论文标题:去甲肾上腺素对受损背根节神经元持续性钠流的作用
The Study of Effect for Norepinephrine on Persistent Sodium Current in Injured DRG Neurons
论文作者 刘志洋
论文导师 胡三觉；王玉英,论文学位 硕士,论文专业 神经生物学
论文单位 第四军医大学,点击次数 85,论文页数 57页File Size1844k
2005-04-01论文网 http://www.lw23.com/lunwen_48919492/ 背根节;神经元;去甲肾上腺素;阈下膜电位振荡;持续性钠流;TTX;膜片钳
dorsal root ganglia; neuron; norepinephrine; subthreshold membrane potential oscillation; persistent sodium current;TTX ; patch clamp
机械性外伤、缺血、局部炎症等各种致病因素可直接或间接引起外周神经的损伤,诱发以痛觉过敏、痛性感觉异常、自发性疼痛为主要表现的持久异常痛感觉,称为慢性痛。由椎间盘脱出以及椎间孔狭窄等引起的背根神经节(dorsal root ganglia,DRG)或脊神经根受压导致的疼痛是临床常见的慢性痛症状。此时作为感觉传递第一站的DRG受损神经元的兴奋性往往异常增高,呈现超兴奋状态。这种神经元超兴奋主要表现为阈值降低,适应性减弱,自发放电等变化,并成为产生慢性神经病痛的“起搏点”。这种异位自发放电产生的基础是阈下膜电位振荡(subthreshold membrane potential oscillation,SMPO)。同时,在组织炎症和周围神经损伤后,感觉神经元和外周感受器表现对去甲肾上腺素(norepinephrine,NE)受体激动剂和交感传出纤维兴奋异常敏感。在体加入NE对这种异位自发放电的产生有一定的促进作用。并且证明了是SMPO介导NE对损伤DRG神经元的兴奋性作用。然而,NE影响SMPO的离子通道机制尚不清楚,制约着慢性病痛机制的进一步研究。 本研究利用大鼠背根节慢性压迫造成的神经元超兴奋标本,通过离体单细胞膜片钳记录技术对受损DRG神经元电生理检测,阐明NE对SMPO影响的离子通道机制,有助于深入揭示慢性痛“起搏点”形成的原因,为慢性痛治疗提供新的策略。
Peripheral nerve injury induced by mechanical trauma,ischemia,or local inflammation can lead to chronic pain symptoms,including hyperalgesia,allodynia,spontaneous pain. The sciatic nerve and low back pain are often ascribed to chronic compression of the dorsal root ganglia(DRG) or its spinal root by herniated intervertebral disc,or stenosis of intervertebral foramen.In this case,the excitability of injured neurons within DRG,which is considered as the first stage of the sensory pathway,enhance abnormally,,and those neurons become hyperexcitable.Experiments have documented a variety of changes occurring in injured hyperexcitable neurons,comprising of reduction of the spike rheobase,accommodation, initiation of spontaneous discharges.Thus injured DRG neurons become the pacemaker of neuropathic pain.Subthreshold membrane potential oscillation(SMPO) is the foundment for producing ectopic spontaneons discharges.Then,sensory neurons and nociceptors may develop abnormal responsiveness to sympathetic agonists and the activation of postganglionic sympathetic efferent axons in certain neuropathic pain state after tissue inflammation and nerve lesion.Norepinephrine(NE) have certain enhancement effect on this ectopic spontaneous discharges in intro and subthreshold membrane potential oscillation mediates the exciatory effect of norepinephrine in chronically compressed dorsal root ganglion neurons in the rat. however, the ion channelmechanism is still not very clear for norepinephrine contributing on SMPO,limiting the further study of mechanism for the chronic pain.To utilize the hyperexcitable speciments in the neurons of chronically compressed DRG. Through electrophysiological detection for whole-cell pach clamp of single cell in injured DRG neurons in intro, we aim to elucidate the ion mechanism of NE contributing on SMPO.This will help to make clear of the reason of why the pacemaker of chronic pain formed. So can supply a new therapy strategy for chornic pain.Experiment results 1 .Detection of the persistent sodium current(I_(Nap)) in injured DRG neuronsAccording to the biological features of persistent sodium channel:(1) activation potential is lower than the transient sodium channel ,about 10— 15mV negative to the transient sodium current.(2) the time of the channel activation is longer, that is inactivation course is slow. (3) as the channel opening,the amplitude of the current is lower. (4) the high sensitive to TTX. A total of 106 neurons from 48 chronic compressed DRGs were recorded, there are 10 (D>40um) big cells and 85 the middle size cells(D=30~40um) and 11 the small cells(25~30um) between them. After blest sealed in patch-clamp, stimulus in ramp wave (from -80mV to -30mV, time 3s), recording in perforated whole-cell pach clamp. The current is different according to the cell size,the big cells have the bigger current. The activation potential of middle size cells is about -70mV, and the most biggest current showed at -55 mV, the averge amplitude is 150±40 pA.The opening time is almost alike, the middle cell is 180±20 ms,the small is 165±15 ms,the averge time is 150—200 ms. 2.The persistent current is sensitive to TTXThe detected persistent current is high sensitive to the low concentration TTX in injured DRG neurons. Usually at 100 nmol/L concentration may be blocked wholey.This illusted that it is a new persistent sodium curret different
|
