The Experts below are selected from a list of 87285 Experts worldwide ranked by ideXlab platform
Michael R. Vasko - One of the best experts on this subject based on the ideXlab platform.
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Epac activation sensitizes rat Sensory Neurons through activation of Ras.
Molecular and Cellular Neuroscience, 2015Co-Authors: Behzad Shariati, Grant D Nicol, Eric L. Thompson, Michael R. VaskoAbstract:Abstract Guanine nucleotide exchange factors directly activated by cAMP (Epacs) have emerged as important signaling molecules mediating persistent hypersensitivity in animal models of inflammation, by augmenting the excitability of Sensory Neurons. Although Epacs activate numerous downstream signaling cascades, the intracellular signaling which mediates Epac-induced sensitization of capsaicin-sensitive Sensory Neurons remains unknown. Here, we demonstrate that selective activation of Epacs with 8-CPT-2′-O-Me-cAMP-AM (8CPT-AM) increases the number of action potentials (APs) generated by a ramp of depolarizing current and augments the evoked release of calcitonin gene-related peptide (CGRP) from isolated rat Sensory Neurons. Internal perfusion of capsaicin-sensitive Sensory Neurons with GDP-βS, substituted for GTP, blocks the ability of 8CPT-AM to increase AP firing, demonstrating that Epac-induced sensitization is G-protein dependent. Treatment with 8CPT-AM activates the small G-proteins Rap1 and Ras in cultures of Sensory Neurons. Inhibition of Rap1, by internal perfusion of a Rap1-neutralizing antibody or through a reduction in the expression of the protein using shRNA does not alter the Epac-induced enhancement of AP generation or CGRP release, despite the fact that in most other cell types, Epacs act as Rap-GEFs. In contrast, inhibition of Ras through expression of a dominant negative Ras (DN-Ras) or through internal perfusion of a Ras-neutralizing antibody blocks the increase in AP firing and attenuates the increase in the evoked release of CGRP induced by Epac activation. Thus, in this subpopulation of nociceptive Sensory Neurons, it is the novel interplay between Epacs and Ras, rather than the canonical Epacs and Rap1 pathway, that is critical for mediating Epac-induced sensitization.
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Navβ4 regulates fast resurgent sodium currents and excitability in Sensory Neurons
Molecular pain, 2015Co-Authors: Cindy Barbosa, Michael R. Vasko, Zhi‑yong Tan, Ruizhong Wang, Wenrui Xie, Judith A. Strong, Reesha R. Patel, Jun-ming Zhang, Theodore R. CumminsAbstract:Background Increased electrical activity in peripheral Sensory Neurons including dorsal root ganglia (DRG) and trigeminal ganglia Neurons is an important mechanism underlying pain. Voltage gated sodium channels (VGSC) contribute to the excitability of Sensory Neurons and are essential for the upstroke of action potentials. A unique type of VGSC current, resurgent current (INaR), generates an inward current at repolarizing voltages through an alternate mechanism of inactivation referred to as open-channel block. INaRs are proposed to enable high frequency firing and increased INaRs in Sensory Neurons are associated with pain pathologies. While Nav1.6 has been identified as the main carrier of fast INaR, our understanding of the mechanisms that contribute to INaR generation is limited. Specifically, the open-channel blocker in Sensory Neurons has not been identified. Previous studies suggest Navβ4 subunit mediates INaR in central nervous system Neurons. The goal of this study was to determine whether Navβ4 regulates INaR in DRG Sensory Neurons.
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Lipid mediators of sensitivity in Sensory Neurons
Trends in pharmacological sciences, 2005Co-Authors: Kellie A. Park, Michael R. VaskoAbstract:Growing evidence implicates an increasing number of novel lipids, including eicosanoids, diacylglycerols, lysophosphatidic acids and ceramides, in augmenting the sensitivity of Sensory Neurons and enhancing pain perception. Many of these lipids are second messengers in signaling pathways that are associated with increasing the sensitivity of Sensory Neurons, whereas others are putative inflammatory mediators that activate either surface receptors or ion channels in these Neurons. Based on the studies we review, it is clear that lipid-derived inflammatory mediators are a novel group of targets for therapeutics to treat inflammation and chronic pain states. However, much work remains to define the roles of these lipids in inflammation and the cellular mechanisms by which they alter the sensitivity of Sensory Neurons.
Paul Fernyhough - One of the best experts on this subject based on the ideXlab platform.
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neurotrophin 3 prevents mitochondrial dysfunction in Sensory Neurons of streptozotocin diabetic rats
Experimental Neurology, 2005Co-Authors: Tze Jen Huang, N M Sayers, Alexei Verkhratsky, Paul FernyhoughAbstract:Sensory Neurons from streptozotocin (STZ)-diabetic rats exhibit depolarization of mitochondria and the related induction of reactive oxygen species has been proposed to contribute to the etiology of Sensory polyneuropathy in diabetes. There is deficient neurotrophin-3 (NT-3)-dependent neurotrophic support of Sensory Neurons in diabetes and treatment of STZ-diabetic rats with NT-3 prevents neuropathological alterations in peripheral nerve. Therefore, we hypothesized that loss of NT-3 may contribute to mitochondrial dysfunction in Sensory Neurons in diabetic Sensory neuropathy. The specific aim of this study was to determine whether treatment of STZ-diabetic rats with systemic NT-3 could prevent depolarization of the mitochondrial inner membrane potential (Δψm). In vitro studies with cultured DRG Neurons from control rats revealed that treatment with 50 ng/ml NT-3 for 6 h enhanced the Δψm, e.g., a higher polarized membrane potential, compared to untreated Neurons (P < 0.05). Studies on DRG Sensory Neurons from control vs. STZ-diabetic rats demonstrated that NT-3 therapy prevented the diabetes-induced depolarization of Δψm (P < 0.05) in parallel with normalization of diabetes-dependent deficits in Sensory nerve conduction velocity. Furthermore, alterations in mitochondrial function in vitro and in vivo correlated with the level of activation/expression of Akt in DRG Neurons.
Qizhi Gong - One of the best experts on this subject based on the ideXlab platform.
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Culture of mouse olfactory Sensory Neurons.
Current protocols in neuroscience, 2012Co-Authors: Qizhi GongAbstract:Olfactory Sensory Neurons, located in the nasal epithelium, detect and transmit odorant information to the central nervous system. This requires that these Neurons form specific neuronal connections within the olfactory bulb and express receptors and signaling molecules specific for these functions. This protocol describes a primary olfactory Sensory neuron culture technique that allows in vitro investigation of olfactory Sensory neuron differentiation, axon outgrowth, odorant receptor expression, and function. Olfactory epithelium is obtained from the nasal cavity and is enzymatically treated to reduce stroma tissue. Dissociated olfactory Sensory Neurons are cultured directly on a layer of cortical astrocytes to support their survival. Using this method, cultured olfactory Sensory Neurons maintain their bipolar morphology and express odorant signal transduction molecules, which are specific for olfactory Sensory Neurons.
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Current Protocols in Neuroscience - Culture of mouse olfactory Sensory Neurons.
Current Protocols in Neuroscience, 2012Co-Authors: Qizhi GongAbstract:Olfactory Sensory Neurons, located in the nasal epithelium, detect and transmit odorant information to the central nervous system. This requires that these Neurons form specific neuronal connections within the olfactory bulb and express receptors and signaling molecules specific for these functions. This protocol describes a primary olfactory Sensory neuron culture technique that allows in vitro investigation of olfactory Sensory neuron differentiation, axon outgrowth, odorant receptor expression and function. Olfactory epithelium is obtained from the nasal cavity and enzymatically treated to reduce stroma tissue. Dissociated olfactory Sensory Neurons are cultured directly on a layer of cortical astrocytes to support their survival. Using this method, cultured olfactory Sensory Neurons maintain their bipolar morphology and express odorant signal transduction molecules which are specific for olfactory Sensory Neurons.
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Expressing exogenous functional odorant receptors in cultured olfactory Sensory Neurons
Neural development, 2008Co-Authors: Huaiyang Chen, Sepehr Dadsetan, Alla F. Fomina, Qizhi GongAbstract:Background: Olfactory discrimination depends on the large numbers of odorant receptor genes and differential ligand-receptor signaling among Neurons expressing different receptors. In this study, we describe an in vitro system that enables the expression of exogenous odorant receptors in cultured olfactory Sensory Neurons. Olfactory Sensory Neurons in the culture express characteristic signaling molecules and, therefore, provide a system to study receptor function within its intrinsic cellular environment. Results: We demonstrate that cultured olfactory Sensory Neurons express endogenous odorant receptors. Lentiviral vector-mediated gene transfer enables successful ectopic expression of odorant receptors. We show that the ectopically expressed mouse I7 is functional in the cultured olfactory Sensory Neurons. When two different odorant receptors are ectopically expressed simultaneously, both receptor proteins co-localized in the same olfactory Sensory Neurons up to 10 days in vitro. Conclusion: This culture technique provided an efficient method to culture olfactory Sensory Neurons whose morphology, molecular characteristics and maturation progression resembled those observed in vivo. Using this system, regulation of odorant receptor expression and its ligand specificity can be studied in its intrinsic cellular environment.
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Conditional ablation of mature olfactory Sensory Neurons mediated by diphtheria toxin receptor
Journal of Neurocytology, 2005Co-Authors: Huaiyang Chen, Kenji Kohno, Qizhi GongAbstract:The vertebrate olfactory epithelium provides an excellent model system to study the regulatory mechanisms of neurogenesis and neuronal differentiation due to its unique ability to generate new Sensory Neurons throughout life. The replacement of olfactory Sensory Neurons is stimulated when damage occurs in the olfactory epithelium. In this study, transgenic mice, with a transgene containing human diphtheria toxin receptor under the control of the olfactory marker protein promoter (OMP-DTR), were generated in which the mature olfactory Sensory Neurons could be specifically ablated when exposed to diphtheria toxin. Following diphtheria toxin induced neuronal ablation, we observed increased numbers of newly generated growth associated protein 43 (GAP43)-positive immature olfactory Sensory Neurons. OMP-positive Neurons were continuously produced from the newly generated GAP43-positive cells. The expression of the signal transduction components adenylyl cyclase type III and the G-protein α subunit G_α olf was sensitive to diphtheria toxin exposure and their levels decreased dramatically preceding the disappearance of the OMP-positive Sensory Neurons. These data validate the hypothesis that OMP-DTR mice can be used as a tool to ablate the mature olfactory Sensory Neurons in a controlled fashion and to study the regulatory mechanisms of the neuronal replacement.
Kristin K Baldwin - One of the best experts on this subject based on the ideXlab platform.
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Selective conversion of fibroblasts into peripheral Sensory Neurons
Nature Neuroscience, 2015Co-Authors: Joel W Blanchard, Kevin T Eade, Attila Szűcs, Valentina Lo Sardo, Rachel K Tsunemoto, Daniel Williams, Pietro Paolo Sanna, Kristin K BaldwinAbstract:Humans and mice detect pain, itch, temperature, pressure, stretch and limb position via signaling from peripheral Sensory Neurons. These Neurons are divided into three functional classes (nociceptors/pruritoceptors, mechanoreceptors and proprioceptors) that are distinguished by their selective expression of TrkA, TrkB or TrkC receptors, respectively. We found that transiently coexpressing Brn3a with either Ngn1 or Ngn2 selectively reprogrammed human and mouse fibroblasts to acquire key properties of these three classes of Sensory Neurons. These induced Sensory Neurons (iSNs) were electrically active, exhibited distinct Sensory neuron morphologies and matched the characteristic gene expression patterns of endogenous Sensory Neurons, including selective expression of Trk receptors. In addition, we found that calcium-imaging assays could identify subsets of iSNs that selectively responded to diverse ligands known to activate itch- and pain-sensing Neurons. These results offer a simple and rapid means for producing genetically diverse human Sensory Neurons suitable for drug screening and mechanistic studies. In this study, the authors show that expression of Brn3a with Ngn1 or 2 can induce the direct reprogramming of mouse and human fibroblasts into peripheral Sensory Neurons. They further demonstrate that these Neurons exhibit the expression profiles and physiological properties of mature Sensory Neurons and are responsive to nociceptor agonists.
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Selective conversion of fibroblasts into peripheral Sensory Neurons
Nature neuroscience, 2014Co-Authors: Joel W Blanchard, Kevin T Eade, Attila Szűcs, Valentina Lo Sardo, Rachel K Tsunemoto, Daniel Williams, Pietro Paolo Sanna, Kristin K BaldwinAbstract:Humans and mice detect pain, itch, temperature, pressure, stretch and limb position via signaling from peripheral Sensory Neurons. These Neurons are divided into three functional classes (nociceptors/pruritoceptors, mechanoreceptors and proprioceptors) that are distinguished by their selective expression of TrkA, TrkB or TrkC receptors, respectively. We found that transiently coexpressing Brn3a with either Ngn1 or Ngn2 selectively reprogrammed human and mouse fibroblasts to acquire key properties of these three classes of Sensory Neurons. These induced Sensory Neurons (iSNs) were electrically active, exhibited distinct Sensory neuron morphologies and matched the characteristic gene expression patterns of endogenous Sensory Neurons, including selective expression of Trk receptors. In addition, we found that calcium-imaging assays could identify subsets of iSNs that selectively responded to diverse ligands known to activate itch- and pain-sensing Neurons. These results offer a simple and rapid means for producing genetically diverse human Sensory Neurons suitable for drug screening and mechanistic studies.
Frédérique Scamps - One of the best experts on this subject based on the ideXlab platform.
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Morphology and nanomechanics of mice Sensory Neurons following peripheral nerve injury
2014Co-Authors: Marta Martin, Vivien Szabo, Thierry Cloitre, Csilla Gergely, Wafa Benzina, Frédérique ScampsAbstract:Dorsal root ganglia (DRG) contain a variety of Sensory Neurons that transduce somatic stimuli. Following peripheral nerve injury, Sensory Neurons have to adapt to a new environment in order to successfully promote their axonal elongation (regenerative growth mode). Unsuccessful regeneration leads to post-traumatic neuropathies, such ataxia and pain-related behavior, which are often chronic and mostly resistant to current treatments. Therefore understanding the cellular and molecular mechanisms leading to improved neurite re-growth is a major step to propose new therapies for nerve repair. In this work, we use differential interference contrast microscopy (DIC), fluorescence microscopy and atomic force microscopy (AFM) to study the morphological and nanomechanical properties of mice DRG Sensory Neurons in regenerative growth mode. DIC results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar Sensory Neurons but promoted the appearance of longer and larger neurites and growth cones. Our AFM data indicate that conditioned Neurons are characterized by softer growth cones and cell bodies, compared to control Neurons. As cell elasticity is related mainly to the intrinsic properties of the cell membrane and cytoskeleton structures such as microtubules and actin fibers, the increase of the cell membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins. Furthermore, in order to evidence structural differences between conditioned and control somas and growth cones, we use immunocytochemistry to localize actin (anti-actin antibody) and neuronal microtubules (anti-βIII-tubulin).
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Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury
PLoS ONE, 2013Co-Authors: Marta Martin, Frédérique Scamps, Olivier Lucas, Ouafa Benzina, Vivien Szabo, Thierry Cloitre, Attila Gergely Vegh, Csilla GergelyAbstract:A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of Sensory Neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar Sensory Neurons from mice dorsal root ganglia Sensory Neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live Neurons, we investigated whether membrane mechanical properties of growth cones of axotomized Neurons were modified following sciatic nerve injury. Our data revealed that Neurons having a regenerative growth were characterized by softer growth cones, compared to control Neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins.
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KCC3-dependent chloride extrusion in adult Sensory Neurons.
Molecular and Cellular Neuroscience, 2012Co-Authors: Olivier Lucas, Cécile Hilaire, Eric Delpire, Frédérique ScampsAbstract:The cation-Cl(-) cotransporters participate to neuronal Cl(-) balance and are responsible for the post-natal Cl(-) switch in central Neurons. In the adult peripheral nervous system, it is not well established whether a Cl(-) transition occurs during maturation. We investigated the contribution of cation-Cl(-) cotransporters in the Cl(-) handling of Sensory Neurons derived from the dorsal root ganglia (DRG) of neonatal mice (postnatal days 1-6) and adult mice. Gramicidin-perforated patch-clamp recordings in wild-type Neurons revealed that Cl(-) accumulated to very high values in P1-6 Sensory Neurons and decreased in adulthood. In post-natal Sensory Neurons, quantitative RT-PCR showed that NKCC1, KCC1 and KCC3 had a higher transcript expression level compared to KCC2 and KCC4. NKCC1 was the main cation-Cl(-) cotransporter controlling Cl(-) accumulation at this developmental stage. In adulthood, the KCC3 transcript was produced in larger amounts than the other cation-Cl(-) cotransporter transcripts and RT-PCR shows larger expression of the shorter KCC3a isoform in adult DRG. Pharmacological inhibitors of cation-Cl(-) cotransporters and the use of KCC3(-/-) mice demonstrated that NKCC1 sustained Cl(-) accumulation in the majority of adult Sensory Neurons while KCC3 contributed to Cl(-) extrusion in a subset of these Neurons. Beta-galactosidase detection in adult KCC3(-/-) DRG showed that KCC3 transcripts were present in all adult Sensory Neurons suggesting a KCC3 isoform specific regulation of Cl(-) handling. The contribution of KCC3 to Cl(-) extrusion in a subset of Sensory Neurons indicates that KCC3 could play a major role in GABAergic/glycinergic transmission.
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Calcium dependence of axotomized Sensory Neurons excitability.
Neuroscience Letters, 2005Co-Authors: Cécile Hilaire, Perrine Inquimbert, Mohammed Al-jumaily, Denis Greuet, Jean Valmier, Frédérique ScampsAbstract:Hyperexcitability of axotomized dorsal root ganglion Neurons is thought to play a role in neuropathic pain. Numerous changes in ionic channels expression or current amplitude are reported after an axotomy, but to date no direct correlation between excitability of axotomized Sensory Neurons and ionic channels alteration has been provided. Following sciatic nerve injury, we examined, under whole-cell patch clamp recording, the effects of calcium homeostasis on the electrical activity of axotomized medium-sized Sensory Neurons isolated from lumbar dorsal root ganglia of adult mice. Axotomy induced an increase in excitability of medium Sensory Neurons among which 25% develop a propensity to fire repetitively. The condition necessary to get burst discharge in axotomized Neurons was the presence of a high intracellular Ca2+ buffer concentration. The main effect was to amplify the increase in threshold current and apparent input resistance induced by axotomy. These data supply evidence for a role of Ca2+-dependent mechanisms in the control of excitability of axotomized Sensory Neurons.
