The distribution and origin of VIP in the spinal cord of six mammalian species

The distribution of VIP-immunoreactivity was studied in the spinal cord and dorsal root ganglia of 6 mammalian species. Immunoreactive fibres and cell bodies were most apparent in the dorsal horn, dorsolateral funiculus, intermediolateral cell columns and the area around the central canal. The distribution of VIP immunoreactivity was similar in all species studied, mouse, rat, guinea pig, cat, horse and the marmoset monkey. There were fewer VIP fibres in the dorsal horn of cervical and thoracic segments than in lumbosacral segments. Using radioimmunoassay this gradient increase was quantitatively most marked in the sacral spinal cord of the cat. In dorsal root ganglia few nerve cell bodies but numerous fibres were present. A dual origin for VIP in the spinal cord is suggested: (A) Extrinsic, from dorsal root afferent fibres since immunoreactivity was decreased in dorsally rhizotomized animals (cats and rats) and in capsaicin pretreated rats (microinjection of dorsal root ganglia). (B) From local cell bodies intrinsic to the spinal cord which became visible after colchicine pretreatment of rats.     

Differential Changes in Neuronal Excitability in the Spinal Dorsal Horn After Spinal Nerve Ligation in Rats

Previous studies demonstrated that peripheral nerve injury induced excessive neuronal response and glial activation in the spinal cord dorsal horn, and such change has been proposed to reflect the development and maintenance of neuropathic pain states. The aim of this study was to examine neuronal excitability and glial activation in the spinal dorsal horn after peripheral nerve injury. We examined noxious heat stimulation-induced c-Fos protein-like immunoreactivity (Fos-LI) neuron profiles in fourth-to-sixth lumbar (L4–L6) level spinal dorsal horn neurons after fifth lumbar spinal nerve ligation (L5 SNL). Immunofluorescence labeling of OX-42 and GFAP was also performed in histological sections of the spinal cord. A significant increase in the number of Fos-LI neuron profiles in the spinal dorsal horn at the L4 level was found at 3 days after SNL, but returned to a level similar to that in sham-operated controls by 14 days after injury. As expected, a decrease in the number of Fos-LI neuron profiles in the spinal dorsal horn at the L5 level was found at 3 days after SNL. However, these profiles had reappeared in large numbers by 14 and 21 days after injury. Immunofluorescence labeling of OX-42 and GFAP indicated sequential activation of microglia and astrocytes in the spinal dorsal horn. We conclude that nerve injury causes differential changes in neuronal excitability in the spinal dorsal horn, which may coincide with glial activation. These changes may play a substantial role in the pathogenesis of neuropathic pain after peripheral nerve injury.     

Spinal Autofluorescent Flavoprotein Imaging in a Rat Model of Nerve Injury-Induced Pain and the Effect of Spinal Cord Stimulation

Nerve injury may cause neuropathic pain, which involves hyperexcitability of spinal dorsal horn neurons. The mechanisms of action of spinal cord stimulation (SCS), an established treatment for intractable neuropathic pain, are only partially understood. We used Autofluorescent Flavoprotein Imaging (AFI) to study changes in spinal dorsal horn metabolic activity. In the Seltzer model of nerve-injury induced pain, hypersensitivity was confirmed using the von Frey and hotplate test. 14 Days after nerve-injury, rats were anesthetized, a bipolar electrode was placed around the affected sciatic nerve and the spinal cord was exposed by a laminectomy at T13. AFI recordings were obtained in neuropathic rats and a control group of naïve rats following 10 seconds of electrical stimulation of the sciatic nerve at C-fiber strength, or following non-noxious palpation. Neuropathic rats were then treated with 30 minutes of SCS or sham stimulation and AFI recordings were obtained for up to 60 minutes after cessation of SCS/sham. Although AFI responses to noxious electrical stimulation were similar in neuropathic and naïve rats, only neuropathic rats demonstrated an AFI-response to palpation. Secondly, an immediate, short-lasting, but strong reduction in AFI intensity and area of excitation occurred following SCS, but not following sham stimulation. Our data confirm that AFI can be used to directly visualize changes in spinal metabolic activity following nerve injury and they imply that SCS acts through rapid modulation of nociceptive processing at the spinal level.     

Effects of Peripheral Axotomy on Cholecystokinin Neurotransmission in the Rat Spinal Cord

Abstract : Because cholecystokinin (CCK) acts as a "functional" endogenous opioid antagonist, it has been proposed that changes in central CCKergic neurotransmission might account for the relative resistance of neuropathic pain to the analgesic action of morphine. This hypothesis was addressed by measuring CCK-related parameters 2 weeks after unilateral sciatic nerve section in rats. As expected, significant decreases (-25-38%) in the tissue concentrations and in vitro release of both substance P and calcitonin gene-related peptide were noted in the dorsal quadrant of the lumbar spinal cord on the lesioned side. In contrast, the tissue levels and in vitro release of CCK were unchanged in the same area in lesioned rats. Measurements in dorsal root ganglia at L4-L6 levels revealed no significant changes in proCCK mRNA after the lesion. However, sciatic nerve section was associated with a marked ipsilateral increase in both CCK-B receptor mRNA levels in these ganglia (+70%) and the autoradiographic labeling of CCK-B receptors by [³H]pBC 264 (+160%) in the superficial layers of the lumbar dorsal horn. Up-regulation of CCK-B receptors rather than CCK synthesis and release probably contributes to increased spinal CCKergic neurotransmission in neuropathic pain.     

坐骨神经结扎后大鼠背根神经节和脊髓CGRP表达的变化

目的研究大鼠坐骨神经结扎后降钙素基因相关肽(calcitoningene-relatedpeptide,CGRP)表达变化。方法SD大鼠随机分为假手术对照组和坐骨神经结扎组,实验组结扎后分别存活1、3、5、7、14、21和28d(n=8),免疫荧光(双标法)和免疫组织化学(SABC法)观察术后不同时间点CGRP和NGF在坐骨神经、背根神经节(dorsalrootganglion,DRG)和脊髓的表达变化,Westernblot结合图像分析技术对不同时间的变化进行定量测定。结果术后1d结扎远端坐骨神经内NGF大量堆积,持续到28d仍高于正常。结扎后7dDRG内CGRP阳性细胞百分率减少,持续到28d仍低于正常;结扎后14d脊髓后角CGRP下降,28d仍低于正常,各时间点脊髓前角CGRP表达未见明显变化。结论神经结扎可导致DRG和脊髓后角的CGRP表达下调,可能与靶源性的NGF来源减少有关。     

Autotomy and decreased spinal substance P following peripheral cryogenic nerve lesion.

Cryotherapy has been clinically applied to relieve pain by blocking peripheral nerve function. Clinically, analgesia has been successfully achieved but there is suggestion that permanent pain relief may be accompanied by extended motor and sensory deficits. This study was undertaken to determine the effect of a peripheral cryogenic nerve lesion, i.e., of the sciatic nerve, on behavioral effects and substance P content in the dorsal horn of the spinal cord. In rats, the right sciatic nerve was exposed and cryolesioned using one freeze-thaw-refreeze cycle. In an alternate group, the right sciatic nerve was cut and a 3-mm region was excised. Animals were allowed to recover 7 or 21 days during which their behavior was assessed. Autotomy, an animal's tendency to attack the nerve-injured affected limb, occurred in both the cryolesioned and sectioned groups. They were killed by transcardiac perfusion of fixative and segments L4-S1 were processed for immunocytochemistry. The SP-like immunoreactivity (SPLI) in the right and left dorsal horns was compared and quantitated using a microcomputer imaging device. We utilized a fully automated program to digitize and quantitate the staining of the substantia gelatinosa. There was no significant difference in SPLI in the dorsal horns of the sham-operated controls at either time period. At 7 days the sectioned group demonstrated a 40% decrease in SPLI and 76% decrease at 21 days. In the cryolesioned group, there was a 34% decrease at 7 days and by 21 days there was a 68% decrease in immunoreactivity on the operated side.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of aerobic exercise training on the age-related lipid peroxidation, Schwann cell apoptosis and ultrastructural changes in the sciatic nerve of rats

The potential role of exercise in preventing the age-related spontaneous peripheral neuropathy has not been studied. We examined the effects of long-term aerobic exercise training on lipid peroxidation, Schwann cell (SC) apoptosis and ultrastructural changes in the sciatic nerve of rats during aging. Three groups of 12-week old Wistar rats ran on a treadmill for 6, 9 and 12 months (exercise trained (ET) group, n=10 each) according to an exercise training program targeted at a speed of 22 m/min (at 7 degrees incline), 60 min/day, 6 days/week. Three corresponding groups of untrained rats were used as the controls (sedentary (SED) group). At the end of each period, sciatic nerve biopsies were performed, and processed for biochemical, immunohistochemical and ultrastructural analyses. The results showed that aging was associated with an increased level of nerve malondialdehyde (MDA, marker of lipid peroxidation) and a higher number of SC apoptosis in SED group. The SED group showed irregular nerve fibers with thin myelin sheaths and areas of myelin-axon detachment. However, the ET group had significantly diminished nerve lipid peroxidation and SC apoptosis. In the ET group, nerve fibers had a thick myelin sheath with frequent folding. These findings suggest that aerobic exercise training protects peripheral nerves by attenuating oxidative reactions, and preserving SCs and myelin sheath from pathologic changes, which occur during normal aging.     

Immunohistochemical study on the distribution of neuronal nitric oxide synthase-immunoreactive neurons in the spinal cord of aged rat

Summary Despite in vivo studies suggesting an important function for nitric oxide (NO) in the spinal cord in the transmission of pain signals, sympathetic nerve activity and presumably other spinal functions, changes of neuronal NO synthase (nNOS)-containing neurons with aging in the spinal cord has not been investigated. In the present study, we demonstrated for the first time that the number of nNOS-immunoreactive neurons was significantly decreased in the central autonomic nucleus and the superficial dorsal horn of spinal cord in aged rats. Morphologically, the number and length of dendritic branches also seemed to be decreased. Combined with our previous studies, age-related decreases in the number of nNOS-immunoreactive neurons in the central autonomic nucleus and the superficial dorsal horn might be associated with the abnormality of micturition function or pain perception encountered in the elderly. However, the mechanisms underlying the decreased immunoreactivity for nNOS, and the functional implications require elucidation.     

福尔马林致痛后大鼠中脑导水管周围灰质甲啡肽及脊髓背角P物质含量的变化

本文用免疫组化方法结合计算机图像处理技术观察大鼠后脚掌皮下注射福尔马林后脊髓背角Ｐ物质免疫阳性反应（ＳＰＬＩ）变化的节段性分布及中脑导水管周围灰质（ＰＡＧ）内甲啡肽样免疫阳性反应（ＭＥＬＩ）的变化。结果显示,注射福尔马林后,脊髓腰段（Ｌ１－２,Ｌ４－５）背角ＳＰＬＩ显著增强（Ｐ＜．０５）,３０ｍｉｎ组与６０ｍｉｎ组相比较无显著变化（Ｐ＞０．０５）;胸脊髓（Ｔ８）无显著变化（Ｐ＞０．０５）;颈脊髓背角ＳＰＬＩ有增强趋势（０．０５＜Ｐ＜０．１）;ＰＡＧ中ＭＥＬＩ减弱,腹外侧部３０ｍｉｎ组比６０ｍｉｎ组变化更大（Ｐ＜０．０５）。ＰＡＧ中ＭＥＬＩ与脊髓背角ＳＰＬＩ变化的时相关系提示福尔马林致痛引起的脊髓背角Ｐ物质的增多可能与ＰＡＧ中甲啡肽及阿片受体活动有关。     

Plasticity and emerging role of BKCa channels in nociceptive control in neuropathic pain

Large‐conductance Ca²⁺‐activated K⁺ (BK_Ca, MaxiK) channels are important for the regulation of neuronal excitability. Peripheral nerve injury causes plasticity of primary afferent neurons and spinal dorsal horn neurons, leading to central sensitization and neuropathic pain. However, little is known about changes in the BK_Ca channels in the dorsal root ganglion (DRG) and spinal dorsal horn and their role in the control of nociception in neuropathic pain. Here we show that L5 and L6 spinal nerve ligation in rats resulted in a substantial reduction in both the mRNA and protein levels of BK_Ca channels in the DRG but not in the spinal cord. Nerve injury primarily reduced the BK_Ca channel immunoreactivity in small‐ and medium‐sized DRG neurons. Furthermore, although the BK_Ca channel immunoreactivity was decreased in the lateral dorsal horn, there was an increase in the BK_Ca channel immunoreactivity present on dorsal horn neurons near the dorsal root entry zone. Blocking the BK_Ca channel with iberiotoxin at the spinal level significantly reduced the mechanical nociceptive withdrawal threshold in control and nerve‐injured rats. Intrathecal injection of the BK_Ca channel opener [1,3‐dihydro‐1‐[2‐hydroxy‐5‐(trifluoromethyl)phenyl]‐5‐(trifluoromethyl)‐2H‐benzimidazol‐2‐one] dose dependently reversed allodynia and hyperalgesia in nerve‐ligated rats but it had no significant effect on nociception in control rats. Our study provides novel information that nerve injury suppresses BK_Ca channel expression in the DRG and induces a redistribution of BK_Ca channels in the spinal dorsal horn. BK_Ca channels are increasingly involved in the control of sensory input in neuropathic pain and may represent a new target for neuropathic pain treatment.     

Molecular mechanism of changes in the morphine-induced pharmacological actions under chronic pain-like state: suppression of dopaminergic transmission in the brain

In the present study, we demonstrated whether a neuropathic pain-like state induced by sciatic nerve ligation in rodents could cause a long-lasting change in intracellular signaling in both supraspinal and spinal cord related to the suppression of morphine's effect. Mice with sciatic nerve ligation exhibited a significant suppression of the morphine-induced antinociception. Under this condition, phosphorylated-conventional protein kinase C-like immunoreactivity (p-cPKC-IR) and phosphorylated-micro-opioid receptor (p-MOR)-IR were clearly increased on the ipsilateral side in the dorsal horn of the spinal cord of nerve-ligated mice. It is of interest to note that astroglial hypertrophy as well as its proliferation was also noted in this area of sciatic nerve-ligated mice. Like nerve injury, the increase in cPKC activities and astroglial hypertrophy/proliferation in this region was observed by repeated morphine treatment. These findings suggest that the phosphorylation of both cPKC and MOR in the dorsal horn of the spinal cord by sciatic nerve ligation may play a substantial role in the suppression of morphine-induced antinociception under a neuropathic pain-like state. Sciatic nerve injury also caused a significant inhibition of MOR-mediated G-protein activation onto GABAergic neurons and a dramatic reduction in ERK activities onto dopaminergic neurons in the ventral tegmental area (VTA) regulating the rewarding effect of opioids. Furthermore, we found that the inhibition of ERK cascade in the VTA by treatment with specific inhibitors suppressed the morphine-induced rewarding effect in normal mice. These findings provide evidence that the direct reduction in MOR function and the persistent decrease in ERK activity of dopaminergic neurons in the VTA may contribute to the suppression of the morphine-induced rewarding effect under a neuropathic pain-like state. Conclusively, our recent findings provide novel evidences for the mechanism underlying the less sensitivity to opioids under a neuropathic pain-like state.     

Direct evidence for spinal cord microglia in the development of a neuropathic pain-like state in mice

The present study was undertaken to further investigate the role of glial cells in the development of the neuropathic pain-like state induced by sciatic nerve ligation in mice. At 7 days after sciatic nerve ligation, the immunoreactivities (IRs) of the specific astrocyte marker glial fibrillary acidic protein (GFAP) and the specific microglial marker OX-42, but not the specific oligodendrocyte marker O4, were increased on the ipsilateral side of the spinal cord dorsal horn in nerve-ligated mice compared with that on the contralateral side. Furthermore, a single intrathecal injection of activated spinal cord microglia, but not astrocytes, caused thermal hyperalgesia in naive mice. Furthermore, 5-bromo-2'-deoxyuridine (BrdU)-positive cells on the ipsilateral dorsal horn of the spinal cord were significantly increased at 7 days after nerve ligation and were highly co-localized with another microglia marker, ionized calcium-binding adaptor molecule 1 (Iba1), but neither with GFAP nor a specific neural nuclei marker, NeuN, in the spinal dorsal horn of nerve-ligated mice. The present data strongly support the idea that spinal cord astrocytes and microglia are activated under the neuropathic pain-like state, and that the proliferated and activated microglia directly contribute to the development of a neuropathic pain-like state in mice.     

促肾上腺皮质激素对慢痛大鼠脊髓生长抑素、c-fos表达及痛反应的影响

本研究应用免疫组化、原位杂交和痛级均数测定法,探讨鞘内注射促肾上腺皮质激素（ＡＣＴＨ）对甲醛引起大鼠脊髓内生长抑素（Ｓｏｍ）、ｃｆｏｓ表达及痛反应的影响。结果表明,足底注射甲醛可使大鼠脊髓内ｃｆｏｓ样免疫反应（ＦＬＩ）、Ｓｏｍ样免疫反应（ＳｏｍＬＩ）、ＦＬＩ／ＳｏｍＬＩ及前Ｓｏｍ原ｍＲＮＡ（ＰＰＳｍＲＮＡ）神经元数目显著增多以及痛级均数（ＰＩＲ）显著升高。而鞘内注射ＡＣＴＨ可显著抑制甲醛引起的大鼠脊髓内ＦＬＩ、ＳｏｍＬＩ、ＦＬＩ／ＳｏｍＬＩ及ＰＰＳｍＲＮＡ增多和ＰＩＲ升高效应。鞘内预先注射赛庚啶可阻断ＡＣＴＨ的抑制效应,而荷包牡丹碱、纳洛酮则无影响。结果提示,５羟色胺受体可能参与ＡＣＴＨ抑制甲醛引起的痛反应。     

周围神经损伤后外源性GKNF对神经元的保护作用

采用硅管套接大鼠切断的坐骨神经模型,局部给予胶质细胞源性神经营养因子（ＧＤＮＦ）,应用尼氏染色、酶组织化学染色方法,观察到外源性ＧＤＮＦ能减少脊髓修复侧前角运动神经元死亡的数目,降低脊髓前角运动神经元及脊神经节感觉神经元中胆碱酯酶（ＣＨＥ）及酸性磷酸酶（ＡＣＰ）变化的幅度。这表明外源性ＧＤＮＦ能保护周围神经切断后引起的神经元损伤．     

Time Course of Immediate Early Gene Protein Expression in the Spinal Cord following Conditioning Stimulation of the Sciatic Nerve in Rats

Long-term potentiation induced by conditioning electrical stimulation of afferent fibers is a widely studied form of synaptic plasticity in the brain and the spinal cord. In the spinal cord dorsal horn, long-term potentiation is induced by a series of high-frequency trains applied to primary afferent fibers. Conditioning stimulation (CS) of sciatic nerve primary afferent fibers also induces expression of immediate early gene proteins in the lumbar spinal cord. However, the time course of immediate early gene expression and the rostral-caudal distribution of expression in the spinal cord have not been systematically studied. Here, we examined the effects of sciatic nerve conditioning stimulation (10 stimulus trains, 0.5 ms stimuli, 7.2 mA, 100 Hz, train duration 2 s, 8 s intervals between trains) on cellular expression of immediate early genes, Arc, c-Fos and Zif268, in anesthetized rats. Immunohistochemical analysis was performed on sagittal sections obtained from Th13- L5 segments of the spinal cord at 1, 2, 3, 6 and 12 h post-CS. Strikingly, all immediate early genes exhibited a monophasic increase in expression with peak increases detected in dorsal horn neurons at 2 hours post-CS. Regional analysis showed peak increases at the location between the L3 and L4 spinal segments. Both Arc, c-Fos and Zif268 remained significantly elevated at 2 hours, followed by a sharp decrease in immediate early gene expression between 2 and 3 hours post-CS. Colocalization analysis performed at 2 hours post-CS showed that all c-Fos and Zif268 neurons were positive for Arc, while 30% and 43% of Arc positive neurons were positive for c-Fos and Zif268, respectively. The present study identifies the spinal cord level and time course of immediate early gene (IEGP) expression of relevance for analysis of IEGPs function in neuronal plasticity and nociception.     

不同频率电针刺激对神经痛模型大鼠脊髓背角P物质的影响

目的:观察P物质(Substance P,SP)在慢性坐骨神经压迫损伤(chronic constriction injury,CCI)模型脊髓中表达的变化,探讨电针镇痛的机制是否与脊髓背角中SP表达的变化有关。方法:选择32只雄性、体重180-200 g的SD大鼠,并将其随机均分为4组(n=8)。空白组(Con组)为正常痛阈值大鼠;假电针组(CCI+A组)在损伤的坐骨神经旁置入电针,但无电流刺激;2 Hz组和100Hz组分别给予相应频率电流刺激30 min。在实验开始前和术后1、4、7、14、20、22天记录大鼠的热缩足反射潜伏期(Paw Withdrawal Latency,PWL)和机械刺激缩足反射阈值(Paw Withdrawal Threshold,PWT)。免疫组化方法检测脊髓背角SP的表达。结果:术后20天,电针治疗后,100 Hz组和2 Hz组PWT分别为(7.33±1.42)g和(7.80±1.42)g,均显著高于假电针组(2.60±1.46)g,差异有统计学意义(P0.05)。100 Hz组在术后20天后和2 Hz组在术后14天后PWL值均显著高于假电针组,差异有统计学意义(P0.05)。免疫组化显示:2 Hz组和100 Hz组大鼠脊髓背角中P物质阳性细胞显著低于假电针组(P0.05)。结论:坐骨神经旁电针刺激能够显著减轻CCI模型大鼠热痛觉及机械痛觉过敏,其机制可能与抑制脊髓背角SP的表达有关。     

大鼠脊髓诱发电位与脊髓损伤的关系——Ⅲ.脊髓局部损毁后电位的变化及电位来源分析

本文描述了大鼠脊髓L_1节段后柱、后索、侧索和前角的诱发电位及其损伤后的变化,并观察了切断L_4、L_5脊神经背、腹根与横断高位颈髓对电位的影响,以进行行电位来源分析。结果可见,上述四个区域的诱发电位基本由早反应三相波和晚反应组成。分别电解损毁这些部位后,电位波幅均普遍降低,晚期反应较早反应降低明显。后柱或后索受损对电位影响最大。局部损毁后可见L_1及T_(13)水平的硬膜上电位改变明显,尤其晚反应减弱、波峰平坦。反应时值与潜伏时未见明显改变。切断L_4脊神经背、腹根后、电位基本消失。去大脑对电位未见明显影响。结果表明,刺激坐骨神经诱发的脊髓电位起源于低位腰段传入神经和脊髓内多通路的兴奋传导,在一定程度上受腹根逆行活动的影响,与大脑及脊髓下行传导束活动无直接联系。脊髓诱发电位的幅度与波形改变可作为脊髓损伤的判断指标之一。     

Somatostatin-, calcitonin gene-related peptide, and gamma-aminobutyric acid-like immunoreactivitity in the frog lumbosacral spinal cord: distribution and effects of sciatic nerve transection

Using immunohistochemistry and optical densitometry, somatostatin (SOM), calcitonin gene-related peptide (CGRP), and gamma-aminobutyric acid (GABA) were investigated in the lumbosacral spinal cord of the frog Rana catesbeiana after sciatic nerve transection. In control animals, the densest network of the SOM-, CGRP- and GABA-like immunoreactive fibers was located in the dorsal part of the lateral funiculus. SOM and GABA-like fibers were found in the dorsal terminal field and in the mediolateral band. The latter region showed CGRP and SOM-like immunoreactive cell bodies. SOM- and GABA-like immunoreactive neurons also occurred around the cavity of the central canal, and other GABA-like fibers were found in the ventral terminal field. While the ventral horn showed scarce somatostatin-like fibers, the putative motoneurons were immunoreactive for the two peptides investigated and GABA, but only a few SOM- and GABA-like fibers occurred in the ventral funiculus. After axotomy, GABA-like immunoreactivity decreased in the dorsal part of the lateral funiculus on the same side of the lesion. The other regions remained labeled. These changes were observed at 3 days following axonal injury and persisted at 5, 8 and 15 days. There was no significant difference in the pattern of CGRP- and SOM- immunoreactivity between the axotomized and the control sides. These results are discussed in relation to the effects of the peripheral axotomy on GABA, SOM, and CGRP expression in vertebrates, emphasizing the use of frogs as a model to study the effects of peripheral nerve injury.     

Effect of aging on the substance P receptor, NK-1, in the spinal cord of rats with peripheral nerve injury

Substance P (SP) levels in the spinal cords of very old rats are less than the levels in younger rats (Bergman et al., 1996). After injury to a peripheral nerve in young rats, immunoreactivity (ir) to the SP receptor, NK-1 (neurokinin-1), increases in the spinal cord ipsilateral to the injury and the increases are correlated with the development of thermal hyperalgesia (Goff et al., 1998). Thus we postulated that aged rats might display an increased sensitivity to thermal stimulation before peripheral nerve injury and that they might respond differently to injury than do younger rats. To test this hypothesis, we used the Bennett and Xie model (1988) of chronic constriction injury (CCI) to the sciatic nerve to induce a neuropathic pain condition. We investigated the effect of age on changes in NK-1 ir in superficial layers of the dorsal horn and on numbers of NK ir cells in deeper laminae at the L4-L5 levels of the spinal cord after CCI. NK-1 receptors were tagged immunohistochemically and their distribution quantified by use of computer-assisted image analysis. NK-1 ir changes were related to alterations in thermal and tactile sensitivity that developed after CCI in young, mature and aged (4-6, 14-16, and 24-26 months) Fischer F344 BNF1 hybrid rats. No differences in thermal or tactile sensitivity of young and aged rats were seen in the absence of nerve injury. After injury, aged rats developed thermal hyperalgesia and tactile allodynia more slowly than did the younger rats. NK-1 receptor ir and numbers of NK-1 ir cells in the dorsal horn increased with time post-injury in all three groups. NK-1 ir increases were correlated with the development of thermal hyperalgesia in those rats that displayed hyperalgesia. However, some rats developed an increased threshold to thermal stimuli (analgesia) and that also was correlated with increases in NK-1 ir. Thus NK-1 ir extent, while correlated with thermal sensitivity in the absence of injury, is not a specific marker for disturbances in one particular sensory modality; rather it increases with peripheral nerve injury per se.     

周围神经损伤后外源性GDNF对神经元的保护作用

采用硅管套接大鼠切断的坐骨神经模型 ,局部给予胶质细胞源性神经营养因子 (GDNF) ,应用尼氏染色、酶组织化学染色方法 ,观察到外源性GDNF能减少脊髓修复侧前角运动神经元死亡的数目 ,降低脊髓前角运动神经元及脊神经节感觉神经元中胆碱酯酶 (CHE)及酸性磷酸酶 (ACP)变化的幅度。这表明外源性GDNF能保护周围神经切断后引起的神经元损伤。