Effects of verapamil on behavioral and microcirculatory disorders in pain syndrome of spinal etiology

In the experiments on Wistar rats with pain syndrome of spinal origin (PSSO) caused by the generator of pathologically enhanced excitation (GPEE) in dorsal horns of the spinal cord lumbosacral segments, it was shown that the intravenous verapamil injection (1.25 mg/kg) undoubtedly decreased behaviour response and improves the state of microcirculation. The compound of 10-fold decreased dose does not affect the behaviour response and microcirculation. When PSSO exists, the intravenous injection of analgin (150 mg/kg) produced an effect on the behaviour response and does not produce any action on microcirculation. When verapamil reaches the dorsal surface of the spinal cord (GPEE area) it decreases the behaviour response and microcirculation disorders created in PSSO. The obtained data make it clear that the GPEE depression caused by the verapamil calcium channel blocker weakens PSSO and normalizes the microcirculation.     

Effect of dopamine antibodies on neuropathic pain syndrome in rats

Dopaminergic brain system plays an important role in regulation of pain sensitivity. However, the data on participation of antidopamine antibodies in the development of neurogenic pain are absent. This work was aimed at the study of the role of antidopamine antibodies in the development of pain syndrome induced by the injury of nn. ischiadic and saphenous in rats. It was shown that after the nerve injury, the behavioral reaction such as autotomy (self-injury) appeared as a feature of the experimental neuropathic pain syndrome. It was originally established that the development of neuropathic pain syndrome induced by the injury of peripheral nerves was accompanied by induction of dopamine autoantibodies. It was also shown that immunization of the animals with conjugated dopamine-protein autigen resulted in aninerease of autidopamine antibody level and an amplification of the experimental neuropathic pain syndrome, i.e., decrease in the latency of the first autotomy, increase in expression of autotomies, and increase in the number of animals with late autotomies.     

Frontal deafferentation of the mediobasal hypothalamus in the neonatal rat and its effects on the preoptico-infundibular LHRH-tract

Summary By use of the peroxidase-antiperoxidase-complex (PAP) immunohistological method, the preoptico-infundibular LHRH-tract was studied in adult female rats in which frontal hypothalamic deafferentation was performed at the third or tenth postnatal day. In the former group, this LHRH-tract appeared to be similar to that of the intact controls; the animals showed regular vaginal cycles and ova were present in their oviducts. In the latter group, however, marked reduction in the number of the LHRH-nerve fibers was observed behind the sites of the deafferentation in the mediobasal hypothalamus (MBH), whereas LHRH-immunoreactive perikarya and nerve fibers containing the immunoreactive material were seen rostral to the plane of severance. In these animals reduction of LHRH-fibers in the MBH was accompanied by an anovulatory syndrome characterized by constant vaginal cornification and polyfollicular ovaries. Comparing the glial scar formation induced by the cut, significant differences were detected between the two experimental groups. In the animals deafferented on the 3rd day of life, reduction of nerve cells was seen along the cut, but LHRH-fibers crossing the thin glial scar were detectable in large numbers. On the other hand, in the animals deafferented on the 10th postnatal day, extensive glial scar tissue appeared to interrupt the LHRH-fibers rostral to the cut.     

Epileptiform activity in the somatosensory cortex of rats with trigeminal neuralgia]

It was shown in experiments on rats that penicillin 1 microliter microinjection (100 U) into the caudal nucleus of the spinal tract of the trigeminal nerve, accounting for formation of a generator of pathologically enhanced excitation (GREE), brings about in rats the pain syndrome with characteristic for trigeminal neuralgia behavioural manifestations and the emergence of epileptiform activity in the somatosensory cortex, especially pronounced in the contralateral hemisphere. The emergence of this activity reflects, on the one hand, the action of the GREE in the caudal nucleus of the trigeminal nerve and, on the other hand, the involvement of the somatosensory cortex taking over stimulation from the hyperactive caudal nucleus, into formation of a pathological algic system of this form of trigeminal neuralgia.     

Analysis of the analgesic effects of tricyclic antidepressants on neuropathic pain,diabetic neuropathic pain,and fibromyalgia in rat models

ObjectiveTo investigate the analgesic effect of amitriptyline on neuropathic pain model rats, diabetic neuropathic pain model rats and fibromyalgia model rats.MethodsThe healthy male Sprague wrote – Dawley (SD) rats were taken as the research object, and they were randomly divided into model group (group A), beside the sciatic nerve and injection of 5 mm amitriptyline group (group B), beside the sciatic nerve and injection of 10 mm amitriptyline group (group C), beside the sciatic nerve and injection of 15 mm amitriptyline group (group D), intraperitoneal injection of amitriptyline group (group E). Pain induced by selective injury of sciatic nerve branches in rats, pain induced by chronic compression of sciatic nerve, diabetic neuropathic pain and fibromyalgia were conducted to determine the pain threshold of mechanical stimulation in rats after drug administration.ResultsThe pain threshold of mechanical stimulation in the local amitriptyline group (group B, C, D) was significantly higher than that in the group A and group E at each time point after drug treatment, and the pain threshold of mechanical stimulation gradually increased with the increase of concentration. There was no statistically significant difference in mechanical stimulation pain threshold between group A and group E at each time point after drug treatment.ConclusionPara-sciatic injection of amitriptyline at different concentrations has analgesic effects on neuropathic pain, diabetic neuropathic pain and fibromyalgia in rat models, and amitriptyline directly ACTS on the local sciatic nerve.     

Clinical experience with the CO2 laser during carpal tunnel decompression

Scar tissue formation along the cut edges of the transverse carpal ligament has been found to be among the primary causes for persistent median nerve compression following carpal tunnel release with the steel scalpel. Since laser surgery has been shown to be effective in reducing incisional inflammatory reactions, hypertrophic scarring, and postoperative pain and edema, in achieving better hemostasis, the application of the carbon dioxide laser may be a more efficient surgical tool than the steel scalpel for carpal tunnel release. In 46 cases of carpal tunnel syndrome, the carbon dioxide laser was utilized to vaporize the transverse carpal ligament and seal its edges. The patients were then reevaluated at 1 week, 2 weeks, 6 months, 1 year, and 2 years. No intraoperative complications were encountered. Patients reported minimal postoperative pain, rapid return of sensibility, decreased paresthesia, and increased motor function. After 2 years, there have been no recurrent symptoms of median nerve compression in these patients.     

Features of changes in bioelectric reactions of the cerebral cortex in rats with deafferentation pain syndrome]

In rats with pain syndrome after sciatic nerve section the authors studied spontaneous and evoked bioelectric activity in sensomotor cerebral cortex of both hemispheres. Electrocorticogram showed the presence of hyper-synchronic discharges and paroxysmal peak-wave (700-800 mV) activity in contralateral hemisphere. While stimulating the injured limb the threshold of evoked potentials (EP) was observed to decrease, its amplitude to increase and focus maximum EP activity to extend.     

大鼠坐骨神经切断后谷氨酰胺合成酶在DRG内的表达变化

目的:观察坐骨神经切断后不同时间点背根神经节(DRG)内谷氨酰胺转化酶(GS)的表达变化。方法:48只SD大鼠随机分为实验组和正常对照组,其中实验组左侧为对照侧,右侧行坐骨神经切断。实验组大鼠分别存活1、3、7、14或21天。免疫组化方法检测DRG中GS的表达。结果:正常组DRG内GS主要表达于卫星细胞。坐骨神经切断1天后GS表达增加,明显高于正常组(P<0.05),3天时GS表达下降,7d时恢复正常。14天、21天时GS表达继续下降,明显低于正常组(P<0.05)。实验组手术侧和对照侧GS表达无显著性差异(P>0.05)。结论:坐骨神经切断后DRG内GS表达存在时空变化,这可能与坐骨神经切断后DRG内谷氨酸介导的兴奋性毒性有关。     

外源性的电磁干预对神经病理性疼痛大鼠的镇痛效果研究

目的:探讨外源性的电磁干预方法对神经病理性疼痛大鼠的镇痛效果。方法:将30只成熟的雄性SD大鼠随机等分成3组:空白对照组(Control),坐骨神经慢性压迫损伤(CCI)组以及坐骨神经慢性压迫损伤协同电磁刺激组(CCI+EMF)。CCI组和CCI+EMF组的20只大鼠建立坐骨神经慢性压迫损伤模型,CCI+EMF组大鼠行外源性的全身性电磁刺激干预(脉冲波形,频率15 Hz,强度30 Gs),每天刺激6小时。在CCI模型构建的第0、3、6、9、12及15天对大鼠测试和比较足底机械痛阈值、足底热痛阈值、运动功能评分和神经传导速率。结果:CCI组大鼠的足底机械痛阈值、足底热痛阈值及感觉神经传导速率从CCI手术后的第3天即出现显著性降低,其6、9、12、15天足底机械痛阈值、足底热痛阈值及感觉神经传导速率均显著低于Control组(P0.01),而运动功能评分均显著高于Control组(P0.05)。CCI+EMF组大鼠的足底机械痛阈值、足底热痛阈值及感觉神经传导速率在第9、12、15天显著高于CCI组大鼠(P0.05),而运动功能评分均显著高于CCI l组。结论:外源性的电磁刺激对于神经病理性疼痛大鼠具有良好的镇痛效果,有望成为一种临床治疗神经病理性疼痛的新的物理治疗手段。     

Mechanism of the suppression of the spinal pain syndrome by serotonin derivatives

The ability of serotonin derivatives to stimulate cAMP accumulation in isolated nerve terminals and lumbar enlargement of the spinal cord of normal rats was compared. The effect of the compounds on the intensity of spinal pain syndrome was also assessed. It has been established that substitutes injected into NH2-group of serotonin in 5-OH position attenuate the ability to stimulate cAMP accumulation in synaptosomes, with the effect more pronounced with substitutes of larger volume. A certain correlation between the ability of serotonin derivatives to stimulate adenylate cyclase in vivo and in vitro, on the one hand, and their analgetic effect, on the other hand, is suggested.     

Protective effect of Vipera raddei venom damage of peripheral nerve

In rats, single pulse activity of inter- and motoneurons of the spinal cord lumbar segment was studied in stimulation of cut. n. ischiadicus, extensor (n. gastrocnemius) and flexor (n. peroneus communis) after treatment with the Viper raddei venom for 4 weeks. In the control rats, no responses occurred in the n. ischiadicus distal stump, whereas the responses to contralateral nerve stimulation did occur. On the intact side, the responses occurred in opposite sequence. The absence of effects of the cut nerve distal stump stimulation in control rats resulted from the coalescence absence in the proximal stump which suggests atrophy of the distal stump. Morphological data prove a distal stump hypertrophy and restoration of the affected limb motor activity. The findings suggest a possibility of application of the Viper raddei venom for regeneration of injured peripheral nerve.     

Subdiaphragmatic vagal afferent nerves modulate visceral pain

Activation of the vagal afferents by noxious gastrointestinal stimuli suggests that vagal afferents may play a complex role in visceral pain processes. The contribution of the vagus nerve to visceral pain remains unresolved. Previous studies reported that patients following chronic vagotomy have lower pain thresholds. The patient with irritable bowel syndrome has been shown alteration of vagal function. We hypothesize that vagal afferent nerves modulate visceral pain. Visceromotor responses (VMR) to graded colorectal distension (CRD) were recorded from the abdominal muscles in conscious rats. Chronic subdiaphragmatic vagus nerve sections induced 470, 106, 51, and 54% increases in VMR to CRD at 20, 40, 60 and 80 mmHg, respectively. Similarly, at light level of anesthesia, topical application of lidocaine to the subdiaphragmatic vagus nerve in rats increased VMR to CRD. Vagal afferent neuronal responses to low or high-intensity electrical vagal stimulation (EVS) of vagal afferent Adelta or C fibers were distinguished by calculating their conduction velocity. Low-intensity EVS of Adelta fibers (40 microA, 20 Hz, 0.5 ms for 30 s) reduced VMR to CRD at 40, 60, and 80 mmHg by 41, 52, and 58%, respectively. In contrast, high-intensity EVS of C fibers (400 microA, 1 Hz, 0.5 ms for 30 s) had no effect on VMR to CRD. In conclusion, we demonstrated that vagal afferent nerves modulate visceral pain. Low-intensity EVS that activates vagal afferent Adelta fibers reduced visceral pain. Thus EVS may potentially have a role in the treatment of chronic visceral pain.     

大鼠脊神经压迫后早期痛阈与神经损伤程度的联系

目的观察大鼠脊神经压迫后早期痛阈改变与神经损伤程度的联系。方法雄性SD大鼠32只,随机分为4组（每组n=8）：正常组,假手术组,70 g压迫组和180 g压迫组。正常组不作任何处理,作为对照,假手术组模型制作过程和其它两个模型组相同,但不做神经压迫,70 g压迫组和180 g压迫组分别用70 g或180 g血管夹压迫大鼠右侧颈7脊神经15 min,制作神经急性压迫损伤模型。于术前2 d和术后1、35、、7 d测右侧前足机械性痛阈和热痛阈,术后7 d处死大鼠取右侧颈7脊神经,HE染色病理分级和扫描电镜观察,比较各组痛阈改变以及神经损伤程度的变化。结果与术前相比较,正常组和假手术组术后机械性痛阈和热痛阈无明显变化（P〉0.05）;与术前以及正常组和假手术组相比,70 g压迫组术后1～7 d机械性痛阈和热痛阈明显降低（P〈0.05）,180 g压迫组术后1 d痛阈无明显变化（P〉0.05）,术后3～7 d明显升高（P〈0.05）。正常组和假手术组均未出现神经损伤病理变化,而70 g压迫组和180g压迫组出现不同程度的神经损伤,损伤病理分级180 g压迫组高于70 g压迫组（P〈0.05）。结论70 g或180 g血管夹压迫大鼠颈7脊神经后大鼠痛阈降低或升高,其机制可能与不同的压力导致不同的神经损伤程度有关。     

人参皂甙Rd通过调节SNI大鼠背根神经节钠、钾电流抑制痛敏

目的:观察人参皂甙Rd(ginsenoside Rd)对大鼠坐骨神经分支选择性损伤(spared sciatic nerve injury,SNI)引起的痛敏的影响及其作用机制。方法:坐骨神经分支选择性损伤术后7天,观察腹腔注射不同浓度人参皂甙Rd后大鼠后足的机械性缩足反应阈值(paw withdrawl mechanical threshold,PWMT)的变化;在术后7天,急性分离并取出大鼠腰4和腰5段背根节,对整节DRG上的中小型神经元运用全细胞膜片钳技术进行记录。结果:坐骨神经分支选择性损伤术后7天,大鼠出现明显的机械性痛敏,腹腔注射5 mg/ml和10 mg/ml的人参皂甙Rd能剂量依赖性的翻转大鼠机械性痛敏;坐骨神经分支选择性损伤能明显地增大SNI大鼠DRG中小型神经元上的钠电流以及减小电压依赖性钾电流,而100μM人参皂甙Rd能有效翻转该钠、钾电流的变化。结论:人参皂甙Rd能有效地改善坐骨神经分支选择性损伤引起的机械性痛敏,其机制可能与人参皂甙Rd明显地调节SNI大鼠DRG中小型神经元上的电压依赖性钠、钾电流有关。     

人参皂甙Rd通过调节SNI大鼠背根神经节钠、钾电流抑制痛敏

目的：观察人参皂甙Rd（ginsenoside Rd）对大鼠坐骨神经分支选择性损伤（spared sciatic nerve injury,SNI）引起的痛敏的影响及其作用机制。方法：坐骨神经分支选择性损伤术后7天,观察腹腔注射不同浓度人参皂甙Rd后大鼠后足的机械性缩足反应阈值（paw withdrawl mechanical threshold,PWMT）的变化;在术后7天,急性分离并取出大鼠腰4和腰5段背根节,对整节DRG上的中小型神经元运用全细胞膜片钳技术进行记录。结果：坐骨神经分支选择性损伤术后7天,大鼠出现明显的机械性痛敏,腹腔注射5 mg/ml和10 mg/ml的人参皂甙Rd能剂量依赖性的翻转大鼠机械性痛敏;坐骨神经分支选择性损伤能明显地增大SNI大鼠DRG中小型神经元上的钠电流以及减小电压依赖性钾电流,而100μM人参皂甙Rd能有效翻转该钠、钾电流的变化。结论：人参皂甙Rd能有效地改善坐骨神经分支选择性损伤引起的机械性痛敏,其机制可能与人参皂甙Rd明显地调节SNI大鼠DRG中小型神经元上的电压依赖性钠、钾电流有关。     

Analysis of spinal cord proteome in the rats with mechanical allodynia after the spinal nerve injury

Proteome analysis was carried out to identify the proteins associated with neuropathic pain after peripheral nerve injury. Five proteins displayed different expression levels among three groups of rats. Among these proteins, creatine kinase B expression level was lower in the pain-positive rats compared to the sham or pain-negative rats. Therefore, a lower creatine kinase B expression level may be important in the development and maintenance of neuropathic pain.     

The potential role of nerve growth factor in cryoneurolysis-induced neuropathic pain in rats

Cryoanalgesia is suggested as a risk factor of neuropathic pain. The current study investigated the pain behavior of sciatic nerve cryoneurolysis (SCN) in adult male rats. The role of nerve growth factor (NGF) was also studied. The mechanical threshold was significantly elevated in SCN group than sham-operation group within 14days after surgery. After 28days, 22 out of 39 SCN rats (56.4%) represented mechanical hyperalgesia. There were much more NGF-immunoreactive nerve cells expressed in the dorsal horn in SCN rats with hyperalgesia. The NGF protein levels of SCN rats measured by Western blot were higher than sham-operation rats, while they were significantly higher in SCN rats with hyperalgesia than those without hyperalgesia. Pain-related behavior improved after anti-NGF treatment, compared with vehicle control group. NGF is associated with SCN-induced neuropathic pain. Peripherally secreted NGF may play an important role in this mechanism.     

慢性神经痛对抑郁状态以及中枢多巴胺神经元电生理的影响

目的：探讨大鼠慢性神经痛导致抑郁症状发生后,中脑腹侧被盖区多巴胺能神经元自发放电活动的改变情况。方法：24只健康成年大鼠进行随机分组（n=12）：假手术组（Sham）大鼠仅进行坐骨神经分支暴露,坐骨神经损伤组（SNI）进行坐骨神经分支选择性损伤。在神经损伤后的第3、7、14、28、42、56天进行机械刺激计算缩足反射阈值,并进行糖水偏好、强迫游泳、旷场实验等行为学实验来评价大鼠是否发生抑郁症状;利用在体多通道电生理技术,对SNI组大鼠和假手术组大鼠中脑腹侧被盖区神经元分别进行记录分析。结果：与假手术组比较,SNI组大鼠的机械痛阈值明显降低（P<0.01）;在旷场实验、糖水偏好、强迫游泳较对照组出现显著性差异（P<0.01）;大鼠中脑腹侧被盖区多巴胺能神经元自发放电频率、簇状放电活动中动作电位的数量明显增加（P<0.01）。结论：慢性疼痛可以导致大鼠抑郁相关症状的发生,中脑腹侧被盖区多巴胺能神经元自发放电频率增加与疼痛后抑郁发生相关。     

Degradation of CCK-8 by rat synaptosomal peptidases

By use of an antiserum raised against conjugated ovine corticotropin releasing factor (CRF_1–41), nerve fibres can be stained immunocytochemically in the external zone of the median eminence of rats. The presence of CRF-immunoreactive (CRF_i) nerve fibres and the plasma corticosterone response to ether stress were studied in rats 6–7 days after making various types of lesions in the hypothalamus. Complete anterolateral deafferentation of the mediobasal hypothalamus caused complete disappearance of CRF_i fibres from the median eminence and blocked the corticosterone response to stress. Incomplete anterolateral hypothalamic deafferentation did not prevent the stress-induced increase of corticosterone and in these rats, part of the CRF_i nerve fibres remained intact. A horizontal cut placed ventral to the paraventricular nuclei, completely prevented the corticosterone response in those rats that showed a complete disappearance of CRF_i nerve fibres from the median eminence. Some rats however, still exhibited CRF_i nerve fibres and these animals responded to stress with increased corticosterone levels. A similar horizontal cut made just dorsal to the paraventricular nuclei affected neither the corticosterone response to stress nor the appearance of CRF_i nerve fibres in the median eminence. We conclude that the presence of CRF_i nerve fibres in the median eminence is a prerequisite for rats to show a pituitary-adrenal response to ether stress and therefore represents the first functional evidence for the role of these hypothalamic CRF_i-neurons.     

miR-202 modulates the progression of neuropathic pain through targeting RAP1A

Neuropathic pain is a somatosensory disorder which is caused by disease or nerve injury that affects the nervous system. microRNAs (miRNAs) are proved to play crucial roles in the development of neuropathic pain. However, the role of miR-202 in neuropathic pain is still unknown. Sprague-Dawley rats were used for constructing the neuropathic pain model. The expression of miR-202 was determined by quantitative real-time polymerase chain reaction. Potential target gene for miR-202 was measured using bioinformatics methods and Western blot analysis. In this study, we used rats to establish a neuropathic pain model and measured the effect of miR-202 in neuropathic pain. We demonstrated that miR-202 expression was downregulated in the spinal dorsal horn of bilateral sciatic nerve chronic constriction injury (bCCI) rat. However, miR-202 expression was not changed in the dorsal root ganglion, hippocampus, and anterior cingulated cortex of bCCI rat. We identified that RAP1A was a direct target gene of miR-202 in the PC12 cell. RAP1A expression was upregulated in the spinal dorsal horn of bCCI rat. Overexpression of miR-202 could improve the pain threshold for bCCI rats in both hindpaws, indicating that miR-202 overexpression could lighten the pain threshold for model rats. Moreover, RAP1A overexpression increased the pain threshold effect of miR-202 overexpression treated bCCI rats, indicating that miR-202 could lighten the pain threshold through inhibiting RAP1A expression. These data suggested that miR-202 acted pivotal roles in the development of neuropathic pain partly through targeting RAP1A gene.