Comparison of five different rat models of peripheral nerve injury

Described here is a comparison of five peripheral sciatic nerve injury models in rats which all result in various degrees of neuropathic pain symptoms. They are the chronic constriction injury (CCI), the spinal nerve ligation (SNL), the partial sciatic ligation (PSL), the tibial and sural transection (TST), and the complete sciatic transection (CST) model. Behavioral testing was performed on these models over a 56-day period under strict experimental conditions to minimise variability between the surgical models and to allow for an accurate evaluation of the sensory deficits produced by each model. Overall, all five models of neuropathic pain produced signs of allodynia and hyperalgesia to various stimuli. However, the duration and magnitude of the evoked responses varied considerably between the different models.     

Behavioral pharmacological characterization of mice lacking the nociceptin receptor]

Nociceptin and nociceptin receptor, which show structural similarities to opioid peptides and opioid receptors, respectively, have been recently found to constitute a novel neuromodulatory system. In the central nervous system, however, the physiological role of modulation via the nociceptin receptor is still unclear. Here, we report the behavioral pharmacological characterization of mice lacking the nociceptin receptor. Nociceptin produced hyperalgesia and hypolocomotion, whereas the nociceptin receptor-knockout mice showed no significant abnormalities in nociceptive thresholds (tail-flick, hot-plate, electric, and acetic acid-induced writhing tests) and locomotion. In the learning and memory tests, nociceptin induced impairment of learning and memory in wild-type mice. Nociceptin receptor-knockout mice possessed greater learning ability and had better memory than wild-type mice. These results suggest that the nociceptin system plays a role in regulation of nociception or locomotion and seems to play negative roles in learning and memory. Next, we compared nociceptive responses induced by various opioids between the nociceptin receptor-knockout and wild-type mice. As previously reported, morphine (mu-opioid receptor agonist), U-50,488 H (kappa 1-opioid receptor agonist), and naloxone benzoylhydrazone (NalBzoH; kappa 3-opioid receptor agonist) induced antinociceptive effects in wild-type mice. Surprisingly, knockout mice lacked the antinociceptive effect induced by NalBzoH, but not by morphine and U-50,488H. Further, NalBzoH completely inhibited nociceptin-induced hyperalgesia and hypolocomotion in wild-type mice. Experiments on the cultured cells transfected with the nociceptin receptor cDNA showed that NalBzoH competed in [3H]-nociceptin binding and attenuated the nociceptin-induced inhibition of cyclic AMP accumulation induced by forskolin. These results clearly suggest that NalBzoH acts as a potent antagonist for the nociceptin receptor. Our studies suggest that the nociceptive system and/or learning and memory processes could be modulated by ligands to the nociceptin receptor, and further that the antagonists are worth testing for the alleviation of pain and memory disorders.     

周围神经损伤的显微外科修复

目的 分析应用显微外科技术修复周围神经损伤的临床疗效.方法 自1997～2009年,用显微外科技术修复周围神经损伤176例197条神经,方法包括神经外膜缝合术、神经束膜缝合术、神经松解术及神经移植术.结果 术后经3～60个月随访,根据BMRC感觉、运动评价标准,其中疗效为优者84条,良者77条,优良率达81.73%.伤后24 h内修复者的优良率为93.52%,优于3个月内修复者.3个月内修复者优良率为79.31%,优于6个月后修复者.结论 应用显微外科技术对周围神经损伤的早期修复和显微镜下神经断端的精确对合可提高临床疗效.     

Chronic exposure to n-hexane induces changes in nerve-specific marker proteins in the distal peripheral nerve of the rat.

1. After long-term n-hexane exposure (2000 ppm, 12 h d-1, 6 d week-1, for 24 weeks), the content of neuron-specific enolase (gamma-enolase), creatine kinase-B and beta-S100 protein in the cortex, cerebellum, spinal cord and proximal and distal sciatic nerves of rats was determined by enzyme immunoassay. 2. The amounts of the three proteins decreased significantly in the distal segment of sciatic nerve, whereas they remained unchanged in the brain and proximal sciatic nerve. The quantitative decline in these marker proteins in the distal sciatic nerve could be related to neurophysiological deficits in the peripheral nerves. 3. This study indicates that the biochemical changes observed are consistent with the clinical and pathological findings of n-hexane neuropathy. These nerve-specific marker proteins can be used to assess solvent-related peripheral neurotoxicity.     

壳聚糖在周围神经损伤修复中的应用

壳聚糖的细胞亲和性和修复外周神经损伤等方面的研究都有新的进展。壳聚糖作为外周神经损伤修复材料有良好的研究应用价值和开发前景。此文介绍了壳聚糖在修复外周神经损伤中的研究现状。     

Inhibition of sciatic nerve sterologenesis in hexacarbon-induced distal axonopathy in the rat

Sterologenesis from [¹⁴C]acetate and [³H]mevalonolactone has been studied, in vitro, in sciatic nerves of rats fed 1% 2,5-hexanedione in the drinking water for 6 weeks. Nerves from rats given 2,5-hexanedione, in comparison with those from pair-fed control rats, exhibited reduced incorporation of [¹⁴C]acetate, but not of [³H]mevalonolactone, into the sterol precursor squalene (38%), C₃₀ sterols (53%), C₂₇ sterols (46%), and digitonin-precipitable sterols (41%). Sterologenesis was not inhibited in nerves obtained from untreated rats and incubated in vitro with 1 mm 2,5-hexanedione, nor in nerves of rats that had inhaled 1000 ppm n-hexane for 6 hr. Incorporation of [¹⁴C]acetate into triacylglycerols of nerves from rats exposed to n-hexane was increased by 50%; [¹⁴C]acetate incorporation into other lipid fractions was similar in n-hexane-exposed and control rats. The concentration of 2,5-hexanedione in nerves of rats receiving 1% 2,5-hexanedione in drinking water for 6 weeks or exposed to 1000 ppm n-hexane for 6 hr was determined by gas chromatography-mass spectrometry and found to be 0.8 ± 0.2 and 5.2 ± 0.6 μg/g tissue wet weight, respectively.     

Biochemical and pharmacological characterization of the serotonin transporter in human peripheral blood lymphocytes.

The serotonin transporter (5-HTT) plays a critical role in the termination of serotonin neurotransmission and represents the prime target for selective serotonin reuptake inhibitors (SSRIs). In the present study, the 5-HTT protein in human peripheral blood lymphocyte was characterized pharmacologically and biochemically. The tricyclic antidepressant drug [(3)H]imipramine, an established ligand for the neuronal and platelet 5-HTT, bound saturably and reversibly to a single population of non-interacting binding sites in fresh human peripheral blood lymphocytes. The affinity of [(3)H]imipramine (K(d)) to the transporter, calculated from association and dissociation kinetic experiments, was similar to that obtained from the equilibrium study. The function of the transporter was studied using high affinity [(3)H]5-HT uptake into fresh lymphocytes. [(3)H]Imipramine binding and [(3)H]5-HT uptake were inhibited by tricyclic antidepressants as well as by SSRIs. Western blot analysis as well as immunoprecipitation analysis revealed labeling of a single protein band of approximately 100 kDa. The presence of the 5-HTT in easily accessible nucleated cells such as peripheral blood lymphocytes might permit molecular genetic studies in mood and anxiety disorder patients, and might enhance the understanding of the different efficacies of antidepressants in depressed patients.     

Caffeine-induced epileptiform field potentials in rat hippocampal slices: a pharmacological characterization

Pharmacological modulation of the epileptiform electric activity induced by caffeine, 10 mM (CAF) on rat hippocampal slices was studied upon field potential recordings in CA3 area of the slices. This concentration of CAF, reportedly releasing Ca2+ ions from the endoplasmic reticulum, led single fimbrial stimuli to evoke repetitive population spikes (PSs) and induced periodic spontaneous field bursts. Carbamazepine, 50 microM reduced (by <40%) the number of repetitive PSs and the rate of spontaneous bursting, with no significant effect on the amplitude of evoked and spontaneous bursts. Valproate, 1 mM reduced only the number (by approximately 25%), but not the amplitudes, of repetitive PSs. Clonazepam, 1 microM consistently reduced the number of repetitive PSs (by approximately 45%), their amplitudes (by 30-60%), and the amplitude of spontaneous bursts (by approximately 70%). The adenosine receptor agonists 2-chloroadenosine, 5 microM and R(-) N6-(2-phenylisopropyl)adenosine, 1 microM had only scanty anti-CAF activity. The depletor of intracellular Ca2+ stores, thapsigargin, 2 microM transiently inhibited the number of evoked PSs and spontaneous bursting. The blocker of ryanodine receptor opening, ruthenium red had an anti-CAF effect, modest at 30 microM, but very strong at 40 microM. Nifedipine, 20 microM opposed CAF-induced spontaneous bursting, but not the evoked PSs. Flunarizine, 50 microM presented only a transient tendency to delay spontaneous bursting. In conclusion, this in vitro slice model appears readily able to reveal antiepileptic properties, though it does not support unequivocal mechanistic interpretation. Nevertheless, anti-CAF activity in this model would suggest the likely involvement of the neuronal ryanodine receptor-related traffic of calcium.     

神经妥乐平对周围神经损伤的治疗作用

目的 :观察神经妥乐平对周围神经损伤病人的疗效。方法 :86例周围神经损伤病人在常规治疗基础上随机分为神经妥乐平治疗组 44例 ,给神经妥乐平wk 1～ 2 ,6mL ,iv,qd或 3mL ,im ,qd ,wk3～4改为口服 ,2片 ,bid ;对照组 42例仅进行常规治疗。治疗前后观察疼痛、麻木、感觉减退、感觉过敏、乏力等指标的改善情况。结果 :神经妥乐平组的改善率分别为 87% (疼痛 )、88% (乏力 )、88% (感觉减退 )、62 % (麻木 )、5 6% (感觉过敏 )。疼痛与乏力和对照组相比 ,差异有显著意义 (P <0 .0 5 )。神经妥乐平组总有效率在治疗 4wk时为 1 0 0 % ,对照组为 69% ,2组间比较经Ridit分析差异有非常显著意义 (P <0 .0 1 )。结论 :神经妥乐平可安全、有效治疗周围神经损伤     

Localization and pharmacological characterization of somatostatin sst2 sites in the rat cerebellum

Radioligand binding studies were performed in membranes of rat cerebellum using [¹²⁵I]-[Tyr³]octreotide ([¹²⁵I]204-090) to characterize the nature of cerebellar somatostatin receptors. Saturation experiments suggest the presence of a single class of binding sites with high affinity, pK_d = 9.53 ± 0.11, but low receptor density, B _max = 12.7 ± 1.0 fmol/mg protein. The pharmacological profile of [¹²⁵I]204-090 sites in cerebellar membranes was established using a range of ligands known to interact with SSTR-2 (now called sst₂) and other somatostatin (SRIF) receptors. SRIF analogues such as octreotide (SMS 201-995), seglitide (MK 678) and somatuline (BIM 23014) displayed very high affinity for cerebellar [¹²⁵I]204-090 binding sites. The data were compared to results obtained using the same ligand in rat cerebral cortex membranes known to represent sst₂ binding. The pharmacological characteristics of the cerebellar sites were in close correlation with those of the cerebral cortex (r = 0.976, n = 19, p < 0.001) and CHO-cells expressing human recombinant sst₂ receptor (r = 0.977, n = 19, p < 0.001). By contrast, there was very little correlation between cerebellar binding and published affinities for rat sst₅ receptors (r = 0.465), for which octreotide has also high affinity. In vitro autoradiographic studies performed in cerebellar slices using [¹²⁵I]204-090 demonstrated the presence of binding sites in the molecular layer of the rat cerebellum. In situ hybridization studies using sst₂ receptor mRNA selective oligoprobes confirmed the presence of sst₂ receptor mRNA in the rat cerebellum. Together, the present data demonstrate the presence of a low density of SRIF receptors in the molecular layer of the adult rat cerebellum which are best characterized as sst₂. This is the first pharmacological characterization and localization of sst₂ receptors in the adult rat cerebellum.     

Death in pain: peripheral nerve injury and spinal neurodegenerative mechanisms

A complex network operates in the spinal dorsal horn to integrate peripheral nociceptive inputs with local and descending control mechanisms, and to cross-talk with higher brain areas. Injury to peripheral sensory nerves can trigger a cascade of events within this relay which, in some cases, may turn into abnormal responses outlasting the initial detrimental stimulus and leading to chronic pain. In the spinal dorsal horn, evidence has been provided both in support and against the occurrence of neuronal loss following peripheral nerve injury, leaving this issue still unresolved. Only new conceptual and technical approaches will determine the relevance of spinal neurodegenerative mechanisms to chronic pain states and allow translation into novel therapeutic targets.     

N,N-diethyldithiocarbamate produces copper accumulation, lipid peroxidation, and myelin injury in rat peripheral nerve.

Previous studies have demonstrated the ability of the dithiocarbamate, disulfiram, to produce a peripheral neuropathy in humans and experimental animals and have also provided evidence that N,N-diethyldithiocarbamate (DEDC) is a proximate toxic species of disulfiram. The ability of DEDC to elevate copper levels in the brain suggests that it may also elevate levels of copper in peripheral nerve, possibly leading to oxidative stress and lipid peroxidation from redox cycling of copper. The study presented here investigates the potential of DEDC to promote copper accumulation and lipid peroxidation in peripheral nerve. Rats were administered either DEDC or deionized water by ip osmotic pumps and fed a normal diet or diet containing elevated copper, and the levels of metals, isoprostanes, and the severity of lesions in peripheral nerve and brain were assessed by ICP-AES/AAS, GC/MS, and light microscopy, respectively. Copper was the only metal that demonstrated any significant compound-related elevations relative to controls, and total copper was increased in both brain and peripheral nerve in animals administered DEDC on both diets. In contrast, lesions and elevated F2-isoprostanes were significantly increased only in peripheral nerve for the rats administered DEDC on both diets. Autometallography staining of peripheral nerve was consistent with increased metal content along the myelin sheath, but in brain, focal densities were observed, and a periportal distribution occurred in liver. These data are consistent with the peripheral nervous system being more sensitive to DEDC-mediated demyelination and demonstrate the ability of DEDC to elevate copper levels in peripheral nerve. Additionally lipid peroxidation appears to either be a contributing event in the development of demyelination, possibly through an increase of redox active copper, or a consequence of the myelin injury.     

神经生长因子对周围神经损伤的保护作用

以小鼠化学性交感神经末梢损伤、家兔尺神经机械损伤为模型及用新生大鼠背根神经节体外无血清培养法,研究神经生长因子(NGF)对周围神经损伤及感觉神经元的保护作用。结果表明,NGF剂量依赖地提高小鼠颌下腺去甲肾上腺素残留率,提高损伤后兔C₇,T₁背根神经节的细胞数,显著促进新生大鼠背根神经节突起的生长。结果提示,NGF对周围神经损伤有明显的保护作用,并对感觉神经元有很强的神经营养作用。     

Nanofiber scaffolds facilitate functional regeneration of peripheral nerve injury

Peripheral nerve injury still remains a refractory challenge for both clinical and basic researchers. A novel nanofiber conduit made of blood vessel and filled with amphiphilic hydrogel of self-assembling nanofiber scaffold (SAPNS) was implanted to repair a 10 mm nerve gap after sciatic nerve transection. Empty blood vessel conduit was implanted serving as control. Results showed that this novel nanofiber conduit enabled the peripheral axons to regenerate across and beyond the 10 mm gap. Motoneuron protection, axonal regeneration and remyelination were significantly enhanced with SAPNS scaffold treatments. The target reinnervation and functional recovery induced by the regenerative nerve conduit suggest that SAPNS-based conduit is highly promising application in the treatment of peripheral nerve defect.From the Clinical EditorIn this paper by Zhan et al, a novel self-assembling nanofiber scaffold is reported to promote regeneration of peripheral nerves in a sciatic nerve injury model. The promising results and the obvious medical need raises hope for a clinical translation of this approach hopefully in the near future.     

人组织激肽释放酶对周围神经系统损伤后的修复效应

目的:评价人组织激肽释放酶(HTK)促进周围神经系统损伤后的修复作用.方法:取30只体重180～200 g的雄性SD大鼠,随机分成3组:假手术组、HTK组(17.5×10~(-3) PNAU/kg)、对照组,每组各10只.术前第0天和术后第1、第3、第5、第7、第9、第11、第13天测定坐骨神经功能指数(SFI)以及静止坐骨神经指数(SSI),术后第14天测定坐骨神经干动作电位传导速度(NCV).结果:SFI、SSI值在假手术组手术前后未见明显改变.HTK组和对照组中,术后第1天SFI、SSI均为-100左右.以后发现HTK组的SFI、SSI恢复的情况要优于对照组,从第5天开始两组SFI、SSI值有统计学差异(P<0.05).术后第14天HTK组的NCV值要高于对照组,两组间有统计学差异(P<0.05).结论:HTK具有促进周围神经系统损伤后的修复作用.     

Altered hippocampal long-term potentiation after peripheral nerve injury in mice

It has been clinically reported that patients with chronic pain often have accompanying cognitive deficiency, which hampers efficient medical treatment. In the present study, we investigated whether hippocampal synaptic plasticity, which has been considered to be a cellular model of learning and memory, could be influenced by chronic pain conditions using a murine model of neuropathic pain prepared by partial ligation of the sciatic nerve (the Seltzer model). In slices obtained from neuropathic animals, tetanus-induced long-term potentiation of CA1 hippocampal synaptic transmission was impaired, whereas long-term depression induced by low-frequency stimulation was similar in neuropathic and sham-treated (control) animals. Bath application of the beta-adrenoceptor agonist isoproterenol or the beta-adrenoceptor antagonist propranolol diminished the difference of synaptic plasticity between neuropathic and control mice. In the presence of isoproterenol, long-term potentiation was successfully induced in neuropathic mice. By contrast, long-term potentiation in sham-treated mice was impaired by propranolol which did not alter the already impaired long-term potentiation after peripheral nerve injury. These results suggest that beta-adrenergic functions are changed in chronic pain conditions, which may underlie the deficiency of long-term potentiation.     

A characterization of nicotine-induced tolerance: evidence of pharmacological tolerance in the rat

The present studies were conducted in order to confirm and extend previous findings that the mechanisms of tolerance to the behaviorally disruptive effects of nicotine in a operant model were primarily pharmacological. Both the traditional methodology employing the determination of dose response curves before and after chronic drug administration and a methodology which omits the generation of dose response curves were utilized in these investigations of nicotine-induced tolerance. Rats developed tolerance to both pre- and post-session administration of nicotine, suggesting that the mechanisms of tolerance to the disruptive effects of nicotine are primarily pharmacological. The mechanisms underlying these effects, however, remain to be evaluated.