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1.
Neuron ; 109(8): 1365-1380.e5, 2021 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-33740416

RESUMO

Sex differences in pain severity, response, and pathological susceptibility are widely reported, but the neural mechanisms that contribute to these outcomes remain poorly understood. Here we show that dopamine (DA) neurons in the ventrolateral periaqueductal gray/dorsal raphe (vlPAG/DR) differentially regulate pain-related behaviors in male and female mice through projections to the bed nucleus of the stria terminalis (BNST). We find that activation of vlPAG/DRDA+ neurons or vlPAG/DRDA+ terminals in the BNST reduces nociceptive sensitivity during naive and inflammatory pain states in male mice, whereas activation of this pathway in female mice leads to increased locomotion in the presence of salient stimuli. We additionally use slice physiology and genetic editing approaches to demonstrate that vlPAG/DRDA+ projections to the BNST drive sex-specific responses to pain through DA signaling, providing evidence of a novel ascending circuit for pain relief in males and contextual locomotor response in females.


Assuntos
Neurônios Dopaminérgicos/fisiologia , Núcleo Dorsal da Rafe/fisiologia , Atividade Motora/fisiologia , Dor/fisiopatologia , Substância Cinzenta Periaquedutal/fisiologia , Caracteres Sexuais , Animais , Comportamento Animal/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Masculino , Camundongos , Camundongos Transgênicos , Medição da Dor
2.
Nat Commun ; 12(1): 413, 2021 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-33462202

RESUMO

Long-term potentiation (LTP) at hippocampal CA1 synapses can be expressed by an increase either in the number (N) of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors or in their single channel conductance (γ). Here, we have established how these distinct synaptic processes contribute to the expression of LTP in hippocampal slices obtained from young adult rodents. LTP induced by compressed theta burst stimulation (TBS), with a 10 s inter-episode interval, involves purely an increase in N (LTPN). In contrast, either a spaced TBS, with a 10 min inter-episode interval, or a single TBS, delivered when PKA is activated, results in LTP that is associated with a transient increase in γ (LTPγ), caused by the insertion of calcium-permeable (CP)-AMPA receptors. Activation of CaMKII is necessary and sufficient for LTPN whilst PKA is additionally required for LTPγ. Thus, two mechanistically distinct forms of LTP co-exist at these synapses.


Assuntos
Região CA1 Hipocampal/fisiologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciação de Longa Duração/fisiologia , Receptores de AMPA/metabolismo , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Masculino , Memória de Longo Prazo/fisiologia , Técnicas de Patch-Clamp , Ratos , Ritmo Teta/fisiologia
3.
J Neurosci ; 41(7): 1489-1504, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33397711

RESUMO

Intrinsically photosensitive retinal ganglion cells (ipRGCs) exhibit melanopsin-dependent light responses that persist in the absence of rod and cone photoreceptor-mediated input. In addition to signaling anterogradely to the brain, ipRGCs signal retrogradely to intraretinal circuitry via gap junction-mediated electrical synapses with amacrine cells (ACs). However, the targets and functions of these intraretinal signals remain largely unknown. Here, in mice of both sexes, we identify circuitry that enables M5 ipRGCs to locally inhibit retinal neurons via electrical synapses with a nonspiking GABAergic AC. During pharmacological blockade of rod- and cone-mediated input, whole-cell recordings of corticotropin-releasing hormone-expressing (CRH+) ACs reveal persistent visual responses that require both melanopsin expression and gap junctions. In the developing retina, ipRGC-mediated input to CRH+ ACs is weak or absent before eye opening, indicating a primary role for this input in the mature retina (i.e., in parallel with rod- and cone-mediated input). Among several ipRGC types, only M5 ipRGCs exhibit consistent anatomical and physiological coupling to CRH+ ACs. Optogenetic stimulation of local CRH+ ACs directly drives IPSCs in M4 and M5, but not M1-M3, ipRGCs. CRH+ ACs also inhibit M2 ipRGC-coupled spiking ACs, demonstrating direct interaction between discrete networks of ipRGC-coupled interneurons. Together, these results demonstrate a functional role for electrical synapses in translating ipRGC activity into feedforward and feedback inhibition of local retinal circuits.SIGNIFICANCE STATEMENT Melanopsin directly generates light responses in intrinsically photosensitive retinal ganglion cells (ipRGCs). Through gap junction-mediated electrical synapses with retinal interneurons, these uniquely photoreceptive RGCs may also influence the activity and output of neuronal circuits within the retina. Here, we identified and studied an electrical synaptic circuit that, in principle, could couple ipRGC activity to the chemical output of an identified retinal interneuron. Specifically, we found that M5 ipRGCs form electrical synapses with corticotropin-releasing hormone-expressing amacrine cells, which locally release GABA to inhibit specific RGC types. Thus, ipRGCs are poised to influence the output of diverse retinal circuits via electrical synapses with interneurons.


Assuntos
Inibição Neural/fisiologia , Células Fotorreceptoras de Vertebrados/fisiologia , Retina/fisiologia , Células Ganglionares da Retina/fisiologia , Células Amácrinas/fisiologia , Animais , Hormônio Liberador da Corticotropina/fisiologia , Fenômenos Eletrofisiológicos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Junções Comunicantes/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Optogenética , Células Fotorreceptoras de Vertebrados/efeitos dos fármacos , Células Fotorreceptoras Retinianas Cones/efeitos dos fármacos , Células Fotorreceptoras Retinianas Bastonetes/efeitos dos fármacos , Opsinas de Bastonetes/metabolismo , Sinapses/fisiologia , Ácido gama-Aminobutírico/fisiologia
4.
J Neurosci ; 41(7): 1401-1417, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33402422

RESUMO

Throughout the nervous system, the convergence of two or more presynaptic inputs on a target cell is commonly observed. The question we ask here is to what extent converging inputs influence each other's structural and functional synaptic plasticity. In complex circuits, isolating individual inputs is difficult because postsynaptic cells can receive thousands of inputs. An ideal model to address this question is the Drosophila larval neuromuscular junction (NMJ) where each postsynaptic muscle cell receives inputs from two glutamatergic types of motor neurons (MNs), known as 1b and 1s MNs. Notably, each muscle is unique and receives input from a different combination of 1b and 1s MNs; we surveyed multiple muscles for this reason. Here, we identified a cell-specific promoter that allows ablation of 1s MNs postinnervation and measured structural and functional responses of convergent 1b NMJs using microscopy and electrophysiology. For all muscles examined in both sexes, ablation of 1s MNs resulted in NMJ expansion and increased spontaneous neurotransmitter release at corresponding 1b NMJs. This demonstrates that 1b NMJs can compensate for the loss of convergent 1s MNs. However, only a subset of 1b NMJs showed compensatory evoked neurotransmission, suggesting target-specific plasticity. Silencing 1s MNs led to similar plasticity at 1b NMJs, suggesting that evoked neurotransmission from 1s MNs contributes to 1b synaptic plasticity. Finally, we genetically blocked 1s innervation in male larvae and robust 1b synaptic plasticity was eliminated, raising the possibility that 1s NMJ formation is required to set up a reference for subsequent synaptic perturbations.SIGNIFICANCE STATEMENT In complex neural circuits, multiple convergent inputs contribute to the activity of the target cell, but whether synaptic plasticity exists among these inputs has not been thoroughly explored. In this study, we examined synaptic plasticity in the structurally and functionally tractable Drosophila larval neuromuscular system. In this convergent circuit, each muscle is innervated by a unique pair of motor neurons. Removal of one neuron after innervation causes the adjacent neuron to increase neuromuscular junction outgrowth and functional output. However, this is not a general feature as each motor neuron differentially compensates. Further, robust compensation requires initial coinnervation by both neurons. Understanding how neurons respond to perturbations in adjacent neurons will provide insight into nervous system plasticity in both healthy and disease states.


Assuntos
Drosophila melanogaster/fisiologia , Junção Neuromuscular/fisiologia , Plasticidade Neuronal/fisiologia , Sinapses/fisiologia , Animais , Fenômenos Eletrofisiológicos , Potenciais Pós-Sinápticos Excitadores/genética , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Técnicas de Inativação de Genes , Larva , Masculino , Neurônios Motores/metabolismo , Músculos/inervação , Músculos/fisiologia , Junção Neuromuscular/genética , Plasticidade Neuronal/genética , Receptores de Glutamato/metabolismo , Transmissão Sináptica
5.
Neurosci Lett ; 745: 135647, 2021 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-33444673

RESUMO

Experimental studies have indicated that prolonged ketamine exposure in neonates at anesthetic doses causes neuronal apoptosis, which contributes to long-term impairments of learning and memory later in life. The neuronal excitotoxicity mediated by compensatory upregulation of N-methyl-d-aspartate receptors (NMDARs) is proposed to be the underlying mechanism. However, this view does not convincingly explain why excitotoxicity-related apoptotic injury develops selectively in immature neurons. We proposed that the GABAA receptors (GABAARs)-mediated excitatory synaptic signaling due to high expression of the Na+-K+-2Cl- co-transporter (NKCC1), occurring during the early neuronal development period, plays a distinct role in the susceptibility of immature neurons to ketamine-induced injury. Using whole-cell patch-clamp recordings from the forebrain slices containing the anterior cingulate cortex, we found that in vivo repeated ketamine administration significantly induced neuronal hyperexcitability in neonatal, but not adolescent, rats. Such hyperexcitability was accompanied by the increase both in GABAAR- and NMDAR-mediated synaptic transmissions. An interference with the NKCC1 by bumetanide treatment completely reversed these enhanced effects of ketamine exposure and blocked GABAAR-mediated postsynaptic current activity. Thus, these findings were significant as they showed, for the first time, that GABAAR-mediated excitatory action may contribute distinctly to neuronal excitotoxic effects of ketamine on immature neurons in the developing brain.


Assuntos
Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Neurônios GABAérgicos/efeitos dos fármacos , Giro do Cíngulo/efeitos dos fármacos , Giro do Cíngulo/crescimento & desenvolvimento , Ketamina/administração & dosagem , Sinapses/efeitos dos fármacos , Analgésicos/administração & dosagem , Animais , Animais Recém-Nascidos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Neurônios GABAérgicos/fisiologia , Masculino , Ratos , Ratos Sprague-Dawley , Sinapses/fisiologia
6.
Epilepsia ; 62(2): 517-528, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33400301

RESUMO

OBJECTIVE: Mutations of the cyclin-dependent kinase-like 5 (CDKL5) gene cause severe neurodevelopmental disorders characterized by intractable epilepsy, intellectual disability, and autism. Multiple mouse models generated for mechanistic studies have exhibited phenotypes similar to some human pathological features, but none of the models has developed one of the major symptoms affecting CDKL5 deficiency disorder (CDD) patients: intractable recurrent seizures. As disrupted neuronal excitation/inhibition balance is closely associated with the activity of glutamatergic and γ-aminobutyric acidergic (GABAergic) neurons, our aim was to study the effect of the loss of CDKL5 in different types of neurons on epilepsy. METHODS: Using the Cre-LoxP system, we generated conditional knockout (cKO) mouse lines allowing CDKL5 deficiency in glutamatergic or GABAergic neurons. We employed noninvasive video recording and in vivo electrophysiological approaches to study seizure activity in these Cdkl5 cKO mice. Furthermore, we conducted Timm staining to confirm a morphological alteration, mossy fiber sprouting, which occurs with limbic epilepsy in both human and mouse brains. Finally, we performed whole-cell patch clamp in dentate granule cells to investigate cell-intrinsic properties and synaptic excitatory activity. RESULTS: We demonstrate that Emx1- or CamK2α-derived Cdkl5 cKO mice manifest high-frequency spontaneous seizure activities recapitulating the epilepsy of CDD patients, which ultimately led to sudden death in mice. However, Cdkl5 deficiency in GABAergic neurons does not generate such seizures. The seizures were accompanied by typical epileptic features including higher amplitude spikes for epileptiform discharges and abnormal hippocampal mossy fiber sprouting. We also found an increase in spontaneous and miniature excitatory postsynaptic current frequencies but no change in amplitudes in the dentate granule cells of Emx1-cKO mice, indicating enhanced excitatory synaptic activity. SIGNIFICANCE: Our study demonstrates that Cdkl5 cKO mice, serving as an animal model to study recurrent spontaneous seizures, have potential value for the pathological study of CDD-related seizures and for therapeutic innovation.


Assuntos
Síndromes Epilépticas/genética , Neurônios GABAérgicos/metabolismo , Ácido Glutâmico/metabolismo , Proteínas Serina-Treonina Quinases/genética , Convulsões/genética , Espasmos Infantis/genética , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Giro Denteado/citologia , Giro Denteado/metabolismo , Modelos Animais de Doenças , Eletroencefalografia , Síndromes Epilépticas/metabolismo , Síndromes Epilépticas/fisiopatologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Neurônios GABAérgicos/patologia , Proteínas de Homeodomínio , Camundongos , Camundongos Knockout , Fibras Musgosas Hipocampais/patologia , Neurônios/metabolismo , Neurônios/patologia , Técnicas de Patch-Clamp , Prosencéfalo , Convulsões/metabolismo , Convulsões/fisiopatologia , Espasmos Infantis/metabolismo , Espasmos Infantis/fisiopatologia , Fatores de Transcrição
7.
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
8.
J Neurosci ; 41(6): 1251-1264, 2021 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-33443089

RESUMO

Neural competition plays an essential role in active selection processes of noisy and ambiguous input signals, and it is assumed to underlie emergent properties of brain functioning, such as perceptual organization and decision-making. Despite ample theoretical research on neural competition, experimental tools to allow neurophysiological investigation of competing neurons have not been available. We developed a "hybrid" system where real-life neurons and a computer-simulated neural circuit interacted. It enabled us to construct a mutual inhibition circuit between two real-life pyramidal neurons. We then asked what dynamics this minimal unit of neural competition exhibits and compared them with the known behavioral-level dynamics of neural competition. We found that the pair of neurons shows bistability when activated simultaneously by current injections. The addition of modeled synaptic noise and changes in the activation strength showed that the dynamics of the circuit are strikingly similar to the known properties of bistable visual perception: The distribution of dominance durations showed a right-skewed shape, and the changes of the activation strengths caused changes in dominance, dominance durations, and reversal rates as stated in the well-known empirical laws of bistable perception known as Levelt's propositions.SIGNIFICANCE STATEMENT Visual perception emerges as the result of neural systems actively organizing visual signals that involves selection processes of competing neurons. While the neural competition, realized by a "mutual inhibition" circuit has been examined in many theoretical studies, its properties have not been investigated in real neurons. We have developed a "hybrid" system where two real-life pyramidal neurons in a mouse brain slice interact through a computer-simulated mutual inhibition circuit. We found that simultaneous activation of the neurons leads to bistable activity. We investigated the effect of noise and the effect of changes in the activation strength on the dynamics. We observed that the pair of neurons exhibit dynamics strikingly similar to the known properties of bistable visual perception.


Assuntos
Rede Nervosa/fisiologia , Inibição Neural/fisiologia , Estimulação Luminosa/métodos , Células Piramidais/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Rede Nervosa/citologia , Técnicas de Cultura de Órgãos , Córtex Visual/citologia
9.
Nat Commun ; 12(1): 100, 2021 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-33397954

RESUMO

Hippocampal synaptic plasticity includes both long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength, and has been implicated in shaping place field representations that form upon initial exposure to a novel environment. However, direct evidence causally linking either LTP or LTD to place fields remains limited. Here, we show that hippocampal LTD regulates the acute formation and maintenance of place fields using electrophysiology and blocking specifically LTD in freely-moving rats. We also show that exploration of a novel environment produces a widespread and pathway specific de novo synaptic depression in the dorsal hippocampus. Furthermore, disruption of this pathway-specific synaptic depression alters both the dynamics of place field formation and the stability of the newly formed place fields, affecting spatial memory in rats. These results suggest that activity-dependent synaptic depression is required for the acquisition and maintenance of novel spatial information.


Assuntos
Região CA1 Hipocampal/fisiologia , Depressão Sináptica de Longo Prazo/fisiologia , Potenciais de Ação/fisiologia , Animais , Aprendizagem da Esquiva , Endocitose , Potenciais Pós-Sinápticos Excitadores/fisiologia , Comportamento Exploratório , Peptídeos/metabolismo , Ratos Sprague-Dawley , Receptores de AMPA/metabolismo
10.
J Neurosci ; 41(7): 1443-1454, 2021 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-33334866

RESUMO

Renshaw cells mediate recurrent inhibition between motoneurons within the spinal cord. The function of this circuit is not clear; we previously suggested based on computational modeling that it may cancel oscillations in muscle activity around 10 Hz, thereby reducing physiological tremor. Such tremor is especially problematic for dexterous hand movements, yet knowledge of recurrent inhibitory function is sparse for the control of the primate upper limb, where no direct measurements have been made to date. In this study, we made intracellular penetrations into 89 motoneurons in the cervical enlargement of four terminally anesthetized female macaque monkeys, and recorded recurrent IPSPs in response to antidromic stimulation of motor axons. Recurrent inhibition was strongest to motoneurons innervating shoulder muscles and elbow extensors, weak to wrist and digit extensors, and almost absent to the intrinsic muscles of the hand. Recurrent inhibitory connections often spanned joints, for example from motoneurons innervating wrist and digit muscles to those controlling the shoulder and elbow. Wrist and digit flexor motoneurons sometimes inhibited the corresponding extensors, and vice versa. This complex connectivity presumably reflects the flexible usage of the primate upper limb. Using trains of stimuli to motor nerves timed as a Poisson process and coherence analysis, we also examined the temporal properties of recurrent inhibition. The recurrent feedback loop effectively carried frequencies up to 100 Hz, with a coherence peak around 20 Hz. The coherence phase validated predictions from our previous computational model, supporting the idea that recurrent inhibition may function to reduce tremor.SIGNIFICANCE STATEMENT We present the first direct measurements of recurrent inhibition in primate upper limb motoneurons, revealing that it is more flexibly organized than previous observations in cat. Recurrent inhibitory connections were relatively common between motoneurons controlling muscles that act at different joints, and between flexors and extensors. As in the cat, connections were minimal for motoneurons innervating the most distal intrinsic hand muscles. Empirical data are consistent with previous modeling: temporal properties of the recurrent inhibitory feedback loop are compatible with a role in reducing physiological tremor by suppressing oscillations around 10 Hz.


Assuntos
Inibição Neural/fisiologia , Extremidade Superior/fisiologia , Animais , Axônios/fisiologia , Estimulação Elétrica , Potenciais Pós-Sinápticos Excitadores/fisiologia , Retroalimentação Fisiológica , Feminino , Macaca mulatta , Neurônios Motores/fisiologia , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Neurônios/fisiologia , Células de Renshaw/fisiologia , Medula Espinal/citologia , Medula Espinal/fisiologia , Extremidade Superior/inervação
11.
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
12.
Proc Natl Acad Sci U S A ; 118(2)2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33372133

RESUMO

Glutamate uptake into synaptic vesicles (SVs) depends on cation/H+ exchange activity, which converts the chemical gradient (ΔpH) into membrane potential (Δψ) across the SV membrane at the presynaptic terminals. Thus, the proper recruitment of cation/H+ exchanger to SVs is important in determining glutamate quantal size, yet little is known about its localization mechanism. Here, we found that secretory carrier membrane protein 5 (SCAMP5) interacted with the cation/H+ exchanger NHE6, and this interaction regulated NHE6 recruitment to glutamatergic presynaptic terminals. Protein-protein interaction analysis with truncated constructs revealed that the 2/3 loop domain of SCAMP5 is directly associated with the C-terminal region of NHE6. The use of optical imaging and electrophysiological recording showed that small hairpin RNA-mediated knockdown (KD) of SCAMP5 or perturbation of SCAMP5/NHE6 interaction markedly inhibited axonal trafficking and the presynaptic localization of NHE6, leading to hyperacidification of SVs and a reduction in the quantal size of glutamate release. Knockout of NHE6 occluded the effect of SCAMP5 KD without causing additional defects. Together, our results reveal that as a key regulator of axonal trafficking and synaptic localization of NHE6, SCAMP5 could adjust presynaptic strength by regulating quantal size at glutamatergic synapses. Since both proteins are autism candidate genes, the reduced quantal size by interrupting their interaction may underscore synaptic dysfunction observed in autism.


Assuntos
Ácido Glutâmico/metabolismo , Proteínas de Membrana/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Axônios/metabolismo , Transporte Biológico , Linhagem Celular , Potenciais Pós-Sinápticos Excitadores/fisiologia , Células HEK293 , Humanos , Proteínas de Membrana/fisiologia , Técnicas de Patch-Clamp , Terminações Pré-Sinápticas/fisiologia , Transporte Proteico , Trocadores de Sódio-Hidrogênio/fisiologia , Sinapses/metabolismo , Transmissão Sináptica/fisiologia , Vesículas Sinápticas/metabolismo
13.
J Neurosci ; 41(6): 1207-1217, 2021 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-33372060

RESUMO

Correlated spontaneous activity plays critical role in the organization of neocortical circuits during development. However, cortical mechanisms regulating activity correlation are still elusive. In this study, using two-photon calcium imaging of the barrel cortex layer 4 (L4) in living neonatal mice, we found that NMDA receptors (NMDARs) in L4 neurons are important for enhancement of spontaneous activity correlation. Disruption of GluN1 (Grin1), an obligatory NMDAR subunit, in a sparse population of L4 neurons reduced activity correlation between GluN1 knock-out (GluN1KO) neuron pairs within a barrel. This reduction in activity correlation was even detected in L4 neuron pairs in neighboring barrels and most evident when either or both of neurons are located on the barrel edge. Our results provide evidence for the involvement of L4 neuron NMDARs in spatial organization of the spontaneous firing activity of L4 neurons in the neonatal barrel cortex.SIGNIFICANCE STATEMENT Precise wiring of the thalamocortical circuits is necessary for proper sensory information processing, and thalamus-derived correlated spontaneous activity is important for thalamocortical circuit formation. The molecular mechanisms involved in the correlated activity transfer from the thalamus to the neocortex are largely unknown. In vivo two-photon calcium imaging of the neonatal barrel cortex revealed that correlated spontaneous activity between layer four neurons is reduced by mosaic knock-out (KO) of the NMDA receptor (NMDAR) obligatory subunit GluN1. Our results suggest that the function of NMDARs in layer four neurons is necessary for the communication between presynaptic and postsynaptic partners during thalamocortical circuit formation.


Assuntos
Potenciais Pós-Sinápticos Excitadores/fisiologia , Proteínas do Tecido Nervoso/deficiência , Receptores de N-Metil-D-Aspartato/deficiência , Córtex Somatossensorial/citologia , Córtex Somatossensorial/metabolismo , Animais , Animais Recém-Nascidos , Feminino , Masculino , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos Knockout , Imagem Molecular/métodos , Proteínas do Tecido Nervoso/genética , Receptores de N-Metil-D-Aspartato/genética
14.
Nat Commun ; 11(1): 5171, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33057002

RESUMO

Excitatory and inhibitory neurons are connected into microcircuits that generate circuit output. Central in the hippocampal CA3 microcircuit is the mossy fiber (MF) synapse, which provides powerful direct excitatory input and indirect feedforward inhibition to CA3 pyramidal neurons. Here, we dissect its cell-surface protein (CSP) composition to discover novel regulators of MF synaptic connectivity. Proteomic profiling of isolated MF synaptosomes uncovers a rich CSP composition, including many CSPs without synaptic function and several that are uncharacterized. Cell-surface interactome screening identifies IgSF8 as a neuronal receptor enriched in the MF pathway. Presynaptic Igsf8 deletion impairs MF synaptic architecture and robustly decreases the density of bouton filopodia that provide feedforward inhibition. Consequently, IgSF8 loss impairs excitation/inhibition balance and increases excitability of CA3 pyramidal neurons. Our results provide insight into the CSP landscape and interactome of a specific excitatory synapse and reveal IgSF8 as a critical regulator of CA3 microcircuit connectivity and function.


Assuntos
Região CA3 Hipocampal/fisiologia , Proteínas de Transporte/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Proteínas de Membrana/metabolismo , Fibras Musgosas Hipocampais/metabolismo , Células Piramidais/fisiologia , Animais , Proteínas de Transporte/genética , Células Cultivadas , Células HEK293 , Humanos , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Técnicas de Patch-Clamp , Cultura Primária de Células , Proteômica , Ratos , Sinaptossomos/metabolismo
15.
Proc Natl Acad Sci U S A ; 117(33): 20254-20264, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32747543

RESUMO

Correlated activation of cortical neurons often occurs in the brain and repetitive correlated neuronal firing could cause long-term modifications of synaptic efficacy and intrinsic excitability. We found that repetitive optogenetic activation of neuronal populations in the mouse cortex caused enhancement of optogenetically evoked firing of local coactivated neurons as well as distant cortical neurons in both ipsilateral and contralateral hemispheres. This global enhancement of evoked responses required coactivation of a sufficiently large population of neurons either within one cortical area or distributed in several areas. Enhancement of neuronal firing was saturable after repeated episodes of coactivation, diminished by inhibition of N-methyl-d-aspartic acid receptors, and accompanied by elevated excitatory postsynaptic potentials, all consistent with activity-induced synaptic potentiation. Chemogenetic inhibition of neuronal activity of the thalamus decreased the enhancement effect, suggesting thalamic involvement. Thus, correlated excitation of large neuronal populations leads to global enhancement of neuronal excitability.


Assuntos
Potenciais de Ação/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina , Excitabilidade Cortical , Corantes Fluorescentes , Masculino , Camundongos , Rede Nervosa , Transmissão Sináptica/fisiologia
16.
Nat Commun ; 11(1): 3688, 2020 07 23.
Artigo em Inglês | MEDLINE | ID: mdl-32703948

RESUMO

Zeta inhibitory peptide (ZIP), a PKMζ inhibitor, is widely used to interfere with the maintenance of acquired memories. ZIP is able to erase memory even in the absence of PKMζ, via an unknown mechanism. We found that ZIP induces redistribution of the AMPARGluA1 in HEK293 cells and primary cortical neurons, and decreases AMPAR-mediated currents in the nucleus accumbens (NAc). These effects were mimicked by free arginine or by a modified ZIP in which all but the arginine residues were replaced by alanine. Redistribution was blocked by a peptidase-resistant version of ZIP and by treatment with the nitric oxide (NO)-synthase inhibitor L-NAME. ZIP increased GluA1-S831 phosphorylation and ZIP-induced redistribution was blocked by nitrosyl-mutant GluA1-C875S or serine-mutant GluA1-S831A. Introducing the cleavable arginine-alanine peptide into the NAc attenuated expression of cocaine-conditioned reward. Together, these results suggest that ZIP may act as an arginine donor, facilitating NO-dependent downregulation of AMPARs, thereby attenuating learning and memory.


Assuntos
Peptídeos Penetradores de Células/farmacologia , Condicionamento Psicológico/efeitos dos fármacos , Lipopeptídeos/farmacologia , Memória de Longo Prazo/efeitos dos fármacos , Óxido Nítrico/metabolismo , Receptores de AMPA/metabolismo , Animais , Cocaína/administração & dosagem , Regulação para Baixo , Endocitose/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Células HEK293 , Humanos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Camundongos , Modelos Animais , NG-Nitroarginina Metil Éster/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Óxido Nítrico/antagonistas & inibidores , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/fisiologia , Fosforilação , Cultura Primária de Células , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Ratos , Receptores de AMPA/genética , Recompensa , Técnicas Estereotáxicas
17.
Nat Commun ; 11(1): 3012, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32541656

RESUMO

The complex relationship between specific hippocampal oscillation frequency deficit and cognitive dysfunction in the ischemic brain is unclear. Here, using a mouse two-vessel occlusion (2VO) cerebral ischemia model, we show that visual stimulation with a 40 Hz light flicker drove hippocampal CA1 slow gamma and restored 2VO-induced reduction in CA1 slow gamma power and theta-low gamma phase-amplitude coupling, but not those of the high gamma. Low gamma frequency lights at 30 Hz, 40 Hz, and 50 Hz, but not 10 Hz, 80 Hz, and arrhythmic frequency light, were protective against degenerating CA1 neurons after 2VO, demonstrating the importance of slow gamma in cognitive functions after cerebral ischemia. Mechanistically, 40 Hz light flicker enhanced RGS12-regulated CA3-CA1 presynaptic N-type calcium channel-dependent short-term synaptic plasticity and associated postsynaptic long term potentiation (LTP) after 2VO. These results support a causal relationship between CA1 slow gamma and cognitive dysfunctions in the ischemic brain.


Assuntos
Região CA1 Hipocampal/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Ritmo Gama/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios/fisiologia , Animais , Isquemia Encefálica/fisiopatologia , Região CA1 Hipocampal/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Estimulação Elétrica , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora/fisiologia , Estimulação Luminosa
18.
Nat Neurosci ; 23(6): 741-753, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32393895

RESUMO

During sleep and awake rest, the neocortex generates large-scale slow-wave (SW) activity. Here, we report that the claustrum coordinates neocortical SW generation. We established a transgenic mouse line that enabled the genetic interrogation of a subpopulation of claustral glutamatergic neurons. These neurons received inputs from and sent outputs to widespread neocortical areas. The claustral neuronal firings mostly correlated with cortical SW activity. In vitro optogenetic stimulation of the claustrum induced excitatory postsynaptic responses in most neocortical neurons, but elicited action potentials primarily in inhibitory interneurons. In vivo optogenetic stimulation induced a synchronized down-state featuring prolonged silencing of neural activity in all layers of many cortical areas, followed by a down-to-up state transition. In contrast, genetic ablation of claustral neurons attenuated SW activity in the frontal cortex. These results demonstrate a crucial role of claustral neurons in synchronizing inhibitory interneurons across wide cortical areas for the spatiotemporal coordination of SW activity.


Assuntos
Claustrum/fisiologia , Neocórtex/fisiologia , Sono de Ondas Lentas/fisiologia , Potenciais de Ação/fisiologia , Animais , Potenciais Pós-Sinápticos Excitadores/fisiologia , Interneurônios/fisiologia , Camundongos , Camundongos Transgênicos , Inibição Neural/fisiologia , Neurônios/fisiologia , Optogenética , Proteínas com Domínio T/genética
19.
J Neurosci ; 40(26): 4972-4980, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32430294

RESUMO

Synaptic vesicles need to be recycled and refilled rapidly to maintain high-frequency synaptic transmission. However, little is known about the control of neurotransmitter transport into synaptic vesicles, which determines the contents of synaptic vesicles and the strength of synaptic transmission. Here, we report that Na+ substantially accumulated in the calyx of Held terminals of juvenile mice of either sex during high-frequency spiking. The activity-induced elevation of cytosolic Na+ activated vesicular Na+/H+ exchanger, facilitated glutamate loading into synaptic vesicles, and increased quantal size of asynchronous released vesicles but did not affect the vesicle pool size or release probability. Consequently, presynaptic Na+ increased the EPSCs and was required to maintain the reliable high-frequency signal transmission from the presynaptic calyces to the postsynaptic medial nucleus of the trapezoid body (MNTB) neurons. Blocking Na+/H+ exchange activity decreased the postsynaptic current and caused failures in postsynaptic firing. Therefore, during high-frequency synaptic transmission, when large amounts of glutamate are released, Na+ accumulated in the terminals, activated vesicular Na+/H+ exchanger, and regulated glutamate loading as a function of the level of vesicle release.SIGNIFICANCE STATEMENT Auditory information is encoded by action potentials (APs) phase-locked to sound frequency at high rates. A large number of synaptic vesicles are released during high-frequency synaptic transmission; accordingly, synaptic vesicles need to be recycled and refilled rapidly. We have recently found that a Na+/H+ exchanger expressed on synaptic vesicles promotes vesicle filling with glutamate. Here, we showed that when a large number of synaptic vesicles are released during high-frequency synaptic transmission, Na+ accumulates in axon terminals and facilitates glutamate uptake into synaptic vesicles. Na+ thus accelerates vesicle replenishment and sustains reliable synaptic transmission.


Assuntos
Ácido Glutâmico/metabolismo , Terminações Pré-Sinápticas/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Transmissão Sináptica/fisiologia , Vesículas Sinápticas/metabolismo , Animais , Encéfalo/metabolismo , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Transporte Proteico/fisiologia , Sódio/metabolismo
20.
Sci Rep ; 10(1): 8626, 2020 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-32451470

RESUMO

The study of postsynaptic excitation to inhibition (E/I ratio) imbalances in human brain diseases, is a highly relevant functional measurement poorly investigated due to postmortem degradation of synaptic receptors. We show that near-simultaneous recording of microtransplanted synaptic receptors after simulated morgue conditions allows the determination of the postsynaptic E/I ratio for at least 120 h after death, expanding the availability and use of human diseased tissue stored in brain banks.


Assuntos
Encéfalo/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Potenciais Pós-Sinápticos Inibidores/fisiologia , Adulto , Animais , Encefalopatias/patologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Humanos , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Ácido Caínico/farmacologia , Masculino , Oócitos/citologia , Oócitos/metabolismo , Ratos , Ratos Wistar , Receptores de Neurotransmissores/metabolismo , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/fisiologia , Temperatura , Fatores de Tempo , Ácido gama-Aminobutírico/farmacologia
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