Different effects of nerve growth factor on cultured sympathetic and sensory neurons

Long-term cultures of dissociated nodose ganglion (NG) and superior cervical ganglion (SCG) neurons from newborn rabbits were used to compare their response to nerve growth factor (7S NGF). SCG neurons required added NGF for their survival and a concentration of 1 μg/ml was found to be optimal. NG neurons, on the other hand, survived well for a long term without addition of NGF, but its application (1 μg/ml) was found to be effective in accelerating the growth of fibers (neurites) and neuronal somata. It is concluded that unlike SCG, NG neurons do not depend on exogenous NGF but may require an intrinsic trophic-like factor which may be contained in the serum of the medium, emanating from glial cells or by metabolic cooperation between neurons.     

神经生长因子对培养的大鼠背根神经节神经元P物质释放的调节作用(英文)

目的观察神经生长因子(nerve growth factor, NGF)对原代培养的背根神经节(dorsal root ganglion, DRG)神经元中P物质(substance P, SP)的基础释放量和辣椒素诱发释放量的调节效应。方法将15 天胚龄的Wistar大鼠DRG神经元培养于含有不同浓度NGF的DMEM/F12培养液中,不含NGF的培养液培养的神经元作为对照。72小时后,用RT-PCR检测神经元中SP mRNA和辣椒素受体(vanilloid receptor 1, VR1)mRNA的表达,用放射免疫分析(radioimmunoassay,RIA)法检测SP的基础释放量和辣椒素(100 nmol/L)刺激10 min后的诱发释放量。结果SPmRNA和VR1 mRNA在NGF孵育的标本中表达增加,并与孵育液中NGF的浓度呈剂量依赖关系。SP的基础释放量和辣椒素诱发释放量在NGF孵育的标本中均增加,而且诱发释放量与NGF的浓度呈剂量依赖关系。结论NGF使DRG神经元SP的基础释放量和诱发释放量增加,表明NGF能增加初级传入神经元感受伤害刺激的敏感性,该效应可能与SP和VR1的mRNA表达增加有关。     

神经生长因子对培养的大鼠背根神经节神经元P物质释放的调节作用

目的观察神经生长因子（nerve growth factor, NGF）对原代培养的背根神经节（dorsal root ganglion, DRG）神经元中P物质（substance P, SP）的基础释放量和辣椒素诱发释放量的调节效应。方法将15 天胚龄的Wistar大鼠DRG神经元培养于含有不同浓度NGF的DMEM/F12培养液中,不含NGF的培养液培养的神经元作为对照。72小时后,用RT-PCR检测神经元中SP mRNA和辣椒素受体（vanilloid receptor 1, VR1）mRNA的表达,用放射免疫分析（radioimmunoassay,RIA）法检测SP的基础释放量和辣椒素（100 nmol/L）刺激10 min后的诱发释放量。结果SPmRNA和VR1 mRNA在NGF孵育的标本中表达增加,并与孵育液中NGF的浓度呈剂量依赖关系。SP的基础释放量和辣椒素诱发释放量在NGF孵育的标本中均增加,而且诱发释放量与NGF的浓度呈剂量依赖关系。结论NGF使DRG神经元SP的基础释放量和诱发释放量增加,表明NGF能增加初级传入神经元感受伤害刺激的敏感性,该效应可能与SP和VR1的mRNA表达增加有关。     

神经生长因子对糖皮质激素诱导大鼠海马神经元凋亡的保护作用

目的探讨神经生长因子对糖皮质激素诱导的大鼠海马神经元凋亡的保护作用。方法体外分离原代培养18只新生Wister大鼠海马神经元,噻唑蓝法测定地塞米松诱导海马神经元凋亡的最低敏感剂量,观察不同质量浓度神经生长因子对地塞米松(0.10×10~(-6)mol/L)诱导海马神经元凋亡的保护作用。结果与阴性对照组相比,地塞米松Ⅰ组(10×10~(-6)mol/L)、Ⅱ组(1×10~(-6)mol/L)和Ⅲ组(0.10×10~(-6)mol/L)大鼠海马神经元活性均降低(P=0.000,0.000,0.000)。予不同质量浓度神经生长因子后,神经生长因子0.18 ng/ml组大鼠海马神经元活性低于阴性对照组(P=0.000)和阳性对照组(P=0.010),神经生长因子18 ng/ml组大鼠海马神经元活性高于阳性对照组(P=0.000)和神经生长因子0.18 ng/ml组(P=0.000)。结论糖皮质激素可以诱导体外培养的大鼠海马神经元凋亡,地塞米松0.10×10~(-6)mol/L是诱导海马神经元凋亡的最低敏感剂量,神经生长因子可以拮抗地塞米松诱导的大鼠海马神经元凋亡。     

Correlation between GAP43 and nerve growth factor receptors in rat sensory neurons

In mature rat sensory neurons, expression of the gene for the growth-associated protein, GAP43, was studied by in situ hybridization with a cDNA probe. Among neurons in normal lumbar dorsal root ganglia, labeling for GAP43 mRNA was heterogeneous, approximately one-half of the neurons being densely labeled. To characterize the latter population, individual neurons were examined in adjacent sections processed either for GAP43 hybridization or NGF-receptor radioautography. Virtually all neurons with high-affinity NGF binding sites had high basal levels of GAP43 mRNA and most GAP43-positive neurons bore NGF receptors. Another NGF-responsive population, sympathetic neurons in the superior cervical ganglion, also had high basal concentrations of GAP43 mRNA. Further co-localization studies in dorsal root ganglia were performed with immunohistochemistry for somatostatin and enzyme histochemistry for acid phosphatase. The latter 2 groups of sensory neurons have been previously shown to lack high-affinity receptors and were here shown to have low basal concentrations of GAP43 mRNA. From this and earlier studies, it can be assumed that substance P-immunoreactive neurons and strongly positive CGRP neurons synthesize GAP43 at high basal rate. One week following peripheral nerve transection, almost all neurons had high concentrations of GAP43 mRNA without correlation with NGF binding. Intrathecal infusion of NGF after the sciatic nerve was cut did not strongly influence this post-traumatic elevation in GAP mRNA. In normal dorsal root ganglia, neurons that have high-affinity NGF binding sites and are therefore potentially responsive to NGF also have high basal rates of synthesis of GAP43.(ABSTRACT TRUNCATED AT 250 WORDS)     

Complete recovery by nerve growth factor of neuropeptide content and function in capsaicin-impaired sensory neurons

In the present study the ability of nerve growth factor (NGF) to facilitate the recovery of peptidergic primary sensory C-fibers after an acute capsaicin treatment (50 mg/kg s.c.) was investigated in adult rats. NGF (4 μg 1 /day for 3 days) was injected into the plantar of one hind paw starting 24 h after the capsaicin treatment. Without NGF, there was a significant reduction of calcitonin gene-related peptide (CGRP) and substance P content of the paw skin and the sciatic nerve. CGRP and substance P levels were completely replenished in the NGF-treated paw skin and in the innervating sciatic nerve they even increased over control levels as determined 40 h after the last injection of NGF. CGRP levels also recovered in the contralateral paw and sciatic nerve, but no recovery was observed in other tissues such as the front paw, the auricle, or the urinary bladder. Mustard oil-induced neurogenic plasma extravasation, taken as a functional parameter for peptidergic primary sensory C-fibers, was significantly decreased after the capsaicin treatment and showed a complete recovery by NGF in the injected paw as well as in the contralateral paw skin. These results show that NGF not only was able to reverse the decrease of transmitter content caused by capsaicin but also restored the peripheral function of primary afferent neurons.     

Effects of nerve growth factor on TTX- and capsaicin-sensitivity in adult rat sensory neurons

We have investigated the effects of nerve growth factor (NGF, 2.5 ng/ml for 1–2 weeks) on enriched adult rat dorsal root ganglion (DRG) neurons maintained in cell culture in defined media. Whole-cell recordings in cells cultured in the absence and presence of NGF revealed no significant difference in resting membrane potential and input resistance. However, the threshold for spike generation was significantly lower in untreated cells than in treated cells; −25 ± 1.1mV vs−19 ± 2.2mV, respectively. The sensitivity of the Na⁺ spike to tetrodotoxin (TTX, 1 μM) was different in cells cultured in the absence or presence of NGF. For example, spikes were abolished by TTX in 100% of untreated cells, while in NGF-treated cells the spike was abolished in only 41% of the neurons. Chemosensitivity of DRG neurons was also different in the absence and presence of NGF. For example, the percent of neurons in which a current activated by 8-methyl-N-vanillyl-6-nonenamide (capsaicin, 500 nM) was detected, increased from 18% in untreated cells to 55% in NGF-treated cells. NGF did not influence the number of cells surviving. The results indicate that NGF can regulate TTX and capsaicin sensitivity in these adult rat sensory neurons. Our experimental protocol indicates that this effect is not mediated by a factor in the serum or released from non-neuronal cells.     

Protective effect of nerve growth factor against glutamate-induced neurotoxicity in cultured cortical neurons

The effect of recombinant human nerve growth factor (hNGF) and mouse NGF on cultured rat cortical neurons was examined. The DNA fragment coding the human NGF gene was isolated and inserted downstream from the SV40 promoter in a plasmid containing the dihydrofolate reductase cDNA, and this plasmid was introduced into Chinese hamster ovary (CHO) cells to establish cells producing recombinant hNGF. The recombinant hNGF protein secreted by CHO cells was confirmed to be biologically active in an assay using PC12 cells. Brief exposure of cortical cells to glutamate followed by incubation with glutamate-free medium reduced cell viability by 60–70% when compared with the control culture. Simultaneous addition of recombinant hNGF or mouse NGF to rat cortical cultures with glutamate did not affect this reduction of cell viability. However, 24 h pretreatment of rat cortical cultures with recombinant hNGF or mouse NGF resulted in a significant reduction of glutamate-induced neuronal damage. Mouse NGF also protected cortical neurons against N-methyl-d-aspartate (NMDA)- and kainate-induced neuronal damage. These findings suggest that NGF can protect cortical neurons against glutamate-induced neurotoxicity.     

Effects of nerve growth factor on the survival of primary cultured adult and aged mouse sensory neurons

This study investigated the effects of exogenous nerve growth factor (NGF) on the survival and differentiation in primary culture of sensory neurons isolated from adult (6 months) and aged (2 years) mice. For neurons prepared from adult mice, a concentration effect was evident during a 2 week culture period: Neuronal counts in cultures supplemented with 25 and 50 ng/ml NGF did not differ significantly from those of control cultures without exogenous NGF or those with anti-NGF included in the culture medium, whereas cultures supplemented with either 100 or 200 ng/ml NGF contained higher numbers of neurons throughout the culture period. Cultures prepared from aged mice contained less neurons than those from adult mice, although those supplemented with 100 ng/ml NGF retained higher neuronal numbers than cultures from aged mice which did not receive exogenous NGF. Neuronal diameters were measured to investigate whether specific subpopulations of neurons were more dependent on NGF; the results indicate that neurons of a medium-larger diameter were more prevalent than cells with a smaller diameter following NGF administration. A shape index was calculated for each culture regimen; with longer culture periods a higher proportion of spindle-shaped neurons was observed. © 1993 Wiley-Liss, Inc.     

Immunohistochemical detection of glutamate in rat vagal sensory neurons

Vagal primary afferent neurons have their cell bodies located in the nodose (inferior) and jugular (superior) vagal ganglia and send terminals into the nucleus tractus solitarii (NTS) which lies in the dorsomedial medulla. The presence of glutamate (Glu)-containing neurons in the rat nodose ganglion was investigated using immunohistochemistry. Glu-immunoreactivity on nodose sections was found in neuronal perikarya and nerve fibers, but not in non-neuronal elements such as Schwann cells and satellite cells. Both immunoreactive and non-immunoreactive ganglion cells were observed. The immunoreactive ganglion cells amounted to about 60% of the nodose population. No specific intraganglionic localization was observed for the non-immunoreactive cells. Immunoreactive perikarya were slightly smaller than the non-immunoreactive ones, but no relationship was found between size and staining intensities of immunoreactive neurons. The present data indicate that immunodetectable Glu is present in a large population of vagal afferent neurons. They therefore add to a growing body of evidence suggesting that Glu may be the main neurotransmitter released by vagal afferent terminals within the nucleus tractus solitarii.     

Substance P post-synaptically potentiates glutamate-induced currents in dorsal vagal neurons

We examined the post-synaptic actions of glutamate, N-methyl-d-aspartate (NMDA) and substance P on dorsal vagal neurons, using the patch-clamp technique on brainstem slices of young rats. The vagal neurons were identified electrically and histologically. All vagal neurons responded to glutamate and NDMA and about 30% to substance P, with dose-dependent inward currents. The glutamate-induced currents were blocked partially by either CPP (3((R)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid) or CNQX (6-cyano-7-nitro-quinoxaline-2,3-dione), indicating that these currents resulted from the activation of at least two types of glutamate receptors: NMDA receptors and AMPA/kainate receptors. The NK1 receptor-selective antagonist, RP67580, blocked substance P-induced currents, suggesting that NK1 receptors do coexist with NMDA receptors and AMPA/Kainate receptors. Substance P potentiated the effects of glutamate. This potentiation lasted 10–20 min and was blocked by CPP and by RP67580, but not by CNQX, demonstrating that the increase in glutamate-induced currents resulted from the interaction between NK1 receptors and NMDA channels. These results provided the first evidence that the receptors for substance P and glutamate coexist on dorsal vagal neurons and interact with each other to modulate visceral efferent functions.     

Inhibition of axonal growth from sensory neurons by excess nerve growth factor

Fifteen-day embryonic rat dorsal root ganglion (DRG) neurons were exposed to 1 to 200 ng/ml nerve growth factor (NFG). Maximal neurite outgrowth was obtained with 10 to 20 ng/ml. Neurite outgrowth was reduced to 89% of maximal by increasing NGF to 50 ng/ml, to 66% by 100 ng/ml, and to 18% by 200 ng/ml NGF. Identical effects were seen with mouse 2.5S NGF and recombinant human NGF. Neuron cell counts demonstrated that significant cell death did not occur. In time course experiments, significant inhibition, compared with control, began within 1 hour of adding 200 ng/ml and 3 hours of adding 50 ng/ml NGF. The inhibitory effect of NGF on neurite outgrowth was reversed within 3 hours when DRG were incubated with 5 ng/ml NGF after treatment with 50 or 200 ng/ml NGF medium for 12 hours. The inhibition demonstrated for neurons did not occur in PC12 cells; axonal growth was not inhibited by up to 1,000 ng/ml NGF. Excess brain-derived neurotrophic factor or neurotrophin-3 did not inhibit neurite outgrowth. We conclude that high concentrations of NGF produces specific and reversible arrest of neurite outgrowth from sensory neurons. This observation has important clinical implications, because these inhibitory concentrations have been exceeded when NGF has been administered into the central nervous system of humans and animals.     

Effects of nerve growth factor on the survival and synaptic function of Ia sensory neurons axotomized in neonatal rats

Sensory neurons with small diameters (A delta and C cells) are known to be responsive to exogenous NGF even at postnatal stages. We have examined whether large Group Ia sensory neurons (A alpha cells) arising from muscle spindles are also responsive to NGF in neonatal rats. For this purpose, monosynaptic excitatory postsynaptic potentials (EPSPs) were evoked in spinal motoneurons by Group Ia muscle afferent volleys. When a muscle nerve was crushed on the day after birth, the monosynaptic EPSPs elicited by afferent volleys from the muscle were depressed within several weeks. This synaptic depression was partially reversed by daily treatment with NGF. NGF treatment also enhanced the EPSPs evoked by stimulation of intact muscle nerves, but this effect was less marked than that on the EPSPs produced by stimulation of the previously crushed muscle nerve. Exogenous NGF was effective for the EPSPs when the treatment began on the day after birth but not when the treatment began 4 d after birth. Following crush of a muscle nerve on the day after birth, about 45% of the sensory neurons derived from the muscle were lost. The cell death of small sensory neurons was prevented by daily treatment with NGF, whereas the NGF treatment was ineffective in preventing the cell death of large sensory neurons. The results indicate that Group Ia sensory neurons are responsive to NGF during early postnatal life.     

Time and dose dependencies of effects of nerve growth factor on sympathetic and sensory neurons in neonatal rats

Nerve growth factor (NGF) plays a role in the development of several components of the sympathetic and sensory nervous systems. The objectives of this study were to examine the time and dose dependencies of some of the well known effects of NGF on sympathetic ganglia and to examine qualitatively and quantitatively the recently described effects on sensory ganglia of neonatal rats. Single doses of NGF as low as 0.1 mg/kg produce increases in tyrosine hydroxylase (TOH) activity in superior cervical ganglia (SCG), and doses of 3 mg/kg produce maximal effects. Larger doses and longer treatments are required to see increases in protein content of the SCG. Larger doses are also required to affect TOH activity in the adrenal gland. Increases in TOH activity in SCG can be observed within 18 h of injection. Chronic NGF treatment for three weeks produces no change in blood pressure or heart rate in neonatal rats. Chronic administration of NGF (1 or 3 mg/kg/day) results in dose-related increases in the protein content of dorsal root ganglia (DRG). The increase in protein content of the DRG was associated with an increase in the diameter of smaller neurons (those<30 μm in diameter), but NGF caused no change in the number of neurons.     

Substance P in the vagal sensory ganglia: Localization in cell bodies and pericellular arborizations

The distribution of Substance P-like immunoreactivity in the jugular and nodose ganglia of rabbits and pigeons has been studied using immunocytochemical staining techniques. Substance P-like immunoreactivity is localized to neuronal cell bodies and processes in the jugular and nodose ganglia, and to pericellular fiber plexi in the nodose ganglia of both species. The numbers and sizes of cells which exhibited Substance P-like immunoreactivity in each ganglion were determined using quantitative morphometric techniques. The distribution of Substance P-like immunoreactivity in the rabbit and pigeon vagal sensory ganglia is characterized by several general features. In most of the ganglia, immunoreactive neurons factor into discrete types which can be distinguished from one another, and from non-immunoreactive neurons, by size. In addition, immunoreactive nodose and jugular ganglion cells, respectively, are distinguishable on the basis of size. Finally, a considerably higher percentage of immunoreactive neurons is found in the jugular ganglion than in the nodose ganglion. Substance P-like immunoreactivity was also seen in pericellular fiber plexi which encircle individual neurons in the nodose ganglion of rabbits and pigeons. These plexi are composed of varicose fibers which appear to terminate as boutons on the surfaces of the cells which they encircle. The distribution of Substance P-like immunoreactivity within the vagal sensory ganglia is discussed with respect to the possible peripheral targets and functions of Substance P-containing vagal afferents. Our findings suggest that Substance P-containing vagal sensory neurons are involved in a variety of visceral and somatic afferent functions.     

The effect of endoneurial nerve growth factor on calcitonin gene-related peptide expression in primary sensory neurons

Recent findings indicate that calcitonin gene-related peptide (CGRP) is involved in neuropathic pain, this peptide being up-regulated in a small population of large- and medium-sized primary sensory neurons after peripheral nerve injury. In adult animals, the expression of CGRP is regulated by nerve growth factor (NGF). After nerve injury, NGF is up-regulated at the injury site for several weeks, and this up-regulation contributes to the onset of neuropathic pain. Using immunohistochemistry, we investigated the time course of the effect of an endoneurial injection of NGF on the expression of CGRP in primary sensory neurons. NGF increased the percentage of medium- to large-sized DRG neuron profiles expressing CGRP, did not modify the percentage of small-sized neurons expressing CGRP, and increased CGRP expression in the laminae III and IV of the dorsal horn. The effects of NGF were evident as soon as 1 day after endoneurial injection, and lasted for 5 days. Ten days after the injection of NGF, the patterns of CGRP expression in the DRG were normal, whereas a slight decrease in CGRP content was observed in the dorsal horn. The injection of vehicle did not produce any change on CGRP expression in primary sensory neurons. These results suggest that endoneurial NGF is responsible for the increase in CGRP expression in some large-sized neurons and their central processes observed after nerve injury in animal models of neuropathic pain. Our findings contribute to the understanding of the role of NGF in neuropathic pain.     

Osteocalcin-immunoreactive neurons in the vagal and glossopharyngeal sensory ganglia of the rat

Immunohistochemistry for osteocalcin (OC) was performed on the rat vagal and glossopharyngeal sensory ganglia. OC-immunoreactive (IR) neurons were detected in the jugular (10%), petrosal (11%) and nodose ganglia (6%). The cell size analysis demonstrated that OC-IR neurons were predominantly small to medium-sized in the jugular ganglion (mean+/-S.D.=356.3+/-192.2 microm(2), range=86.5-831.5 microm(2)). On the other hand, such neurons were medium-sized to large in the petrosal (mean+/-S.D.=725.6+/-280.7 microm(2), range=124.7-1540.4 microm(2)) and nodose ganglia (mean+/-S.D.=857.5+/-330.2 microm(2), range=367.1-1608.0 microm(2)). In the circumvallate papilla, OC-IR nerve fibers were located in the vicinity of taste buds. Some taste bud cells were also immunoreactive for the calcium-binding protein (CaBP). In the carotid body, however, OC-IR nerve fibers could not be detected. Retrograde tracing with fluorogold revealed that OC-IR nerve fibers in the circumvallate papilla mainly originated from the petrosal ganglion. These findings may suggest that OC-IR petrosal neurons have chemoreceptive function in the tongue.     

人NGF促进感觉神经生长和诱导SP释放实验研究

目的采用体外模型对比研究观察,评估人痛性椎间盘细胞外基质对小鼠背根神经节神经轴突生长所产生的促进作用和神经肽（sP）的诱导作用。方法通过获取椎间盘源性下腰痛患者的椎间盘组织（退变组）,以及正常人腰椎间盘组织（正常组）提取细胞基质,对小鼠背根神经节神经元（DRG）进行培养,通过形态学观察神经元轴突生长和酶联免疫吸附法（ELISA）检测SP含量。结果实验组神经生长因子（NGF）浓度显著高于正常组;实验组神经元轴突平均长度为（134．17±2．21）μm,明显高于正常组的（121．28±4．10）μm,二者相比有明显差异性（P〈0．05）。在退变人椎间盘组织培养液中SP物质比率明显高于正常组（P〈0．001）,二者具有显著性差异。结论人退变椎间盘细胞外基质中高表达的NGF能促进感觉神经轴突的生长以及诱导和疼痛相关神经肽的释放。