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1.
Int J Mol Sci ; 22(8)2021 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-33918982

RESUMO

Lithium (Li+) salt is widely used as a therapeutic agent for treating neurological and psychiatric disorders. Despite its therapeutic effects on neurological and psychiatric disorders, it can also disturb the neuroendocrine axis in patients under lithium therapy. The hypothalamic area contains GABAergic and glutamatergic neurons and their receptors, which regulate various hypothalamic functions such as the release of neurohormones, control circadian activities. At the neuronal level, several neurotransmitter systems are modulated by lithium exposure. However, the effect of Li+ on hypothalamic neuron excitability and the precise action mechanism involved in such an effect have not been fully understood yet. Therefore, Li+ action on hypothalamic neurons was investigated using a whole-cell patch-clamp technique. In hypothalamic neurons, Li+ increased the GABAergic synaptic activities via action potential independent presynaptic mechanisms. Next, concentration-dependent replacement of Na+ by Li+ in artificial cerebrospinal fluid increased frequencies of GABAergic miniature inhibitory postsynaptic currents without altering their amplitudes. Li+ perfusion induced inward currents in the majority of hypothalamic neurons independent of amino-acids receptor activation. These results suggests that Li+ treatment can directly affect the hypothalamic region of the brain and regulate the release of various neurohormones involved in synchronizing the neuroendocrine axis.


Assuntos
Neurônios GABAérgicos/efeitos dos fármacos , Neurônios GABAérgicos/metabolismo , Lítio/farmacologia , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Animais , Humanos , Hipotálamo/metabolismo , Hipotálamo/patologia , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Técnicas de Patch-Clamp , Área Pré-Óptica/efeitos dos fármacos , Área Pré-Óptica/metabolismo , Receptores de Aminoácido/metabolismo , Transmissão Sináptica/efeitos dos fármacos
2.
Nat Commun ; 12(1): 2380, 2021 04 22.
Artigo em Inglês | MEDLINE | ID: mdl-33888718

RESUMO

Diverse signaling complexes are precisely assembled at the presynaptic active zone for dynamic modulation of synaptic transmission and synaptic plasticity. Presynaptic GABAB-receptors nucleate critical signaling complexes regulating neurotransmitter release at most synapses. However, the molecular mechanisms underlying assembly of GABAB-receptor signaling complexes remain unclear. Here we show that neurexins are required for the localization and function of presynaptic GABAB-receptor signaling complexes. At four model synapses, excitatory calyx of Held synapses in the brainstem, excitatory and inhibitory synapses on hippocampal CA1-region pyramidal neurons, and inhibitory basket cell synapses in the cerebellum, deletion of neurexins rendered neurotransmitter release significantly less sensitive to GABAB-receptor activation. Moreover, deletion of neurexins caused a loss of GABAB-receptors from the presynaptic active zone of the calyx synapse. These findings extend the role of neurexins at the presynaptic active zone to enabling GABAB-receptor signaling, supporting the notion that neurexins function as central organizers of active zone signaling complexes.


Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Moléculas de Adesão de Célula Nervosa/metabolismo , Receptores de GABA-B/metabolismo , Sinapses/metabolismo , Animais , Tronco Encefálico/citologia , Tronco Encefálico/metabolismo , Região CA1 Hipocampal/citologia , Região CA1 Hipocampal/fisiologia , Região CA3 Hipocampal/citologia , Região CA3 Hipocampal/metabolismo , Proteínas de Ligação ao Cálcio/genética , Cerebelo/citologia , Cerebelo/metabolismo , Camundongos , Camundongos Knockout , Modelos Animais , Proteínas do Tecido Nervoso/genética , Moléculas de Adesão de Célula Nervosa/genética , Plasticidade Neuronal/fisiologia , Técnicas de Patch-Clamp , Células Piramidais/metabolismo , Técnicas Estereotáxicas , Transmissão Sináptica/fisiologia , Ácido gama-Aminobutírico/metabolismo
3.
Int J Mol Sci ; 22(6)2021 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-33804598

RESUMO

We previously introduced the brain erythropoietin (EPO) circle as a model to explain the adaptive 'brain hardware upgrade' and enhanced performance. In this fundamental circle, brain cells, challenged by motor-cognitive tasks, experience functional hypoxia, triggering the expression of EPO among other genes. We attested hypoxic cells by a transgenic reporter approach under the ubiquitous CAG promoter, with Hif-1α oxygen-dependent degradation-domain (ODD) fused to CreERT2-recombinase. To specifically focus on the functional hypoxia of excitatory pyramidal neurons, here, we generated CaMKIIα-CreERT2-ODD::R26R-tdTomato mice. Behavioral challenges, light-sheet microscopy, immunohistochemistry, single-cell mRNA-seq, and neuronal cultures under normoxia or hypoxia served to portray these mice. Upon complex running wheel performance as the motor-cognitive task, a distinct increase in functional hypoxic neurons was assessed immunohistochemically and confirmed three-dimensionally. In contrast, fear conditioning as hippocampal stimulus was likely too short-lived to provoke neuronal hypoxia. Transcriptome data of hippocampus under normoxia versus inspiratory hypoxia revealed increases in CA1 CaMKIIα-neurons with an immature signature, characterized by the expression of Dcx, Tbr1, CaMKIIα, Tle4, and Zbtb20, and consistent with accelerated differentiation. The hypoxia reporter response was reproduced in vitro upon neuronal maturation. To conclude, task-associated activity triggers neuronal functional hypoxia as a local and brain-wide reaction mediating adaptive neuroplasticity. Hypoxia-induced genes such as EPO drive neuronal differentiation, brain maturation, and improved performance.


Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , Cognição , Expressão Gênica , Hipóxia/genética , Hipóxia/metabolismo , Neurônios/metabolismo , Animais , Encéfalo/fisiologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Hipóxia Celular/efeitos dos fármacos , Células Cultivadas , Biologia Computacional , Relação Dose-Resposta a Droga , Imunofluorescência , Perfilação da Expressão Gênica , Genes Reporter , Imuno-Histoquímica , Camundongos , Camundongos Transgênicos , Neurônios/efeitos dos fármacos , Células Piramidais/metabolismo , Tamoxifeno/farmacologia , Transcriptoma
4.
Int J Mol Sci ; 22(8)2021 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-33921375

RESUMO

It has been studied that the damage or death of neurons in the hippocampus is different according to hippocampal subregions, cornu ammonis 1-3 (CA1-3), after transient ischemia in the forebrain, showing that pyramidal neurons located in the subfield CA1 (CA1) are most vulnerable to this ischemia. Hyperthermia is a proven risk factor for brain ischemia and can develop more severe and extensive brain damage related with mortality rate. It is well known that heme oxygenase-1 (HO-1) activity and expression is increased by various stimuli in the brain, including hyperthermia. HO-1 can be either protective or deleterious in the central nervous system, and its roles depend on the expression levels of enzymes. In this study, we investigated the effects of hyperthermia during ischemia on HO-1 expression and neuronal damage/death in the hippocampus to examine the relationship between HO-1 and neuronal damage/death following 5-min transient ischemia in the forebrain using gerbils. Gerbils were assigned to four groups: (1) sham-operated gerbils with normothermia (Normo + sham group); (2) ischemia-operated gerbils with normothermia (Normo + ischemia group); (3) sham-operated gerbils with hyperthermia (39.5 ± 0.2 °C) during ischemia (Hyper + sham group); and (4) ischemia-operated gerbils with hyperthermia during ischemia (Hyper + ischemia group). HO-1 expression levels in CA1-3 of the Hyper + ischemia group were significantly higher than those in the Normo + ischemia group. HO-1 immunoreactivity in the Hyper + ischemia group was significantly increased in pyramidal neurons and astrocytes with time after ischemia, and the immunoreactivity was significantly higher than that in the Normo + ischemia group. In the Normo + Ischemia group, neuronal death was shown in pyramidal neurons located only in CA1 at 5 days after ischemia. However, in the Hyper + ischemia group, pyramidal neuronal death occurred in CA1-3 at 2 days after ischemia. Taken together, our findings showed that brain ischemic insult during hyperthermic condition brings up earlier and severer neuronal damage/death in the hippocampus, showing that HO-1 expression in neurons and astrocytes is different according to brain subregions and temperature condition. Based on these findings, we suggest that hyperthermia in patients with ischemic stroke must be taken into the consideration in the therapy.


Assuntos
Lesões Encefálicas/genética , Heme Oxigenase-1/genética , Hipocampo/metabolismo , Traumatismo por Reperfusão/genética , Animais , Astrócitos/metabolismo , Astrócitos/patologia , Lesões Encefálicas/metabolismo , Lesões Encefálicas/patologia , Gerbillinae/genética , Gerbillinae/metabolismo , Hipocampo/lesões , Hipocampo/fisiopatologia , Células Piramidais/metabolismo , Células Piramidais/patologia , Traumatismo por Reperfusão/patologia
5.
Br J Anaesth ; 126(6): 1141-1156, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33641936

RESUMO

BACKGROUND: Both animal and retrospective human studies have linked extended and repeated general anaesthesia during early development with cognitive and behavioural deficits later in life. However, the neuronal circuit mechanisms underlying this anaesthesia-induced behavioural impairment are poorly understood. METHODS: Neonatal mice were administered one or three doses of propofol, a commonly used i.v. general anaesthetic, over Postnatal days 7-11. Control mice received Intralipid® vehicle injections. At 4 months of age, the mice were subjected to a series of behavioural tests, including motor learning. During the process of motor learning, calcium activity of pyramidal neurones and three classes of inhibitory interneurones in the primary motor cortex were examined in vivo using two-photon microscopy. RESULTS: Repeated, but not a single, exposure of neonatal mice to propofol i.p. caused motor learning impairment in adulthood, which was accompanied by a reduction of pyramidal neurone number and activity in the motor cortex. The activity of local inhibitory interneurone networks was also altered: somatostatin-expressing and parvalbumin-expressing interneurones were hypoactive, whereas vasoactive intestinal peptide-expressing interneurones were hyperactive when the mice were performing a motor learning task. Administration of low-dose pentylenetetrazol to attenuate γ-aminobutyric acid A receptor-mediated inhibition or CX546 to potentiate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-subtype glutamate receptor function during emergence from anaesthesia ameliorated neuronal dysfunction in the cortex and prevented long-term behavioural deficits. CONCLUSIONS: Repeated exposure of neonatal mice to propofol anaesthesia during early development causes cortical circuit dysfunction and behavioural impairments in later life. Potentiation of neuronal activity during recovery from anaesthesia reduces these adverse effects of early-life anaesthesia.


Assuntos
Anestésicos Intravenosos/toxicidade , Comportamento Animal/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos dos fármacos , Atividade Motora/efeitos dos fármacos , Córtex Motor/efeitos dos fármacos , Síndromes Neurotóxicas/etiologia , Propofol/toxicidade , Animais , Animais Recém-Nascidos , Sinalização do Cálcio/efeitos dos fármacos , Teste de Labirinto em Cruz Elevado , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas GABAérgicos/farmacologia , Interneurônios/efeitos dos fármacos , Interneurônios/metabolismo , Camundongos Transgênicos , Córtex Motor/metabolismo , Córtex Motor/fisiopatologia , Inibição Neural/efeitos dos fármacos , Síndromes Neurotóxicas/fisiopatologia , Síndromes Neurotóxicas/prevenção & controle , Síndromes Neurotóxicas/psicologia , Teste de Campo Aberto/efeitos dos fármacos , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Comportamento Social
6.
Int J Mol Sci ; 22(4)2021 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-33546429

RESUMO

Inside hippocampal circuits, neuroplasticity events that individual cells may undergo during synaptic transmissions occur in the form of Long-Term Potentiation (LTP) and Long-Term Depression (LTD). The high density of NMDA receptors expressed on the surface of the dendritic CA1 spines confers to hippocampal CA3-CA1 synapses the ability to easily undergo NMDA-mediated LTP and LTD, which is essential for some forms of explicit learning in mammals. Providing a comprehensive kinetic model that can be used for running computer simulations of the synaptic transmission process is currently a major challenge. Here, we propose a compartmentalized kinetic model for CA3-CA1 synaptic transmission. Our major goal was to tune our model in order to predict the functional impact caused by disease associated variants of NMDA receptors related to severe cognitive impairment. Indeed, for variants Glu413Gly and Cys461Phe, our model predicts negative shifts in the glutamate affinity and changes in the kinetic behavior, consistent with experimental data. These results point to the predictive power of this multiscale viewpoint, which aims to integrate the quantitative kinetic description of large interaction networks typical of system biology approaches with a focus on the quality of a few, key, molecular interactions typical of structural biology ones.


Assuntos
Região CA1 Hipocampal/metabolismo , Modelos Biológicos , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/metabolismo , Transmissão Sináptica , Algoritmos , Relação Dose-Resposta a Droga , Glutamatos/metabolismo , Glutamatos/farmacologia , Simulação de Dinâmica Molecular , Mutação , Plasticidade Neuronal/fisiologia , Conformação Proteica , Células Piramidais/metabolismo , Receptores de AMPA/química , Receptores de AMPA/genética , Receptores de Glutamato/metabolismo , Receptores de N-Metil-D-Aspartato/química , Receptores de N-Metil-D-Aspartato/genética , Relação Estrutura-Atividade , Potenciais Sinápticos
7.
eNeuro ; 8(1)2021.
Artigo em Inglês | MEDLINE | ID: mdl-33531369

RESUMO

The medial entorhinal cortex (mEC) shows a high degree of spatial tuning, predominantly grid cell activity, which is reliant on robust, dynamic inhibition provided by local interneurons (INs). In fact, feedback inhibitory microcircuits involving fast-spiking parvalbumin (PV) basket cells (BCs) are believed to contribute dominantly to the emergence of grid cell firing in principal cells (PrCs). However, the strength of PV BC-mediated inhibition onto PrCs is not uniform in this region, but high in the dorsal and weak in the ventral mEC. This is in good correlation with divergent grid field sizes, but the underlying morphologic and physiological mechanisms remain unknown. In this study, we examined PV BCs in layer (L)2/3 of the mEC characterizing their intrinsic physiology, morphology and synaptic connectivity in the juvenile rat. We show that while intrinsic physiology and morphology are broadly similar over the dorsoventral axis, PV BCs form more connections onto local PrCs in the dorsal mEC, independent of target cell type. In turn, the major PrC subtypes, pyramidal cell (PC) and stellate cell (SC), form connections onto PV BCs with lower, but equal probability. These data thus identify inhibitory connectivity as source of the gradient of inhibition, plausibly explaining divergent grid field formation along this dorsoventral axis of the mEC.


Assuntos
Córtex Entorrinal , Parvalbuminas , Potenciais de Ação , Animais , Córtex Entorrinal/metabolismo , Retroalimentação , Interneurônios/metabolismo , Parvalbuminas/metabolismo , Células Piramidais/metabolismo , Ratos
8.
Int J Mol Sci ; 22(2)2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33467450

RESUMO

Fear extinction requires coordinated neural activity within the amygdala and medial prefrontal cortex (mPFC). Any behavior has a transcriptomic signature that is modified by environmental experiences, and specific genes are involved in functional plasticity and synaptic wiring during fear extinction. Here, we investigated the effects of optogenetic manipulations of prelimbic (PrL) pyramidal neurons and amygdala gene expression to analyze the specific transcriptional pathways associated to adaptive and maladaptive fear extinction. To this aim, transgenic mice were (or not) fear-conditioned and during the extinction phase they received optogenetic (or sham) stimulations over photo-activable PrL pyramidal neurons. At the end of behavioral testing, electrophysiological (neural cellular excitability and Excitatory Post-Synaptic Currents) and morphological (spinogenesis) correlates were evaluated in the PrL pyramidal neurons. Furthermore, transcriptomic cell-specific RNA-analyses (differential gene expression profiling and functional enrichment analyses) were performed in amygdala pyramidal neurons. Our results show that the optogenetic activation of PrL pyramidal neurons in fear-conditioned mice induces fear extinction deficits, reflected in an increase of cellular excitability, excitatory neurotransmission, and spinogenesis of PrL pyramidal neurons, and associated to strong modifications of the transcriptome of amygdala pyramidal neurons. Understanding the electrophysiological, morphological, and transcriptomic architecture of fear extinction may facilitate the comprehension of fear-related disorders.


Assuntos
Tonsila do Cerebelo/fisiologia , Condicionamento Clássico/fisiologia , Extinção Psicológica/fisiologia , Medo/fisiologia , Células Piramidais/fisiologia , Transcriptoma/genética , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/metabolismo , Animais , Fenômenos Eletrofisiológicos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Medo/psicologia , Masculino , Memória/fisiologia , Camundongos Transgênicos , Vias Neurais/citologia , Vias Neurais/metabolismo , Vias Neurais/fisiologia , Optogenética/métodos , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/metabolismo , Córtex Pré-Frontal/fisiologia , Células Piramidais/metabolismo , Transmissão Sináptica/fisiologia
9.
J Neurosci ; 41(5): 960-971, 2021 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-33402420

RESUMO

Drug-induced neuroadaptations in the mPFC have been implicated in addictive behaviors. Repeated cocaine exposure has been shown to increase pyramidal neuron excitability in the prelimbic (PL) region of the mouse mPFC, an adaptation attributable to a suppression of G protein-gated inwardly rectifying K+ (GIRK) channel activity. After establishing that this neuroadaptation is not seen in adjacent GABA neurons, we used viral GIRK channel ablation and complementary chemogenetic approaches to selectively enhance PL pyramidal neuron excitability in adult mice, to evaluate the impact of this form of plasticity on PL-dependent behaviors. GIRK channel ablation decreased somatodendritic GABAB receptor-dependent signaling and rheobase in PL pyramidal neurons. This manipulation also enhanced the motor-stimulatory effect of cocaine but did not impact baseline activity or trace fear learning. In contrast, selective chemogenetic excitation of PL pyramidal neurons, or chemogenetic inhibition of PL GABA neurons, increased baseline and cocaine-induced activity and disrupted trace fear learning. These effects were mirrored in male mice by selective excitation of PL pyramidal neurons projecting to the VTA, but not NAc or BLA. Collectively, these data show that manipulations enhancing the excitability of PL pyramidal neurons, and specifically those projecting to the VTA, recapitulate behavioral hallmarks of repeated cocaine exposure in mice.SIGNIFICANCE STATEMENT Prolonged exposure to drugs of abuse triggers neuroadaptations that promote core features of addiction. Understanding these neuroadaptations and their implications may suggest interventions capable of preventing or treating addiction. While previous work showed that repeated cocaine exposure increased the excitability of pyramidal neurons in the prelimbic cortex (PL), the behavioral implications of this neuroadaptation remained unclear. Here, we used neuron-specific manipulations to evaluate the impact of increased PL pyramidal neuron excitability on PL-dependent behaviors. Acute or persistent excitation of PL pyramidal neurons potentiated cocaine-induced motor activity and disrupted trace fear conditioning, effects replicated by selective excitation of the PL projection to the VTA. Our work suggests that hyperexcitability of this projection drives key behavioral hallmarks of addiction.


Assuntos
Medo/fisiologia , Aprendizagem/fisiologia , Atividade Motora/fisiologia , Células Piramidais/metabolismo , Área Tegmentar Ventral/metabolismo , Animais , Cocaína/farmacologia , Inibidores da Captação de Dopamina/farmacologia , Medo/efeitos dos fármacos , Medo/psicologia , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Aprendizagem/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Células Piramidais/efeitos dos fármacos , Área Tegmentar Ventral/efeitos dos fármacos
10.
Nature ; 591(7848): 111-116, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33442056

RESUMO

In 1986, electron microscopy was used to reconstruct by hand the entire nervous system of a roundworm, the nematode Caenorhabditis elegans1. Since this landmark study, high-throughput electron-microscopic techniques have enabled reconstructions of much larger mammalian brain circuits at synaptic resolution2,3. Nevertheless, it remains unknown how the structure of a synapse relates to its physiological transmission strength-a key limitation for inferring brain function from neuronal wiring diagrams. Here we combine slice electrophysiology of synaptically connected pyramidal neurons in the mouse somatosensory cortex with correlated light microscopy and high-resolution electron microscopy of all putative synaptic contacts between the recorded neurons. We find a linear relationship between synapse size and strength, providing the missing link in assigning physiological weights to synapses reconstructed from electron microscopy. Quantal analysis also reveals that synapses contain at least 2.7 neurotransmitter-release sites on average. This challenges existing release models and provides further evidence that neocortical synapses operate with multivesicular release4-6, suggesting that they are more complex computational devices than thought, and therefore expanding the computational power of the canonical cortical microcircuitry.


Assuntos
Neocórtex/citologia , Neocórtex/ultraestrutura , Sinapses/fisiologia , Sinapses/ultraestrutura , Transmissão Sináptica , Animais , Tamanho Celular , Fenômenos Eletrofisiológicos , Masculino , Camundongos , Microscopia , Microscopia Eletrônica , Neurotransmissores/metabolismo , Células Piramidais/citologia , Células Piramidais/metabolismo , Células Piramidais/ultraestrutura , Córtex Somatossensorial/citologia , Córtex Somatossensorial/ultraestrutura
11.
Proc Natl Acad Sci U S A ; 118(1)2021 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-33443211

RESUMO

Hippocampal synaptic plasticity is important for learning and memory formation. Homeostatic synaptic plasticity is a specific form of synaptic plasticity that is induced upon prolonged changes in neuronal activity to maintain network homeostasis. While astrocytes are important regulators of synaptic transmission and plasticity, it is largely unclear how they interact with neurons to regulate synaptic plasticity at the circuit level. Here, we show that neuronal activity blockade selectively increases the expression and secretion of IL-33 (interleukin-33) by astrocytes in the hippocampal cornu ammonis 1 (CA1) subregion. This IL-33 stimulates an increase in excitatory synapses and neurotransmission through the activation of neuronal IL-33 receptor complex and synaptic recruitment of the scaffold protein PSD-95. We found that acute administration of tetrodotoxin in hippocampal slices or inhibition of hippocampal CA1 excitatory neurons by optogenetic manipulation increases IL-33 expression in CA1 astrocytes. Furthermore, IL-33 administration in vivo promotes the formation of functional excitatory synapses in hippocampal CA1 neurons, whereas conditional knockout of IL-33 in CA1 astrocytes decreases the number of excitatory synapses therein. Importantly, blockade of IL-33 and its receptor signaling in vivo by intracerebroventricular administration of its decoy receptor inhibits homeostatic synaptic plasticity in CA1 pyramidal neurons and impairs spatial memory formation in mice. These results collectively reveal an important role of astrocytic IL-33 in mediating the negative-feedback signaling mechanism in homeostatic synaptic plasticity, providing insights into how astrocytes maintain hippocampal network homeostasis.


Assuntos
Astrócitos/metabolismo , Região CA1 Hipocampal/metabolismo , Interleucina-33/metabolismo , Plasticidade Neuronal , Transdução de Sinais/efeitos dos fármacos , Memória Espacial/efeitos dos fármacos , Animais , Astrócitos/efeitos dos fármacos , Proteína 4 Homóloga a Disks-Large/metabolismo , Técnicas de Inativação de Genes , Hipocampo/metabolismo , Homeostase , Interleucina-33/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Ratos , Sinapses/efeitos dos fármacos , Sinapses/genética , Sinapses/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Tetrodotoxina/farmacologia
12.
PLoS Comput Biol ; 17(1): e1008573, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33465082

RESUMO

The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. These computational experiments demonstrated that glutamatergic co-stimulation enhances GABA receptor-mediated Cl- influx at low and attenuates or reverses the Cl- efflux at high initial [Cl-]i. The size of glutamatergic influence on GABAergic Cl--fluxes depends on the conductance, decay kinetics, and localization of glutamatergic inputs. Surprisingly, the glutamatergic shift in GABAergic Cl--fluxes is invariant to latencies between GABAergic and glutamatergic inputs over a substantial interval. In agreement with experimental data, simulations in a reconstructed CA3 pyramidal neuron with physiological patterns of correlated activity revealed that coincident glutamatergic synaptic inputs contribute significantly to the activity-dependent [Cl-]i changes. Whereas the influence of spatial correlation between distributed glutamatergic and GABAergic inputs was negligible, their temporal correlation played a significant role. In summary, our results demonstrate that glutamatergic co-stimulation had a substantial impact on ionic plasticity of GABAergic responses, enhancing the attenuation of GABAergic inhibition in the mature nervous systems, but suppressing GABAergic [Cl-]i changes in the immature brain. Therefore, glutamatergic shift in GABAergic Cl--fluxes should be considered as a relevant factor of short-term plasticity.


Assuntos
Cloretos/metabolismo , Células Piramidais/metabolismo , Receptores de GABA-A/metabolismo , Sinapses/metabolismo , Animais , Região CA3 Hipocampal/citologia , Biologia Computacional , Bases de Dados Factuais , Modelos Neurológicos , Plasticidade Neuronal/fisiologia , Transmissão Sináptica , Ácido gama-Aminobutírico/metabolismo
13.
Nat Commun ; 12(1): 297, 2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33436612

RESUMO

GABAA receptors (GABAARs) are the primary fast inhibitory ion channels in the central nervous system. Dysfunction of trafficking and localization of GABAARs to cell membranes is clinically associated with severe psychiatric disorders in humans. The GABARAP protein is known to support the stability of GABAARs in synapses, but the underlying molecular mechanisms remain to be elucidated. Here, we show that GABARAP/GABARAPL1 directly binds to a previously unappreciated region in the γ2 subunit of GABAAR. We demonstrate that GABARAP functions to stabilize GABAARs via promoting its trafficking pathway instead of blocking receptor endocytosis. The GABARAPL1-γ2-GABAAR crystal structure reveals the mechanisms underlying the complex formation. We provide evidence showing that phosphorylation of γ2-GABAAR differentially modulate the receptor's binding to GABARAP and the clathrin adaptor protein AP2. Finally, we demonstrate that GABAergic synaptic currents are reduced upon specific blockage of the GABARAP-GABAAR complex formation. Collectively, our results reveal that GABARAP/GABARAPL1, but not other members of the Atg8 family proteins, specifically regulates synaptic localization of GABAARs via modulating the trafficking of the receptor.


Assuntos
Proteínas Reguladoras de Apoptose/química , Proteínas Reguladoras de Apoptose/metabolismo , Neurônios GABAérgicos/metabolismo , Proteínas Associadas aos Microtúbulos/química , Proteínas Associadas aos Microtúbulos/metabolismo , Receptores de GABA-A/metabolismo , Transmissão Sináptica , Complexo 2 de Proteínas Adaptadoras/química , Complexo 2 de Proteínas Adaptadoras/metabolismo , Motivos de Aminoácidos , Animais , Família da Proteína 8 Relacionada à Autofagia , Células HEK293 , Humanos , Masculino , Camundongos Endogâmicos C57BL , Modelos Moleculares , Fosforilação , Ligação Proteica , Estrutura Secundária de Proteína , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Transporte Proteico , Células Piramidais/metabolismo , Ratos , Receptores de GABA-A/química , Relação Estrutura-Atividade
14.
Proc Natl Acad Sci U S A ; 118(5)2021 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-33495318

RESUMO

Clinical studies have reported that the psychedelic lysergic acid diethylamide (LSD) enhances empathy and social behavior (SB) in humans, but its mechanism of action remains elusive. Using a multidisciplinary approach including in vivo electrophysiology, optogenetics, behavioral paradigms, and molecular biology, the effects of LSD on SB and glutamatergic neurotransmission in the medial prefrontal cortex (mPFC) were studied in male mice. Acute LSD (30 µg/kg) injection failed to increase SB. However, repeated LSD (30 µg/kg, once a day, for 7 days) administration promotes SB, without eliciting antidepressant/anxiolytic-like effects. Optogenetic inhibition of mPFC excitatory neurons dramatically inhibits social interaction and nullifies the prosocial effect of LSD. LSD potentiates the α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and 5-HT2A, but not N-methyl-D-aspartate (NMDA) and 5-HT1A, synaptic responses in the mPFC and increases the phosphorylation of the serine-threonine protein kinases Akt and mTOR. In conditional knockout mice lacking Raptor (one of the structural components of the mTORC1 complex) in excitatory glutamatergic neurons (Raptor f/f :Camk2alpha-Cre), the prosocial effects of LSD and the potentiation of 5-HT2A/AMPA synaptic responses were nullified, demonstrating that LSD requires the integrity of mTORC1 in excitatory neurons to promote SB. Conversely, in knockout mice lacking Raptor in GABAergic neurons of the mPFC (Raptor f/f :Gad2-Cre), LSD promotes SB. These results indicate that LSD selectively enhances SB by potentiating mPFC excitatory transmission through 5-HT2A/AMPA receptors and mTOR signaling. The activation of 5-HT2A/AMPA/mTORC1 in the mPFC by psychedelic drugs should be explored for the treatment of mental diseases with SB impairments such as autism spectrum disorder and social anxiety disorder.


Assuntos
Comportamento Animal/efeitos dos fármacos , Dietilamida do Ácido Lisérgico/farmacologia , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Comportamento Social , Transmissão Sináptica/efeitos dos fármacos , Animais , Aprendizagem da Esquiva/efeitos dos fármacos , Masculino , Camundongos Endogâmicos C57BL , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Optogenética , Fosforilação/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Receptores de AMPA/agonistas , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/agonistas , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores de Serotonina/metabolismo , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Serina-Treonina Quinases TOR/metabolismo
15.
eNeuro ; 8(1)2021.
Artigo em Inglês | MEDLINE | ID: mdl-33495243

RESUMO

The regulation of neuronal soma size is essential for appropriate brain circuit function and its dysregulation is associated with several neurodevelopmental disorders. A defect in the dendritic growth and elaboration of motor neocortical pyramidal neurons in neonates lacking neuregulin-4 (NRG4) has previously been reported. In this study, we investigated whether the loss of NRG4 causes further morphologic defects that are specific to these neurons. We analyzed the soma size of pyramidal neurons of layer (L)2/3 and L5 of the motor cortex and a subpopulation of multipolar interneurons in this neocortical region in Nrg4 +/+ and Nrg4 -/- mice. There were significant decreases in pyramidal neuron soma size in Nrg4 -/- mice compared with Nrg4 +/+ littermates at all stages studied [postnatal day (P)10, P30, and P60]. The reduction was especially marked at P10 and in L5 pyramidal neurons. Soma size was not significantly different for multipolar interneurons at any age. This in vivo phenotype was replicated in pyramidal neurons cultured from Nrg4 -/- mice and was rescued by NRG treatment. Analysis of a public single-cell RNA sequencing repository revealed discrete Nrg4 and Erbb4 expression in subpopulations of L5 pyramidal neurons, suggesting that the observed defects were due in part to loss of autocrine Nrg4/ErbB4 signaling. The pyramidal phenotype in the motor cortex of Nrg4 -/- mice was associated with a lack of Rotarod test improvement in P60 mice, suggesting that absence of NRG4 causes alterations in motor performance.


Assuntos
Córtex Motor , Animais , Camundongos , Córtex Motor/metabolismo , Neuregulina-1/genética , Neurregulinas/metabolismo , Neurônios/metabolismo , Células Piramidais/metabolismo
16.
Proc Natl Acad Sci U S A ; 118(2)2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33372130

RESUMO

How do firing patterns in a cortical circuit change when inhibitory neurons are excited? We virally expressed an excitatory designer receptor exclusively activated by a designer drug (Gq-DREADD) in all inhibitory interneuron types of the CA1 region of the hippocampus in the rat. While clozapine N-oxide (CNO) activation of interneurons suppressed firing of pyramidal cells, unexpectedly the majority of interneurons also decreased their activity. CNO-induced inhibition decreased over repeated sessions, which we attribute to long-term synaptic plasticity between interneurons and pyramidal cells. Individual interneurons did not display sustained firing but instead transiently enhanced their activity, interleaved with suppression of others. The power of the local fields in the theta band was unaffected, while power at higher frequencies was attenuated, likely reflecting reduced pyramidal neuron spiking. The incidence of sharp wave ripples decreased but the surviving ripples were associated with stronger population firing compared with the control condition. These findings demonstrate that DREADD activation of interneurons brings about both short-term and long-term circuit reorganization, which should be taken into account in the interpretation of chemogenic effects on behavior.


Assuntos
Região CA1 Hipocampal/metabolismo , Interneurônios/fisiologia , Células Piramidais/metabolismo , Animais , Região CA1 Hipocampal/efeitos dos fármacos , Clozapina/análogos & derivados , Clozapina/farmacologia , Feminino , Hipocampo/metabolismo , Interneurônios/efeitos dos fármacos , Interneurônios/metabolismo , Masculino , Inibição Neural/fisiologia , Plasticidade Neuronal/fisiologia , Parvalbuminas/metabolismo , Ratos , Ratos Sprague-Dawley , Transmissão Sináptica/fisiologia
17.
Nature ; 590(7845): 315-319, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33328636

RESUMO

Effective pharmacotherapy for major depressive disorder remains a major challenge, as more than 30% of patients are resistant to the first line of treatment (selective serotonin reuptake inhibitors)1. Sub-anaesthetic doses of ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist2,3, provide rapid and long-lasting antidepressant effects in these patients4-6, but the molecular mechanism of these effects remains unclear7,8. Ketamine has been proposed to exert its antidepressant effects through its metabolite (2R,6R)-hydroxynorketamine ((2R,6R)-HNK)9. The antidepressant effects of ketamine and (2R,6R)-HNK in rodents require activation of the mTORC1 kinase10,11. mTORC1 controls various neuronal functions12, particularly through cap-dependent initiation of mRNA translation via the phosphorylation and inactivation of eukaryotic initiation factor 4E-binding proteins (4E-BPs)13. Here we show that 4E-BP1 and 4E-BP2 are key effectors of the antidepressant activity of ketamine and (2R,6R)-HNK, and that ketamine-induced hippocampal synaptic plasticity depends on 4E-BP2 and, to a lesser extent, 4E-BP1. It has been hypothesized that ketamine activates mTORC1-4E-BP signalling in pyramidal excitatory cells of the cortex8,14. To test this hypothesis, we studied the behavioural response to ketamine and (2R,6R)-HNK in mice lacking 4E-BPs in either excitatory or inhibitory neurons. The antidepressant activity of the drugs is mediated by 4E-BP2 in excitatory neurons, and 4E-BP1 and 4E-BP2 in inhibitory neurons. Notably, genetic deletion of 4E-BP2 in inhibitory neurons induced a reduction in baseline immobility in the forced swim test, mimicking an antidepressant effect. Deletion of 4E-BP2 specifically in inhibitory neurons also prevented the ketamine-induced increase in hippocampal excitatory neurotransmission, and this effect concurred with the inability of ketamine to induce a long-lasting decrease in inhibitory neurotransmission. Overall, our data show that 4E-BPs are central to the antidepressant activity of ketamine.


Assuntos
Antidepressivos/farmacologia , Fator de Iniciação 4E em Eucariotos/metabolismo , Ketamina/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Transtorno Depressivo Maior/tratamento farmacológico , Fatores de Iniciação em Eucariotos/genética , Fatores de Iniciação em Eucariotos/metabolismo , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Interneurônios/metabolismo , Ketamina/análogos & derivados , Ketamina/metabolismo , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Camundongos , Mutação , Inibição Neural/efeitos dos fármacos , Inibição Neural/genética , Neurônios/classificação , Neurônios/citologia , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Transmissão Sináptica/efeitos dos fármacos
18.
Nature ; 590(7844): 111-114, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33328635

RESUMO

Single neocortical neurons are driven by populations of excitatory inputs, which form the basis of neuronal selectivity to features of sensory input. Excitatory connections are thought to mature during development through activity-dependent Hebbian plasticity1, whereby similarity between presynaptic and postsynaptic activity selectively strengthens some synapses and weakens others2. Evidence in support of this process includes measurements of synaptic ultrastructure and in vitro and in vivo physiology and imaging studies3-8. These corroborating lines of evidence lead to the prediction that a small number of strong synaptic inputs drive neuronal selectivity, whereas weak synaptic inputs are less correlated with the somatic output and modulate activity overall6,7. Supporting evidence from cortical circuits, however, has been limited to measurements of neighbouring, connected cell pairs, raising the question of whether this prediction holds for a broad range of synapses converging onto cortical neurons. Here we measure the strengths of functionally characterized excitatory inputs contacting single pyramidal neurons in ferret primary visual cortex (V1) by combining in vivo two-photon synaptic imaging and post hoc electron microscopy. Using electron microscopy reconstruction of individual synapses as a metric of strength, we find no evidence that strong synapses have a predominant role in the selectivity of cortical neuron responses to visual stimuli. Instead, selectivity appears to arise from the total number of synapses activated by different stimuli. Moreover, spatial clustering of co-active inputs appears to be reserved for weaker synapses, enhancing the contribution of weak synapses to somatic responses. Our results challenge the role of Hebbian mechanisms in shaping neuronal selectivity in cortical circuits, and suggest that selectivity reflects the co-activation of large populations of presynaptic neurons with similar properties and a mixture of strengths.


Assuntos
Vias Neurais , Células Piramidais/metabolismo , Sinapses/metabolismo , Córtex Visual/citologia , Córtex Visual/fisiologia , Animais , Feminino , Furões , Microscopia Eletrônica de Varredura , Modelos Neurológicos , Estimulação Luminosa , Células Piramidais/ultraestrutura , Sinapses/ultraestrutura
19.
Neuron ; 109(4): 663-676.e5, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33333001

RESUMO

Neocortical pyramidal neurons regulate firing around a stable mean firing rate (FR) that can differ by orders of magnitude between neurons, but the factors that determine where individual neurons sit within this broad FR distribution are not understood. To access low- and high-FR neurons for ex vivo analysis, we used Ca2+- and UV-dependent photoconversion of CaMPARI2 in vivo to permanently label neurons according to mean FR. CaMPARI2 photoconversion was correlated with immediate early gene expression and higher FRs ex vivo and tracked the drop and rebound in ensemble mean FR induced by prolonged monocular deprivation. High-activity L4 pyramidal neurons had greater intrinsic excitability and recurrent excitatory synaptic strength, while E/I ratio, local output strength, and local connection probability were not different. Thus, in L4 pyramidal neurons (considered a single transcriptional cell type), a broad mean FR distribution is achieved through graded differences in both intrinsic and synaptic properties.


Assuntos
Cálcio/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciais Pós-Sinápticos Inibidores/fisiologia , Neurônios/metabolismo , Células Piramidais/metabolismo , Transmissão Sináptica/fisiologia , Animais , Cálcio/análise , Potenciais Pós-Sinápticos Excitadores/efeitos da radiação , Feminino , Potenciais Pós-Sinápticos Inibidores/efeitos da radiação , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/química , Neurônios/efeitos da radiação , Células Piramidais/química , Células Piramidais/efeitos da radiação , Transmissão Sináptica/efeitos da radiação , Raios Ultravioleta
20.
Int J Mol Sci ; 22(1)2020 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-33375653

RESUMO

Angiotensin converting enzyme 2 (ACE2) is a critical component of the compensatory axis of the renin angiotensin system. Alterations in ACE2 gene and protein expression, and activity mediated by A Disintegrin And Metalloprotease 17 (ADAM17), a member of the "A Disintegrin And Metalloprotease" (ADAM) family are implicated in several cardiovascular and neurodegenerative diseases. We previously reported that activation of kinin B1 receptor (B1R) in the brain increases neuroinflammation, oxidative stress and sympathoexcitation, leading to the development of neurogenic hypertension. We also showed evidence for ADAM17-mediated ACE2 shedding in neurons. However, whether kinin B1 receptor (B1R) activation has any role in altering ADAM17 activity and its effect on ACE2 shedding in neurons is not known. In this study, we tested the hypothesis that activation of B1R upregulates ADAM17 and results in ACE2 shedding in neurons. To test this hypothesis, we stimulated wild-type and B1R gene-deleted mouse neonatal primary hypothalamic neuronal cultures with a B1R-specific agonist and measured the activities of ADAM17 and ACE2 in neurons. B1R stimulation significantly increased ADAM17 activity and decreased ACE2 activity in wild-type neurons, while pretreatment with a B1R-specific antagonist, R715, reversed these changes. Stimulation with specific B1R agonist Lys-Des-Arg9-Bradykinin (LDABK) did not show any effect on ADAM17 or ACE2 activities in neurons with B1R gene deletion. These data suggest that B1R activation results in ADAM17-mediated ACE2 shedding in primary hypothalamic neurons. In addition, stimulation with high concentration of glutamate significantly increased B1R gene and protein expression, along with increased ADAM17 and decreased ACE2 activities in wild-type neurons. Pretreatment with B1R-specific antagonist R715 reversed these glutamate-induced effects suggesting that indeed B1R is involved in glutamate-mediated upregulation of ADAM17 activity and ACE2 shedding.


Assuntos
Proteína ADAM17/metabolismo , Enzima de Conversão de Angiotensina 2/metabolismo , Neurônios/metabolismo , Animais , Células Cultivadas , Regulação da Expressão Gênica/efeitos dos fármacos , Ácido Glutâmico/metabolismo , Ácido Glutâmico/farmacologia , Hipotálamo/metabolismo , Camundongos , Camundongos Knockout , Modelos Biológicos , Células Piramidais/metabolismo
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