Glutamatergic Research Articles

DMD-10 is dispensable for the initial development of amphid sensory neurons and their survival in mature C. elegans.

Mechanosensory or chemosensory activation of glutamatergicASH amphid sensory neurons promotes avoidancebehaviors in C. elegans. Wormswith mutations in the transcription factor DMD-10 have impaired ASH-mediated sensorimotor reflexes. We hypothesized that the behavioral dysfunction in dmd-10 mutants could arise from impaired ASH development or survival leading to disrupted glutamatergic signaling.To test this, we performed in vivo fluorescence microscopy of young adult C. elegans amphid neurons after labeling with the lipophilic dye DiI. We quantified the number of ASH neurons as well as five other amphid sensory neuron pairs. We found that the number of amphid neurons in dmd-10 mutants was the same as in wild-type worms. Our results suggest that dmd-10 is not required for amphid neuron development or survival in mature C. elegans.

Supramammillary neurons projecting to the septum regulate dopamine and motivation for environmental interaction in mice

The supramammillary region (SuM) is a posterior hypothalamic structure, known to regulate hippocampal theta oscillations and arousal. However, recent studies reported that the stimulation of SuM neurons with neuroactive chemicals, including substances of abuse, is reinforcing. We conducted experiments to elucidate how SuM neurons mediate such effects. Using optogenetics, we found that the excitation of SuM glutamatergic (GLU) neurons was reinforcing in mice; this effect was relayed by their projections to septal GLU neurons. SuM neurons were active during exploration and approach behavior and diminished activity during sucrose consumption. Consistently, inhibition of SuM neurons disrupted approach responses, but not sucrose consumption. Such functions are similar to those of mesolimbic dopamine neurons. Indeed, the stimulation of SuM-to-septum GLU neurons and septum-to-ventral tegmental area (VTA) GLU neurons activated mesolimbic dopamine neurons. We propose that the supramammillo-septo-VTA pathway regulates arousal that reinforces and energizes behavioral interaction with the environment.

Sym-2 loss-of-function causes glutamatergic neurodegeneration after oxidative stress.

Although some RNA-binding proteins are known to contribute to neurodegeneration, the genetic interaction between the genes encoding these proteins is unclear. Here, we examine the interaction between sym-2, the gene encoding an ortholog of hnRNPF and hnRNPH, and hrpa-1, the ortholog of of the gene encoding hnRNPA2, which when mutated causes multisystem proteinopathy. We find that after 22 hours, but not 4 hours, of paraquat-induced oxidative stress, sym-2(mn617) has a mild glutamatergic neurodegeneration phenotype. Interestingly, this defect is rescued by expression of chimeric WT hrpa-1, but not mutant. Thus, we identify a curious genetic interaction between sym-2 and hrpa-1.

Kemirgen Hipotalamusunda Glutamatın Atriyal Natriüretik Peptit Nöronları Üzerindeki Etkilerinin İmmünohistokimyasal Yöntemle Araştırılması

Atriyal natriüretik peptit (ANP) organizmanın sıvı homeostazında önemli etkileri olan, özellikle de kan basıncı ile sıvı elektrolit dengesinin düzenlenmesinde rol oynayan bir peptittir. Yoğun olarak atrial kalp kası hücrelerince üretilen ANP, merkezi sinir siteminde (MSS) lokalize bir grup nöron tarafından da eksprese edilir. MSS’de nöronal ağlarda impuls iletiminde çok önemli rolü olan glutamaterjik sistemin ANP nöronlarını kontrol eden etkileri ile ilgili bilgi literatürde yer almamaktadır. Sunulan çalışma kapsamında, hipotalamusun supraoptik çekirdeğinde lokalize ANP nöronları üzerinde glutamat agonistlerinin etkileri ve bu nöronlarda eksprese olan glutamat reseptör alt birimlerinin varlığı, ikili immünoperoksidaz ve immünoflouresans yöntemler kullanılarak araştırılmıştır. Glutamat agonistlerinin etkilerini belirlemek üzere, kainik asit, AMPA ve NMDA, kontrol grupları için salin, antagonist olarak CNQX ve MK801 enjeksiyonu yapılan sıçanları içeren deney grupları oluşturulmuştur. ANP nöronlarındaki glutamaterjik innervasyonun belirlenmesinde veziküler glutamat transporter (VGluT) proteinleri ve nöronal aktivasyonun gösterilmesinde ise c-Fos immünoreaktivitesinin varlığı belirteç olarak kullanılmıştır. Çalışmaların sonucunda; glutamat agonistlerinin ANP nöronlarında nöronal aktivasyonu anlamlı bir şekilde arttırdığı, bu artışın antagonistler ile anlamlı bir şekilde baskılanabildiği belirlenmiştir. Ayrıca ANP nöronlarının glutamat reseptörlerine ait alt birimlerden GluA1, GluA2, GluK1/2/3 ve GluK5’i eksprese ettikleri ve VGluT içeren glutamaterjik akson sonlanmalarıyla temasta oldukları saptanmıştır. Sonuç olarak, bu çalışma ile glutamatın ANP nöronlarında aktive edici etkiye sahip olduğu ve glutamat reseptörlerinin bu nöronlarca eksprese edildiği, dolayısıyla da bu nöronların glutamaterjik uyarıları alabilecek mekanizmaya sahip oldukları gösterilmiştir. Bu sonuçlar, ANP nöronlarının merkezi düzenlenmesinde glutamaterjik sistemin önemli bir rol oynayabileceğini düşündürmüştür.

Glutamatergic transmission regulates locomotory behavior on a food patch in C. elegans.

Glutamatergic transmission regulates locomotory behavior on a food patch in C. elegans.

Co-expression of glutamatergic and autism-related genes in the hippocampus of male mice with disturbances of social behavior

В настоящее время существует представление о вовлеченности глутаматергической системы (ГГ) в механизмы развития аутизма. В предыдущих исследованиях нами было показано, что негативный социальный опыт, приобретенный в ежедневных межсамцовых конфронтациях, приводит к нарушениям в социальном поведении: снижению коммуникативности, нарушению социализации, появлению стереотипных форм поведения, которые могут рассматриваться как симптомы аутистического спектра. В связи с этим целью нашей работы было изучение с помощью транскриптомного анализа изменений экспрессии генов, кодирующих белки, вовлеченные в функционирование глутаматергической системы, и генов, связанных с патологией аутизма (ГА), в гиппокампе. В эксперименте использовали животных с нарушениями социального поведения, вызванными повторным опытом социальных побед или поражений в ежедневных агонистических взаимодействиях. Для формирования групп животных с контрастными типами поведения использовали модель сенсорного контакта (хронического социального стресса). Полученные образцы мозга были секвенированы в ЗАО «Геноаналитика» (http://genoanalytica.ru/, Россия, Москва). Транскриптомный анализ показал, что у агрессивных животных снижается экспрессия генов Shank3, Auts2, Ctnnd2, Nrxn2, для которых показано участие в развитии аутизма, а также глутаматергического гена Grm4. В то же время у животных с негативным социальным опытом экспрессия ГА Shank2, Nlgn2, Ptcdh10, Reln, Arx возрастает. При этом ГГ (Grik3, Grm2, Grm4, Slc17a7, Slc1a4, Slc25a22), за исключением гена Grin2a, повышают свою экспрессию. Корреляционный анализ выявил статистически значимую взаимосвязь из- мененной экспрессии ГГ и ГА. Полученные результаты, с одной стороны, могут служить подтверждением участия ГГ в патофизиологии развития симптомов аутистического спектра, с другой – свидетельствовать о коэкспрессии ГГ и ГА в гиппокампе, развивающейся под влиянием социальной среды. Так как большинство ГА, изменивших экспрессию в настоящем исследовании, являются генами, связанными с клеточным скелетом и внеклеточным матриксом, в частности участвующими в формировании синапсов, а ГГ, изменившие свою экспрессию, – генами, кодирующими субъединицы рецепторов, то можно предположить, что вовлечение ГГ в патофизиологию аутизма происходит на уровне рецепторов.

Different coding strategy of sound information between GABAergic and glutamatergic neurons in the auditory midbrain.

In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, how the sound is coded by distinct cell types is largely unknown. Large GABAergic cells are tuned broadly to pure tones and respond more strongly to frequency-modulated sweeps than small GABAergic and glutamatergic (GLU) cells. Neurons, especially GLU cells, which share sharpness of tuning and sweep sensitivity, were spatially clustered inside the ICC. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. The results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of cells, and contributes information coding in higher centres in different ways. The rules governing the encoding of sound information in the higher auditory centres are largely unknown. In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, the presence of functional maps other than tonotopicity has been suggested but not established, due to significant heterogeneity in the response properties of single microdomains. Since each ICC cell type has distinct neuronal circuitry, each cell type might encode sound information differently. Here, juxtacellular recording from rat ICC of both sexes revealed that large GABAergic (LG), small GABAergic (SG) and glutamatergic (GLU) cells encode sound information differently. LG cells are broadly tuned and respond more strongly to frequency-modulated sweeps than SG and GLU cells. At a population level, responsiveness to sweeps is location dependent: the responsiveness to sweeps is shared in local clusters of GLU cells, whereas that to directional selectivity of sweeps is shared in local clusters of LG cells. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. LG neurons had a dense local axonal plexus with projection fibres to multiple distant targets, whereas GLU projection neurons mainly aimed at a single, distant target and had less dense local collaterals. These results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of the cell, and the different cell types contribute information coding in higher centres in different ways.

The ventromedial hypothalamic circuitry and male alloparental behaviour in a socially monogamous rodent species.

As prairie voles (Microtus ochrogaster) display spontaneous biparental care, and the ventromedial hypothalamus (VMH) has been implicated in reproductive behaviour, we conducted experiments to test the hypothesis that the VMH neurochemical circuitry is involved in alloparental behaviours in male prairie voles. We compared alloparental behaviours of adult, sexually naïve male and female voles-both displayed licking/grooming, huddling and retrieving behaviours towards conspecific pups. We also stained for the immediate-early gene encoded early growth protein Egr-1 in the vole brain. The pup-exposed animals showed levels of Egr-1 staining that was higher in the VMH but lower in the amygdala compared to animals exposed to a pup-sized piece of plastic (control). A retrograde tracer, Fluoro-Gold (FG), was injected into the VMH of male voles that were subsequently tested in the pup exposure or control condition. More FG/Egr-1 cells were detected for glutamatergic (GLU) staining in the ventral bed nucleus of the stria terminalis (BNSTv) and medial amygdala (MeA), whereas less FG/Egr-1 cells were stained for gamma-aminobutyric acid (GABA) in the MeA of the pup-exposed group compared to the control group. Further, the ratio of GLU:GABA expression in FG/Egr-1 projection neurons from both the BNSTv and MeA to the VMH was increased following pup exposure. Finally, pharmacological blockade of either dopamine D1 receptor or oxytocin receptor in the VMH impaired the onset of male alloparental behaviour. Together, these data suggest that the VMH may be involved in the onset of alloparental care and play a role in regulating social approach in male prairie voles.

The contribution of ionotropic gabaergic and N-methyl-D-Aspartic acid receptors in the antidepressant-like effects of hispidulin

Background: Salvia triloba, commonly known as sage belongs to Lamiaceae family, is conventionally used as a brain-enhancing tonic. The purpose of this study was to evaluate hispidulin, a flavonoid isolated from S. triloba for its antidepressant-like effects and to identify its possible mechanisms of action. Materials and Methods: Mouse models of the forced swimming test (FST) and tail-suspension test (TST) were used to assess the antidepressant-like effects of hispidulin. Results: The results showed that hispidulin at the doses level of 1–10 mg/kg, intraperitoneal (ip) exerted significant antidepressant-like effects in both FST and TST. Pretreatment of animals with bicuculline (4 mg/kg, ip; a competitive γ-aminobutyric acid (GABA) antagonist) and N-methyl-D-aspartic acid (NMDA) (75 mg/kg, ip, glutamate receptor agonist) significantly blocked the reduction in immobility time of mice treated with hispidulin (3 mg/kg, ip) in FST. Furthermore, brain GABA levels were significantly decreased by coadministration of hispidulin with bicuculline, whereas glutamate levels were increased with combined administration of hispidulin and NMDA. Moreover, coadministration of sub-effective doses of hispidulin (0.5 mg/kg, ip) and ketamine (0.3 mg/kg, ip) or MK 801 (0.1 mg/kg, ip) also exerted significant antidepressant-like effects in FST. Conclusion: Taken together, these findings suggest that hispidulin possess significant antidepressant-like effects mediated most likely through GABAergic and glutamatergic mechanisms.

Comparative Sensitivity of Human-Induced Pluripotent Stem Cell-Derived Neuronal Subtypes to Chemically Induced Neurodegeneration

Abstract Introduction: Development of an in vitro screening assay to predict the neurodegenerative potential of compounds in humans would benefit the safety assessment of pharmaceuticals and industrial chemicals. In this study, we compared the sensitivity of physiologically relevant human-induced pluripotent stem cell-derived GABAergic (GABA) and glutamatergic (GLUTA) neurons to chemically induced perturbation of morphological endpoints of neurite outgrowth to evaluate potential lineage-specific neurodegeneration. Materials and Methods: GABA and GLUTA neurons were treated for 24 hours with 0.1–100 μM of 10 chemicals (acetaminophen [negative control], bisindolylmaleimide-1, colchicine, dexamethasone, diazinon, doxorubicin, 1-methyl-4-phenylpyridinium, paclitaxel, rotenone, U0126) with known neurodegenerative effects in vitro, and then immunofluorescent cells were analyzed using automated high-content imaging analysis to measure neurite outgrowth endpoints. Results: No effect on any endpoint was observed wi...

A review on the role of γ-aminobutyric acid signaling pathway in autism spectrum disorder

The etiology and pathogenesis of autism spectrum disorder (ASD) are not yet clear. Studies have shown that there are many neurotransmitter abnormalities in children with ASD, mainly involving in glutamate, γ-aminobutyric acid (GABA), dopamine, 5-HT and oxytocin. The imbalance of excitatory glutamatergic neurotransmitters and inhibitory GABAergic neurotransmitters is closely related to the pathogenesis of ASD. Both animal model studies and clinical studies on ASD suggest that GABA signaling pathway may play an important role in the pathogenesis of ASD. This article reviews the research on the association between GABA signaling pathway and the pathogenesis of ASD to further explore the pathogenesis of ASD and provide theoretical basis for the treatment of ASD.

Glutamatergic disturbance after arthroscopy in the non- elderly patients with or without chronic pain: a magnetic resonance spectroscopy study

Objective Patients with joint disease are often plagued by chronic pain and arthroscopy is an effective and minimally invasive procedure for diagnosis and treatment. But long- term painful torture may cause the change for brain structure and function. This study sought to evaluate the effect of long- term pain on brain metabolism. Methods This study was a prospective cohort study performed between August 2016 and December 2016. Patients were subjected to arthroscopic surgery for joint diseases. A visual analog scale (VAS) was used to measure pain intensity. The magnetic resonance spectroscopy (MRS) was used to identify the concentration of neuro- metabolites in the periaqueductal gray (PAG) and medial prefrontal cortex (mPFC) before and after arthroscopies. Results Eight patients with chronic pain and 7 without chronic pain were enrolled. The mean age was 32 years ole. In the patients with chronic pain, glutamic acid and glutamine (Glx) in PAG were elevated after operation (1.64±0.46 vs. 1.22±0.23). The patients with chronic pain had a higher post- operation Glx of PAG than controls (1.64±0.46 vs. 1.21±0.19). Conclusion There was a glutamatergic disturbance after arthroscopy in the non- elderly patients with chronic pain. Key words: Chronic pain; Arthroscopy; Joint disease; Magnetic resonance spectroscopy; Periaqueductal gray

4. Glutamatergic Findings in Schizophrenia: How to Make Sense of Them?

4. Glutamatergic Findings in Schizophrenia: How to Make Sense of Them?

Immunohistochemical characterization of axon terminals of the adult rat cerebellar cortex

Aim of the present study was to immunohystochemically characterize the glutamatergic terminals in the cerebellar cortex. The study was carried out on adult rat, using immunohistochemistry for the vesicular transporters of glutamate, VGLUT1 e VGLUT2, and synaptophysin. Results. Terminals positive for VGLUT1 e VGLUT2 were observed in the molecular layer (ML) and granular layer (GL). ML. VGLUT1-positive terminals appeared very numerous, homogeneously distributed throughout the layer with a distribution pattern resembling that of the parallel fiber terminals. VGLUT2-positive terminals appeared displaced along distinct spiral lines extending from the deeper part of the layer up to the its superficial part, likely corresponding to synapses between climbing fibers and Purkinje neuron dendrites. No colocalization of VGLUT1 and VGLUT2 was observed in ML. Double labelling for VGLUT1 and synaptophysin and, respectively, VGLUT2 and synaptophysin revealed colocalization, suggesting the axon terminal nature of the immunolabelled elements. Interestingly, some elements appeared synaptophysin positive, but negative for VGLUT1 and VGLUT2. In GL, VGLUT1 and VGLUT2 positive terminals displayed similar distribution patterns, They appeared clustered in restricted regions of the layer, scattered within granule neurons, at the level of synaptic glomeruli. Most of these terminals showed a colocalization of VGLUT1 and VGLUT2. However a part of them shows positivity for VGLUT2 and negativity for VGLUT1. All the VGLUT1 and VGLUT2 positive elements also displayed positivity for synaptophysin. Finally, like in ML, some elements appeared synaptophysin positive, but negative for VGLUT1 and VGLUT2. Conclusion. The results indicate that the glutamatergic terminals in the cerebellar cortex may be differentiated combining Immunohistochemistry for VGLUT1 and VGLUT2. Moreover, the results identify subpopulations within terminals of the parallel, climbing and mossy fibers. In particular, a subpopulation of mossy fiber terminals, displaying positivity for VGLUT2 and negativity for VGLUT1, are different from the vast majority of mossy fiber terminals, which display for both VGLUT1 and VGLUT2, but similar to climbing fiber terminals. It is intriguing to hypothesize that these mossy fibers may constitute a contingent of mossy fiber originated in the inferior olivary nuclear complex.

Adding Glutamatergic Medications to Antidepressants in OCD: A Meta-Analysis

Current pharmaceutical treatments for obsessive-compulsive disorder (OCD) are limited to serotonergic antidepressants and augmentation with atypical

P.3.002 Glutamatergic and GABAergic gene-sets in ADHD: association to overlapping traits in ADHD and autism

P.3.002 Glutamatergic and GABAergic gene-sets in ADHD: association to overlapping traits in ADHD and autism

Painting a global picture of basal ganglia network: from past to present!

Since the 70s it has been thought that basal ganglia integrated sensorimotor, associative and limbic inputs and then projected this information through the thalamus to the motor cortex, supplementary motor area and frontal cortex, thus playing a relevant role in planning movement. Recent literature on basal ganglia networks is going beyond the classical “dogma” of dorsal striatum as the main station for cortical inputs in basal ganglia loops and several neurophysiological studies have suggested a more segregated organization of these neural circuits. In the classical view, various tract-tracing methods combined with immunohistochemistry and in situ hybridization demonstrated that the cortical information flows through the basal ganglia via a dual-network model, based on the “direct” and “indirect” routes. However, in addition to these two major projection systems, a glutamatergic hyper-direct pathway between cerebral cortex and subthalamic nucleus has been demonstrated first in monkeys and then in humans. Furthermore, we have recently shown a i) cortico-pallidal connection; ii) a cerebello-pallidal connection; iii) a cerebello nigral connection [1, 2]. Herein, we extensively examined basal ganglia network of fifteen healthy subjects by using probabilistic constrained spherical deconvolution tractography on magnetic resonance diffusion weighted imaging data and we also performed weighted connectivity analysis for each of the subcortical nuclei. In addition, we demonstrated for the first time tractographic evidences of the existence of a direct cortico-nigral pathway in humans. We found that substantia nigra is connected with cerebral cortex as a whole, with the most representative connections involving prefrontal cortex, precentral and postcentral gyri and superior parietal lobule. These findings would strength the hypothesis that the cortico-basal ganglia network consists of several, parallel, segregated, and functionally distinct, but homologous loop, and may be relevant for the comprehension of the pathophysiology of several basal ganglia disorders.

The role of postsynaptic density proteins in neural degeneration and regeneration

The structure, function and plasticity of excitatory glutamatergic synapses in the brain are significantly altered by neurodevelopmental and neurodegenerative disorders (Grabrucker et al., 2011; Fourie et al., 2014; Musardo et al., 2014; Lee et al., 2015), resulting in impairments in cognition, learning, memory, motor and sensory function. Reversing these synaptic deficits is a major challenge for neuroscience, and significant research has focussed on glutamate receptors as therapeutic targets but human trials have shown little success. Recently, attention has turned to proteins localized to the postsynaptic density (PSD) of excitatory synapses, as these proteins control the trafficking and targeting of glutamate receptors at synapses. Not surprisingly, PSD proteins have been shown to be altered in human and rodent models of neurological disorders, suggesting changes in their expression during the disease process (Grabrucker et al., 2011; Fourie et al., 2014; Musardo et al., 2014; Mei et al., 2016). However, the sheer number of these proteins, each with unique splice variations and developmental expression profiles, raises the possibility that targeted expression of specific PSD protein subfamilies within defined time windows has significant therapeutic potential. Indeed rescue of normal social behaviour has recently been observed in adulthood in an autism rodent model by re-expression of SHANK3, which encodes a major PSD protein, yet rescue of anxiety and motor coordination deficits required SHANK3 re-expression earlier in development (Mei et al., 2016). Peptide disruption of PSD protein interactions with glutamate receptors is also showing promise to reduce excitotoxicity and ischaemic damage in stroke models (Zhou et al., 2015). Increasing our knowledge of the potential of these proteins in human neurons is the next important step, as this will be key to determining their true therapeutic potential for neuroregeneration.

Substantial DNA methylation differences between two major neuronal subtypes in human brain.

The brain is built from a large number of cell types which have been historically classified using location, morphology and molecular markers. Recent research suggests an important role of epigenetics in shaping and maintaining cell identity in the brain. To elucidate the role of DNA methylation in neuronal differentiation, we developed a new protocol for separation of nuclei from the two major populations of human prefrontal cortex neurons—GABAergic interneurons and glutamatergic (GLU) projection neurons. Major differences between the neuronal subtypes were revealed in CpG, non-CpG and hydroxymethylation (hCpG). A dramatically greater number of undermethylated CpG sites in GLU versus GABA neurons were identified. These differences did not directly translate into differences in gene expression and did not stem from the differences in hCpG methylation, as more hCpG methylation was detected in GLU versus GABA neurons. Notably, a comparable number of undermethylated non-CpG sites were identified in GLU and GABA neurons, and non-CpG methylation was a better predictor of subtype-specific gene expression compared to CpG methylation. Regions that are differentially methylated in GABA and GLU neurons were significantly enriched for schizophrenia risk loci. Collectively, our findings suggest that functional differences between neuronal subtypes are linked to their epigenetic specification.

The Modulatory Role of Dopamine in Anxiety-like Behavior.

Anxiety is an unpleasant physiological state in which an overreaction to a situation occurs. It has been suggested that different brain regions are involved in the modulation and expression of anxiety, including the amygdala, hippocampus, and frontal cortex. Dysfunction of neurotransmitters and their receptors can lead to many mood disorders like anxiety. There are evidences that dopamine plays an important role in anxiety modulation in different parts of the brain. Some evidence has shown that the mesolimbic, mesocortical and nigrostriatal dopaminergic system are involved in anxiety. Both dopamine D1 and D2 receptor mechanisms are important in mediating anxiety. The activity of dopaminergic system is modulated by several neurotransmitters, including glutamatergic neurons from the medial prefrontal cortex (mPFC), GABAergic fibers from the nucleus accumbens (NAc) as well as the ventral pallidum and cholinergic fibers from the pedunculopontine nucleus and the laterodorsal tegmental nucleus. Thus, changes in the glutamatergic, and GABAergic, as well as mediated transmission in the mesolimbic, mesocortical and nigrostriatal dopaminergic system may influence anxiety-like behavior.