (AMPARs). Conversely, direct phosphorylation of eIF2α, bypassing mGluR activation, triggered a sustained LTD and removal of surface AMPARs. Combining polysome profiling and RNA sequencing, we identified the mRNAs translationally upregulated during mGluR-LTD. Translation of one of these mRNAs, oligophrenin-1, mediates the LTD induced by eIF2α phosphorylation. Mice deficient in phospho-eIF2α-mediated translation are impaired in object-place learning, a behavioral task that induces hippocampal mGluR-LTD in vivo. Our findings identify a new model of mGluR-LTD, which promises to be of value in the treatment of mGluR-LTD-linked cognitive disorders.
Assuntos
Fator de Iniciação 2 em Eucariotos/genética , Fator de Iniciação 2 em Eucariotos/metabolismo , Aprendizagem/fisiologia , Depressão Sináptica de Longo Prazo/genética , Biossíntese de Proteínas , Receptores de AMPA/fisiologia , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Regulação da Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fosforilação/genética , Receptores de AMPA/deficiência , Percepção Espacial/fisiologiaRESUMO
Glutamatergic dysfunctions have recently been postulated to play a considerable role in mood disorders. However, molecular mechanisms underlying these effects have been poorly deciphered. Previous work demonstrated the contribution of GluA1-containing AMPA receptors (AMPAR) to a depression-like and anxiety-like phenotype. Here we investigated the effect of temporally and spatially restricted gene manipulation of GluA1 on behavioural correlates of mood disorders in mice. Here we show that tamoxifen-induced GluA1 deletion restricted to forebrain glutamatergic neurons of post-adolescent mice does not induce depression- and anxiety-like changes. This differs from the phenotype of mice with global AMPAR deletion suggesting that for mood regulation AMPAR may be particularly important on inhibitory interneurons or already early in development.
Assuntos
Regulação da Expressão Gênica/genética , Desamparo Aprendido , Transtornos do Humor/patologia , Neurônios/metabolismo , Prosencéfalo/metabolismo , Receptores de AMPA/deficiência , Análise de Variância , Animais , Modelos Animais de Doenças , Comportamento Exploratório/fisiologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Transgênicos , Transtornos do Humor/genética , Prosencéfalo/patologia , Tempo de Reação/fisiologia , Receptores de AMPA/genética , Tamoxifeno/farmacologiaRESUMO
Cornichon2 (CNIH2), an integral component of AMPA receptor (AMPAR) complexes in the mammalian brain, slows deactivation and desensitization of heterologously reconstituted receptor channels. Its significance in neuronal signal transduction, however, has remained elusive. Here we show by paired recordings that CNIH2-containing AMPARs dictate the slow decay of excitatory postsynaptic currents (EPSCs) elicited in hilar mossy cells of the hippocampus by single action potentials in mossy fiber boutons (MFB). Selective knockdown of CNIH2 markedly accelerated EPSCs in individual MFB-mossy cell synapses without altering the EPSC amplitude. In contrast, the rapidly decaying EPSCs in synapses between MFBs and aspiny interneurons that lack expression of CNIH2 were unaffected by the protein knockdown but were slowed by virus-directed expression of CNIH2. These results identify CNIH2 as the molecular distinction between slow and fast EPSC phenotypes and show that CNIH2 influences the time course and, hence, the efficacy of excitatory synaptic transmission.
Assuntos
Potenciais Pós-Sinápticos Excitadores/fisiologia , Hipocampo/citologia , Neurônios/citologia , Receptores de AMPA/fisiologia , Sinapses/fisiologia , Animais , Estimulação Elétrica , Regulação da Expressão Gênica/genética , Técnicas In Vitro , Camundongos , Camundongos Transgênicos , Neurônios/ultraestrutura , Técnicas de Patch-Clamp , Ratos , Ratos Wistar , Receptores de AMPA/química , Receptores de AMPA/deficiência , Receptores de AMPA/genética , Frações Subcelulares/metabolismo , Frações Subcelulares/ultraestrutura , Fatores de TempoRESUMO
The hippocampus and the parahippocampal region have been proposed to contribute to path integration. Mice lacking GluA1-containing AMPA receptors (GluA1(-/-) mice) were previously shown to exhibit impaired hippocampal place cell selectivity. Here we investigated whether path integration performance and the activity of grid cells of the medial entorhinal cortex (MEC) are affected in these mice. We first tested GluA1(-/-) mice on a standard food-carrying homing task and found that they were impaired in processing idiothetic cues. To corroborate these findings, we developed an L-maze task that is less complex and is performed entirely in darkness, thereby reducing numerous confounding variables when testing path integration. Also in this task, the performance of GluA1(-/-) mice was impaired. Next, we performed in vivo recordings in the MEC of GluA1(-/-) mice. MEC neurons exhibited altered grid cell spatial periodicity and reduced spatial selectivity, whereas head direction tuning and speed modulation were not affected. The firing associations between pairs of neurons in GluA1(-/-) mice were stable, both in time and space, indicating that attractor states were still present despite the lack of grid periodicity. Together, these results support the hypothesis that spatial representations in the hippocampal-entorhinal network contribute to path integration.
Assuntos
Córtex Entorrinal/citologia , Comportamento de Retorno ao Território Vital/fisiologia , Neurônios/fisiologia , Periodicidade , Receptores de AMPA/deficiência , Comportamento Espacial/fisiologia , Estimulação Acústica , Potenciais de Ação/genética , Animais , Mapeamento Encefálico , Análise por Conglomerados , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Transgênicos , Modelos Neurológicos , Vias Neurais/fisiologia , Receptores de AMPA/genética , Percepção Espacial/fisiologia , Ritmo Teta , Fatores de TempoRESUMO
Glutamate is the most abundant excitatory neurotransmitter in the brain, and distinct classes of glutamate receptors coordinate synaptic transmission and spike generation upon various levels of neuronal activity. However, the mechanisms remain unclear. Here, we found that loss of synaptic AMPA receptors increased kainate receptor activity in cerebellar granule cells without changing NMDA receptors. The augmentation of kainate receptor-mediated currents in the absence of AMPA receptor activity is required for spike generation and is mediated by the increased expression of the GluK5 high-affinity kainate receptor subunit. Increase in GluK5 expression is sufficient to enhance kainate receptor activity by modulating receptor channel properties, but not localization. Furthermore, we demonstrate that the combined loss of the AMPA receptor auxiliary TARPγ-2 subunit and the GluK5 subunit leads to early mouse lethality. Our findings reveal mechanisms mediated by distinct classes of postsynaptic glutamate receptors for the homeostatic maintenance of the neuronal activity.