首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
    
《Developmental neurobiology》2017,77(9):1038-1056
Receptor for activated C kinase 1 (RACK1) is a multifunctional ribosomal scaffolding protein that can interact with multiple signaling molecules concurrently through its seven WD40 repeats. We recently found that RACK1 is localized to mammalian growth cones, prompting an investigation into its role during neural development. Here, we show for the first time that RACK1 localizes to point contacts within mouse cortical growth cones. Point contacts are adhesion sites that link the actin network within growth cones to the extracellular matrix, and are necessary for appropriate axon guidance. Our experiments show that RACK1 is necessary for point contact formation. Brain‐derived neurotrophic factor (BDNF) stimulates an increase in point contact density, which was eliminated by RACK1 shRNA or overexpression of a nonphosphorylatable mutant form of RACK1. We also found that axonal growth requires both RACK1 expression and phosphorylation. We have previously shown that the local translation of β‐actin mRNA within growth cones is necessary for appropriate axon guidance and is dependent on RACK1. Thus, we examined the location of members of the local translation complex relative to point contacts. Indeed, both β‐actin mRNA and RACK1 colocalize with point contacts, and this colocalization increases following BDNF stimulation. This implies the novel finding that local translation is regulated at point contacts. Taken together, these data suggest that point contacts are a targeted site of local translation within growth cones, and RACK1 is a critical member of the point contact complex and necessary for appropriate neural development. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1038–1056, 2017  相似文献   

2.
Spontaneous and potassium-induced acetylcholine release from embryonic (E12 and E18) chick dorsal root ganglia explants at 3 and 7 days in culture was investigated using a chemiluminescent procedure. A basal release ranging from 2.4 to 13.8 pm/ganglion/5 min was detected. Potassium application always induced a significant increase over the basal release. The acetylcholine levels measured in E12 explants were 6.3 and 38.4 pm/ganglion/5 min at 3 and 7 days in culture, respectively, while in E18 explant cultures they were 10.7 and 15.5 pm/ganglion/5 min. In experiments performed in the absence of extracellular Ca2+ ions, acetylcholine release, both basal and potassium-induced, was abolished and it was reduced by cholinergic antagonists. A morphometric analysis of explant fibre length suggested that acetylcholine release was directly correlated to neurite extension. Moreover, treatment of E12 dorsal root ganglion-dissociated cell cultures with carbachol as cholinergic receptor agonist was shown to induce a higher neurite outgrowth compared with untreated cultures. The concomitant treatment with carbachol and the antagonists at muscarinic receptors atropine and at nicotinic receptors mecamylamine counteracted the increase in fibre outgrowth. Although the present data have not established whether acetylcholine is released by neurones or glial cells, these observations provide the first evidence of a regulated release of acetylcholine in dorsal root ganglia.  相似文献   

3.
4.
Semaphorin 3E/collapsin-5 inhibits growing retinal axons   总被引:2,自引:0,他引:2  
During development, the formation of neural networks is reflected by the oriented extension of neurites. Using retinal ganglion cells (RGCs) as a model, we identified the yet uncharacterized chick semaphorin Sema3E/collapsin-5 as a repulsive cue for outgrowing axons. Sema3E/collapsin-5 was highly regulated during retinal histogenesis, with peak expression during the period of intraretinal axon growth. Polymerase chain reaction analysis demonstrated Sema3E/collapsin-5 mRNA in retina layers, from which RGC axons are excluded. Neither isolated RGCs nor purified retinal Müller glia cells synthesized Sema3E/collapsin-5. Sema3E/collapsin-5 receptor sites were visualized by alkaline phosphatase fusion proteins in the axon-rich optic fiber layer. Time-lapse video recording of chick in vitro cultures revealed a growth cone collapsing activity of recombinant Sema3E/collapsin-5. This effect was specific for RGCs, since dorsal root ganglia (DRG) neurons of the peripheral nervous system were not affected. Comparison with Sema3A/collapsin-1 displayed a reciprocal specificity, because Sema3A/collapsin-1 hampered exclusively DRG but not RGC growth cones. The collapsing effect was mediated by low cGMP levels, but not cAMP, as revealed by a set of agonists. In summary, the data suggest a possible role of chick Sema3E/collapsin-5 in restricting growth of retinal ganglion cell axons to the optic fiber layer.  相似文献   

5.
6.
In co-culture of spinal cord and dorsal root ganglion (DRG) neurons, we studied at different terms of culturing postsynaptic currents in DRG neurons evoked by direct electrical stimulation of single spinal neurons using a voltage-clamp technique in the whole-cell configuration. According to the reversal potential and sensitivity to bicuculline, these currents were classified as inhibitory postsynaptic currents (IPSC) carried by Cl- ions through GABAA receptors. During neuronal development in dissociated co-culture, the amplitude of evoked IPSC and their time to peak significantly increased. The time to peak of spontaneous IPSC (sIPSC) in DRG neurons remained unchanged, while the frequency of these currents increased with increasing culturing time. It is concluded that under culturing conditions spinal neurons establish inhibitory synaptic contacts with the somata of DRG neurons, and the number of such functional contacts increases in the course of culturing. Our findings show that in dissociated co-culture the process of formation of inhibitory synapses on the axon terminals of primary afferent neurons is akin to that realized in vivo, but with dissimilar topography of distribution of such synapses.  相似文献   

7.
大电导的电压和 Ca2+ 激活的 K+ 通道 (BK 通道 ) 在哺乳动物的组织中广泛表达,起着多种多样的作用 . 目前只有少数组织中 BK 通道的性质被深入地研究,而且鲜见有失活的 BK 通道 (BKi) 的报道,尤其是在神经元中 . 发现在大鼠小直径的背根神经节 (DRG) 神经元中,普遍存在失活的 BK 通道 . 失活的 BK 电流成分是 Ca2+敏感的,可以被大电导的 BK 通道特异阻断剂 ChTX 所阻断,而且木瓜蛋白酶可以从胞外改变通道失活的特性 .  相似文献   

8.
Summary 1. Growth cones of cultured dorsal root ganglion neurons from mice were irradiated using a mercury lamp.2. The flux of particles of fast retrograde axoplasmic transport decreased promptly after light irradiation without a change in velocity.3. That of anterograde transport decreased as well, but with a significant latency. The decrease in the anterograde flux was attributed to decreased velocity of particles.4. Video-enhanced contrast microscopy of growth cones revealed transient swelling of growth cones and transient stagnation of particles in growth cones.5. The longer the neurite, the larger the latency of the change of the anterograde transport; peripheral information was calculated to be conveyed to the cell body at a speed of 6 µm/min.6. The mechanism of this information conveyance and the export of materials from the cell body are discussed.  相似文献   

9.
The effect of the alpha subunit of the 7S-NGF on the binding of beta-NGF to its two classes of sites on target cells has been studied. The presence of microM concentrations of alpha-NGF causes the displacement of 125I-beta-NGF from one class of sites on dissociated dorsal root ganglia neurons from stage E9 chicken embryos. At 0.1 nM 125I-beta-NGF, increasing alpha-NGF concentrations produce a monotonic displacement curve with half-maximal displacement occurring at 10 microM alpha-NGF. The affinity and number of sites of the 125I-beta-NGF displaced by alpha-NGF are similar to those of beta-NGF that binds to the higher affinity (site I) receptors. The binding to the lower affinity class of sites (site II) is not affected by concentrations of alpha-NGF up to 30 microM. This modulation of 125I-beta-NGF binding does not occur with equivalent concentrations of serum albumin. No detectable neuronal binding of 125I-alpha-NGF was found, suggesting that the mechanism does not involve direct competition for receptor sites. The dissociation constant for the alpha-beta complex is in the microM range, and formation of this complex in solution can thus compete with the process of 125I-beta-NGF binding to neurons. A model accounting for these observations includes binding of the alpha-beta complex to the lower affinity but not to the higher affinity sites. We conclude that there are differences in the specificity of the two classes of receptors.  相似文献   

10.
本文采用逆转录聚合酶链反应(RT-PCR)方法测定大鼠内毒素血症不同时期胸腰段背根神经节降钙素基因相关肽(CGRP)mRNA水平的改变,结合血浆CGRP水平的改变,以期全面了解大鼠内毒素血症不同时期CGRP释放与合成的变化。结果显示:注射内毒素(5mg/kg)后30min时,大鼠血浆CGRP开始增高,而背根神经节CGRPmRNA水平无明显变化;注射内毒素后3h时,血浆CGRP及背根神经节CGRPmRNA均明显增高.分别为142%和32%,8h时则进一步增高,分别为216%和85%。提示内毒素不仅刺激外周组织释放CGRP,而且还能通过某些机制激活背根神经节CGRPmRNA的转录,使CGRP合成增加,以作为CGRP大量释放的重要补充来源。  相似文献   

11.
Hingtgen CM 《生理学报》2008,60(5):581-583
Neurofibromatosis type 1 (NF1) is a common autosomal dominant disease characterized by formation of multiple benign and malignant tumors. People with this disorder also experience chronic pain, which can be disabling. Neurofibromin, the protein product of the Nfl gene, is a gnanosine triphosphatase activating protein (GAP) for p21Ras (Ras). Loss of Nfl results in an increase in activity of the Ras transduction cascade. Because of the growing evidence suggesting involvement of downstream components of the Ras transduction cascade in the sensitization of nociceptive sensory neurons, we examined the stimulus-evoked release of the neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP), from primary sensory neurons of mice with a mutation of the Nfl gene (NfI 1-). Measuring the levels of SP and CGRP by radioimmunoassay, we demonstrated that capsaicin-stimulated release of neuropep-tides is 3-5 folds higher in spinal cord slices from Nfl 1-mice than that from wildtype mouse tissue. In addition, the potassium- and capsaicin-stimulated release of CGRP from the culture of sensory neurons isolated from Nfl 1- mice was more than double that from the culture of wildtype neurons. Using patch-clamp electrophysiological techniques, we also examined the excitability of capsaicin-sensitive sensory neurons. It was found that the number of action potentials generated by the neurons from Nfl 1- mice, responsing to a ramp of depolarizing current, was more than three times of that generated by wildtype neurons. Consistent with that observation, neurons from Nfl 1- mice had lower firing thresholds, lower rheobase currents and shorter firing latencies compared with wildtype neurons. These data clearly demonstrate that GAPs, such as neurofihromin, can alter the excitability of nociceptive sensory neurons. The augmented response of sensory neurons with altered Ras signaling may explain the abnormal pain sensations experienced by people with NFI and suggests an important role of GAPs in the mechanism of sensory neuron sensitization.  相似文献   

12.
本实验将1%CB-HRP注入大鼠左侧腰4节段脊神经节(DRG)两天后,观察到同侧相应节段脊髓前角第Ⅷ层和Ⅸ层内有HRP标记胞体。电镜观察显示,在切断大鼠左侧L4和L5前根后5~7天,在相应节段的DRG内见到变性纤维或终末。上述结果提示,前角运动神经元可发出纤维经前根到DRG,及可能参与调节一级感觉信息的传入。  相似文献   

13.
14.
Polyclonal antibodies to ganglioside GM1 have been prepared and characterised by direct and competitive enzyme-linked immunoassay. An immunoglobulin fraction was prepared from a rabbit antisera showing high specificity and antibody titre for GM1 relative to the other major brain gangliosides. The anti-GM1 immunoglobulin fraction and B-cholera toxin specifically labelled neurons in primary cultures of embryonic chick dorsal root ganglia and there was a good correlation between the relative increase in binding of anti-GM1 immunoglobulin and B-cholera toxin following neuraminidase treatment of a variety of cell types. At antibody concentrations that show saturable binding to endogenous ganglioside in the neuronal membrane, the anti-GM1 immunoglobulin fraction did not interfere with the nerve growth factor (NGF)-mediated fibre outgrowth and neuronal survival as indexed by measurement of neurofilament protein levels. Similarly, at levels in excess of those shown to stimulate thymocyte proliferation, B-cholera toxin was also without effect. These data are not consistent with GM1 in the neuronal membrane functioning as a receptor molecule for NGF and/or other differentiation factors present in the tissue culture media.  相似文献   

15.
    
Progranulin haploinsufficiency is associated with frontotemporal dementia in humans. Deficiency of progranulin led to exaggerated inflammation and premature aging in mice. The role of progranulin in adaptations to nerve injury and neuropathic pain are still unknown. Here we found that progranulin is up-regulated after injury of the sciatic nerve in the mouse ipsilateral dorsal root ganglia and spinal cord, most prominently in the microglia surrounding injured motor neurons. Progranulin knockdown by continuous intrathecal spinal delivery of small interfering RNA after sciatic nerve injury intensified neuropathic pain-like behaviour and delayed the recovery of motor functions. Compared to wild-type mice, progranulin-deficient mice developed more intense nociceptive hypersensitivity after nerve injury. The differences escalated with aging. Knockdown of progranulin reduced the survival of dissociated primary neurons and neurite outgrowth, whereas addition of recombinant progranulin rescued primary dorsal root ganglia neurons from cell death induced by nerve growth factor withdrawal. Thus, up-regulation of progranulin after neuronal injury may reduce neuropathic pain and help motor function recovery, at least in part, by promoting survival of injured neurons and supporting regrowth. A deficiency in this mechanism may increase the risk for injury-associated chronic pain.  相似文献   

16.
Summary The influence of nerve growth factor (NGF) on Na currents of rat dorsal root ganglia (DRG) was studied in neurons obtained from newborns and cultured for 2–30 hr inserum-free defined medium (SFM). Cell survival for the period studied was 78–87% both with and without NGF. Na currents were detected in all cells cultured for 6–9 hr. They were also detected after 2 hr in culture in 21.5% of the cells cultured without NGF (–NGF cells), and in 91.5% of the cells cultured with NGF (+NGF cells). Current density of the -NGF cells was 2.3 and 2 pA/m2 after growth for 2 and 6–9 hr, respectively, compared to 3.0 and 3.9 pA/m2 for the +NGF cells. The +NGF cells were separated into fast (F), Intermediate (I) and slow (S) cells, based on the Na current they expressed, while -NGF cells were all of theI type.F, I andS currents differed in their voltage-dependent inactivation (Vh 50=–79, –28 and –20 mV), kinetics of inactivation (tau h =0.55, 1.3 and 7.75 msec), and TTX sensitivity (K i=60, 550 and 1100nm). All currents were depressed by [Ca] o with aKd Ca of 22, 17 and 8mm forF, I andS currents, respectively. Current density ofF andS currents was 5.5 and 5 pA/m2 for theI current. The concentration-dependent curve ofI currentvs. TTX indicated thatI current has two sites: one withF-like and another withS-likeK i for TTX. Hybridization ofF andS currents yieldI-like currents. Thus, the major effect of NGF on Na currents in SFM is the accleration of Na current acquisition and diversity, reflected in an increase of either theS orF type in a cell.  相似文献   

17.
Summary A new type of collagen surface for use with cultures of peripheral nervous system cells is described. Collagen is derivatized to plastic culture dishes by a cross-linking reagent, 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide-metho-p-toluenesulfonate (carbodiimide), to form a uniform and durable surface for cell attachment and growth that allows dry storage, long-term culture, and improved microscopy. Surfaces of collagen derivatized to plastic were compared to surfaces of adsorbed or ammonia-polymerized collagen in terms of collagen binding and detachment, growth by dorsal root ganglion cells, and electron microscopy appearances. Derivatized collagen surfaces retained more collagen and showed much less evidence of degradation and cellular damage over periods of many weeks than did conventional adsorbed surfaces. Long-term survival of cells on derivatized collagen was far superior to that on the other surfaces, with almost 90% of cultures still viable after 10 wk. Transmission electron microscopy showed an organized layer of single fibrils that supported cell growth well, and scanning electron microscopy demonstrated an increased uniformity of derivatized collagen surfaces compared to ammoniated collagen surfaces. Applications for this improved substrate surface are discussed. This work was supported by the Leopold Schepp Foundation, the Dysautonomia Foundation, National Institutes of Health Grants NS14768 and NS11237, and Institutional Core Grant HD06276.  相似文献   

18.
19.
    
Diabetic neuropathy is a frequent complication of diabetes mellitus, for which no adequate clinical treatment is currently available. One of the main reasons for the absence of effective treatment of this disease is that information on how metabolic, vascular, and other abnormalities involved in the pathogenesis of diabetic neuropathy lead to dysfunction of nerve cells and pathways remains insufficient. Recent studies demonstrated that substantial abnormalities of calcium homeostasis in input neurons of the somatosensory nociceptive system are associated with many symptoms of diabetic neuropathy. Although proof of the causal linkage between calcium abnormalities and neuropathic complications is not conclusive, current research in neuroscience mostly indicates that such a linkage exists. Practically all known modifications of synaptic transmission in both central and peripheral nervous systems result from calcium-dependent modifications of the molecular players involved in this transmission. This is why the main goal of our review is to analyze in detail the fundamental cellular and molecular calcium-regulating mechanisms that are deteriorated in diabetes. As an important end-point of the proposed review, the capability of a widely used calcium channel blocker, nimodipine, to correct cytosolic and endoplasmic reticulum calcium abnormalities in neurons of the dorsal root ganglia and spinal dorsal horn and possible curative value of this agent in diabetic neuropathy are discussed.Neirofiziologiya/Neurophysiology, Vol. 36, No. 4, pp. 348–353, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.  相似文献   

20.
In co-cultured dorsal root ganglion (DRG) neurons and spinal cord neurons from newborn rats, using a voltage-clamp technique in the whole-cell configuration enabled us to observe in DRG neurons the effects evoked by extracellular local electrical stimulation of cells corresponding to spinal cord neurons in their morphological characteristics. Such stimulation caused the appearance of postsynaptic currents (PSC) in DRG neurons in 9% of the cases. The mean delay of these currents (measured from the stimulus leading edge) was 4.7 ± 0.29 msec, the mean time to peak was 2.6 ± 0.77 msec, and the decay time constant = 14.5 ± 1.04 msec. The reversal potential of evoked PSC (ePSC) was close to the equilibrium potential for chloride ions estimated by the Nernst equation. Application of 20 M bicuculline induced practically complete and reversible ePSC block. The conclusion was drawn that these currents arise due to activation of the chloride channels operated by GABA receptors and, hence, represent an inhibitory PSC. Thus, one may deem it proved that spinal cord neurons can establish functional inhibitory synapses with DRG neurons.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号