中枢去抑制易化由外周炎症引发大鼠痛敏的机制研究

发布时间：2018-07-29 08:05

【摘要】： 慢性痛是影响最广泛的疾病之一。据估计,在发达国家中约有20%的成年人受到慢性痛的困扰。虽然对急性痛的诊断和治愈目前都很有效,对慢性痛的治疗则远远未达到人们的期望,因此了解慢性痛过程中神经系统是如何作用的就显得尤为迫切。已有的研究表明在慢性痛过程中中枢神经系统中参与痛觉通路的多个脑区的神经元活动增加,突触传递发生变化引起中枢敏化。中枢神经系统痛觉通路的变化是由外周伤害性感受器的输入增多引发,这种变化又导致了参与痛觉信息传递的神经元对外界刺激的反应进一步增强,并且这种增强是一种长时程的变化。研究指出中枢敏化过程中,中枢神经系统的突触传递发生了变化。其中兴奋性突触传递发生了易化,而抑制性突触传递则被抑制。这就提高了兴奋性,使得神经元在接受伤害性刺激时反应增强或是阈下刺激时也会产生反应。成年动物的中枢神经系统中,GABA能突触传递是主要的快速抑制性突触传递。GABA_A受体是一种氯离子通道,神经元胞内外氯离子浓度梯度决定了它的效能。对多种神经疾病的研究表明神经元上氯离子的转运体KCC2功能受到神经元活动的调节,进而改变抑制性突触传递的效能。此外,GABA的合成酶,GABA能的中间神经元以及GABA_A受体也都受到突触活动的调节,并且在神经疾病中它们的表达与功能也发生变化。虽然已有人证明在外周神经损伤引起的慢性痛过程中也存在着抑制性突触传递的降低(去抑制),然而对这种降低的机制研究还不够深入。本研究中,我们利用外周炎症引起的慢性痛成年大鼠模型,对抑制性系统在中枢痛觉通路的多个脑区的变化进行了研究,并探索了调节抑制性突触传递的可能生理意义。 1.慢性炎症痛大鼠脊髓背角KCC2的表达变化与其机制的研究本研究中,我们发现在外周炎症诱发的慢性痛过程中,脊髓背角浅层神经元的KCC2表达明显降低,并且这种降低呈现时间依赖关系,随着慢性痛持续时间的延长,KCC2的表达持续降低。KCC2的表达降低起到了易化痛敏的作用。此外,单侧的外周炎症会引起双侧脊髓背角的KCC2表达降低。我们也证明慢性炎症痛中KCC2的降低依赖于BDNF-TrkB受体信号通路的激活。我们的研究结果提示,在外周炎症诱发的慢性痛过程中脊髓背角也会出现去抑制,KCC2降低易化痛敏的机制可能是减少神经元胞内外的氯离子梯度,降低了抑制性突触传递的效能。而KCC表达降低的时间依赖性则提示其降低可能对慢性痛的维持贡献更大。而KCC2的降低是由BDNF-TrkB受体信号通路的激活所导致的,这也说明KCC2的表达受到神经元活动的调节。 2.前扣带回皮层的去抑制易化了慢性痛中的痛敏的研究本研究中,我们利用全细胞膜片钳的方法首先检测了外周炎症诱发的慢性痛对前扣带皮层Ⅱ,Ⅲ层神经元上兴奋性突触传递的影响。我们发现慢性痛导致了这些神经元的兴奋性输入增多。另一方面,这些神经元接受的抑制性突触传递则发生了显著降低。我们进一步对抑制性突触传递降低的机制进行了探索。通过对mIPSC进行非稳态噪音分析,我们发现在突触传递过程中被激活的GABA_A受体数量减少,同时通过配对刺激记录IPSC,我们发现在慢性痛中抑制性突触的突触前释放机制发生了变化但释放概率没有降低,这就提示我们观察到的抑制性突触传递的降低可能主要是由于突触后受体减少造成的。通过检测GABA_A受体的β2,3亚基在前扣带回皮层的表达我们发现外周炎症诱发的慢性痛降低了GABA_A受体在前扣带回皮层的表达,KCC2的表达也降低。另一方面,负责合成GABA的谷氨酸脱羧酶的表达并没有降低,GAD65的表达反而在慢性痛中上升。此外,外周炎症诱发的慢性痛引起前扣带皮层神经元的输出增加并且我们的结果提示这些神经元对兴奋性输入的整合发生变化。行为学实验则提示,慢性痛中增强前扣带皮层抑制性突触传递可以减缓痛敏。因此,本研究提示,前扣带回皮层的抑制性突触传递的降低易化了慢性痛中痛敏,这种降低是由于GABA_A受体和KCC2的表达降低引起的。而与此同时,前扣带回皮层的抑制性系统也可能存在着稳态调节机制试图弥补受体表达降低导致的抑制性突触传递的削弱。增高的兴奋性与降低的抑制性输入就导致了神经元的输出增加。本工作的创新在于:1)第一次报道了外周炎症诱发的慢性痛会导致KCC2的表达长时程下调,并且这种下调依赖于BDNF-TrkB受体信号途径的激活。这就提示了KCC2表达降低可能是对多种慢性痛的维持起重要作用。2)第一次报道了外周炎症诱发的慢性痛会导致前扣带回皮层抑制性突触传递的降低,这种降低促进了了神经元的输出,易化了痛敏。并且我们也证明在慢性痛中前扣带回皮层抑制性系统存在稳态调节机制。
[Abstract]:Chronic pain is one of the most widely affected diseases. It is estimated that about 20% of adults in developed countries are suffering from chronic pain. Although the diagnosis and cure of acute pain are now very effective and the treatment of chronic pain is far from people's expectations, it is particularly important to know how the nervous system works in the process of chronic pain. The changes in the pain pathway of the central nervous system are caused by the increase in the input of the peripheral nociceptive receptor, which leads to the involvement of the pain in the central nervous system. The synaptic transmission in the central nervous system changes in the central sensitization process. In the central sensitization process, the synaptic transmission in the central nervous system is changed, and the inhibitory synaptic transmission is suppressed. This increases the excitement. Sex makes neurons respond more strongly when they receive nociceptive stimuli or react under subliminal stimuli.
In the central nervous system of adult animals, GABA synaptic transmission is the major fast inhibitory synaptic transmission, the.GABA_A receptor is a chloride channel, and the concentration gradient of the intracellular and external chlorine ion determines its effectiveness. A study of various neural diseases indicates that the function of the transporter KCC2 function of the neurons on the neuron is subjected to neuronal activity. In addition, GABA synthase, GABA intermediate neurons and GABA_A receptors are also regulated by synaptic activity, and their expression and function are also changed in neural diseases. Although it has been shown that there is also inhibition in the process of chronic pain caused by peripheral nerve injury. In this study, we studied the changes in the multiple brain regions of the central pain pathway and explored the possible physiological regulation of the inhibitory synaptic transmission in this study. Significance.
Expression and mechanism of KCC2 in spinal dorsal horn of 1. chronic inflammatory pain rats
In this study, we found that in the process of chronic pain induced by peripheral inflammation, the expression of KCC2 in the superficial neurons of the dorsal horn of the spinal cord decreased significantly, and the decrease presented a time dependence. With the prolonged duration of chronic pain, the expression of KCC2 continued to decrease and the expression of.KCC2 decreased to the role of susceptibility to pain sensitivity. Inflammation may cause a decrease in KCC2 expression in the dorsal horn of the spinal cord. We also demonstrate that the reduction of KCC2 in chronic inflammatory pain depends on the activation of the BDNF-TrkB receptor signaling pathway. Our results suggest that the dorsal horn of the spinal cord also appears depressing during the process of chronic inflammation induced by peripheral inflammation, and the mechanism for reducing the susceptibility to susceptibility to KCC2 may be the reduction of God. The inhibitory synaptic transmission is reduced by the intracellular and extracellular chloride gradient, and the time dependence of the decrease of KCC expression suggests that its reduction may contribute more to the maintenance of chronic pain. The reduction of KCC2 is caused by the activation of the BDNF-TrkB receptor signaling pathway, which also indicates that the expression of KCC2 is regulated by neuronal activity.
2. the inhibition of anterior cingulate cortex facilitates the study of pain sensitivity in chronic pain.
In this study, we used whole cell patch clamp techniques to first detect the effects of chronic pain induced by peripheral inflammation on excitatory synaptic transmission on the neurons in the anterior cingulate cortex II and III neurons. We found that chronic pain leads to increased excitatory input in these neurons. On the other hand, these neurons accept inhibitory synaptic transmission. We further explored the mechanism of the inhibition of inhibition of synaptic transmission. By analyzing the nonstationary noise of mIPSC, we found that the number of activated GABA_A receptors in the synaptic transmission was reduced and the IPSC was recorded by paired stimuli, and we found the presynaptic release of the inhibitory synapse in chronic pain. The release mechanism changes but the release probability does not decrease, which suggests that the decrease of the inhibitory synaptic transmission is probably due to the reduction of postsynaptic receptors. By detecting the expression of the GABA_A receptor's beta 2,3 subunit in the anterior cingulate cortex, we found that the chronic pain induced by peripheral inflammation reduces the GABA_A receptor in the CINgle. The expression of KCC2 in the anterior cingulate cortex was also reduced. On the other hand, the expression of glutamic acid decarboxylase, which was responsible for the synthesis of GABA, did not decrease, and the expression of GAD65 increased in chronic pain. In addition, the chronic pain induced by peripheral inflammation caused the output of the neurons in the anterior cingulate cortex and our results suggest that these neurons are on the rise. This study suggests that the reduction of inhibitory synaptic transmission in the anterior cingulate cortex facilitates the reduction of chronic pain sensitivity, which is caused by a decrease in the expression of GABA_A receptor and KCC2. At the same time, the inhibitory system of the cingulate cortex may also have homeostasis mechanisms that try to compensate for the weakening of the inhibitory synaptic transmission resulting from the decrease in the receptor expression. Increased excitability and reduced inhibitory inputs lead to an increase in the output of neurons.
The innovations in this work are as follows: 1) the first report of chronic pain induced by peripheral inflammation leads to a long time downregulation of the expression of KCC2, and this downregulation depends on the activation of the BDNF-TrkB receptor signaling pathway. This suggests that the decrease of KCC2 expression may be an important role in the maintenance of multiple chronic pain.2) the first report of peripheral inflammation Chronic pain leads to a decrease in the inhibitory synaptic transmission of the anterior cingulate cortex, which promotes the output of neurons and facilitates pain sensitivity. And we have also demonstrated that there is a steady regulation mechanism in the cingulate cortex suppressor system in chronic pain.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2008
【分类号】：R363

【引证文献】