【作者】 张玲；

【导师】 赵志奇；

【作者基本信息】 复旦大学 ， 神经生物学， 2005， 博士

【摘要】 疼痛是一种与组织损伤或潜在的损伤相关的不愉快的主观感觉和情绪体验。它包括两方面的含义：痛的感觉分辨和情绪反应。疼痛是多种疾病伴随的共同症状，尤其是慢性痛，常常严重地影响着人类的身心健康，降低了患者的生活质量，因此研究疼痛产生的机制、进而找到解决临床疼痛问题的最佳途径就显得尤为重要。 众所周知，疼痛的初级感觉中枢——脊髓的痛觉信息可以受到多种因素调节。数十年来，中枢神经系统内源性痛觉调制系统的发现成为痛觉研究中进展最为突出的领域之一。脊髓上中枢对脊髓痛觉的调制呈现双向性，即下行抑制和下行易化。而下行易化调节在病理性痛的产生和维持中起着关键性的作用。 前扣带皮层(anterior cingualte cortex，ACC)是边缘系统的重要结构。由于它是既接受来自皮层下多种信息的传入又可恒定地被外周伤害性刺激所激活的高级皮层，近年来已成为疼痛研究的热点区域。研究表明ACC不仅调节痛的感觉还参与痛情绪的形成。但是值得提出的问题是：ACC可接受并整合传入的各种信息，尤其是外周持续伤害性刺激的传入可以使ACC本身产生可塑性变化，但是ACC怎样将信号输出、如何对疼痛进行调节是目前我们知之甚少的领域。 本研究采用电生理和行为学的方法探讨ACC对脊髓伤害性信息传递的调节和对丘脑中央外侧核痛兴奋神经元的影响，主要结果如下： 1．以0.2ms、100Hz、5s一次60μA的强直性电刺激一侧ACC 2.5min，可使C纤维诱发的脊髓场电位长时程增强，平均增加145．77±1.86％，并可以维持2h以上；同样的刺激对A纤维诱发的场电位没有影响。采用60和600uA两种强度的单个刺激均不能引起C纤维诱发场电位的长时程增强。 2．强直性电刺激一侧ACC使双侧辐射热引发的抬腿反射长时程增强，大鼠左右侧的抬腿反射潜伏期(Paw withdrawal latencies，PWLs)在30min时显著性降低，1-4h达到最高峰，24h以后恢复到对照水平。3．一侧ACC微量注射NMDA受体的选择性激动剂NMDA(1.0μl，10nM)和谷氨酸的替代物HCA(1.0μl，0.1M)均可显著增强大鼠双侧的抬腿反射。 4．NO供体L-Arg(1.0μl，10mM)微量注射一侧的ACC可以长时程的增强脊髓C纤维诱发的场电位，并可以缩短大鼠抬腿反射潜伏期。 5．将单极钨丝电极通以200-500μA的阳极电流10-20s电解损毁双侧延髓背侧网状核(dorsal reticular nucleus，DRt)，然后强直电刺激ACC，由C纤维诱发的场电位几乎没有变化，平均达到对照值的104.01±0.53％；同样电解损毁双侧DRt，由ACC介导的双侧抬腿反射的增强作用也被显著抑制。 6．以波宽0.2ms、频率200Hz、强度60-100μA方波刺激ACC 2s，大部分的CL痛兴奋神经元自发放电增加(50％)，少部分出现自发放电减少(19.2％)或不变(30.8％)。刺激ACC后CL的有些神经元自发放电并不增加，但是感受野在刺激结束后显著增大或神经元性质及放电形式发生改变。如本来对触觉(刷毛)不敏感的细胞，刺激后刷毛引起放电增加；神经元由单个规律的放电变为成簇(burst)放电。 7．电刺激ACC对丘脑中央外侧核(central lateral，CL)的痛兴奋神经元的诱发放电也产生影响。大部分神经元诱发放电增加(56.2％)，少部分神经元出现诱发放电减少(12.5％)或不变(31.3％)。有些细胞在刺激ACC后，诱发放电增加的同时放电形式也发生改变，由原来的单个放电变为成簇(burst)放电。 8．采用荧光染料荧光金(fluorogold，FG)和荧光素(fastblue，FB)逆行束路追踪技术研究ACC向CL的投射。将3％的FG或FB注入大鼠的CL，7天后进行灌注和全脑切片，将片厚40μm的切片贴于载玻片在荧光显微镜下观察。 结果显示：双侧ACC有大量的强荧光标记的阳性神经元，同侧多于对侧。此外，在屏状核(claustrum，Cl)及下丘脑亦有少量阳性神经元。 以上结果表明：ACC对脊髓伤害性感觉具有易化作用；DRt介导ACC对脊髓伤害性信息的下行易化调节；ACC对CL痛兴奋神经元的自发放电和诱发放电主要产生兴奋性作用；CL接受双侧ACC纤维投射；提示对ACC对疼痛的调节也可以发生在间脑水平。更多还原

【Abstract】 Pain, an unpleasant sensory and emotional experience, is associated with actual or potential tissue damage, which includes a sensory-discriminative and an affective-motivational component. Meanwhile, it is usually a common symptom of many diseases. Especially, chronic pain has an severe effect on people physically and psychologically, and impairs quality of life of human being markedly. Therefore, revealling the underlying mechanism of pain and eventually finding a solution to relief of pain seems very important today.As well known, the spinal nociception, primary sense center of pain ,can be modulated by several factors. The research on endogenetic pain modulation from central nerve system have developed rapidly and already become one of the most prominent fields in the late decades. The studies show that supraspinal center biphasically modulate spinal nociceptive transmission: descending inhibition and facilitation. As indicated by recent research, descending facilitatory modulation is probably a key mechanism for occurrence and maintenance of neuropathic and inflammatory pain.Anterior cingulate cortex (ACC) is an important part of the limbic system and the high-level center of brain, which not only receives all kinds of information from subcortex, but also is reliably activated by peripheral noxious stimulus, and has been a hotspot of pain exploration. Though the adequate data has already been collected about the ACC modulation of sensatory and emotional component of pain, the studies were almost confined to the aspect : how the ACC receive nociceptive information. The research on how the ACC transmits nociceptive information and how it regulates spinal nociception has been little conducted so far. So here a question comes out: how the ACC modulate the pain in top-down manner and in which way does the ACC is connected to the subcortex nuclei.The present study was designed to investigate how the ACC modulate the spinal nociception and it affect the activation of the central lateral nuclei of intralaminar nuclear by means of electrophysiology and behavior test. The result is as following:1. C-fiber-evoked potentials were significantly enhanced by 145.77 ± 1.86 % of control following unilaterally electrical stimulation of the ACC (60 μA, 0.2 ms, 100 Hz for 1 sec, interval 5 sec, for 2.5 min), and lasted for more than 2 h. Meanwhile the A-fiber-evoked potentials were not affected by the same stimulation. Two kind of intensity(60 and 600μA) regular electrical stimulation of the ACC didn’t long lasting enhanced the C-fiber-evoked potentials.2. One week after surgery, PWLs to noxious heating were measured and compared before and after ACC stimulation. The electrical stimulation of the unilateral ACC significantly reduced bilateral PWLs. Shortened bilaterally PWLs appeared 30 min after ceasing stimulation of the ACC, which reached the peak after 1-4 hours and recovery after 24hours.3. One week after implanting microinjection cannula, NMDA( 1.0μl, 10nM) and homocysteic acid (HCA) (1.0μl, 0.1M) was microinjected into the ACC unilaterally, the PWLs were significantly shortened bilaterally.4. Microinjection of L-Arg (1μl 10mM ) , the donor of NO, the C-fiber-evoked potentials and paw withdrawal response significantly enhanced.5. Following the bilateral dorsal reticular nuclei (DRt) were electrolytically lesioned (anodal DC current 200-500 μA, 10-20s), ACC stimulation-induced facilitation of C-fiber-evoked field potentials and paw withdrawal respond was markedly diminished.6. After electrical stimulation of the ACC (60-100 μA, 0.2 ms, 200 Hz, interval 10 sec, for 2s), the spontateous discharge of nociceptive neuronsin the CL was recorded. The results showed most (50%)of them were excited, the rest of 19.2% and 30.8% showed inhibitory and unchanged respectively. In spite of the spontaneous discharge of some neurons didn’t change, they alterate their receptive field, the character of neurons and the pattern of discharge after stimulation of the ACC.7. The evoked discharge of nociceptive neurons in th CL was also changed after stimulation of the ACC. The results showed most (56.2%)of them were excited, the rest of 12.5% and 31.3% showed inhibitory and unchanged respectively. Following increased of their evoked discharge some neurons also changed their pattern of discharge from single to burst after stimulation of the cortex.8. Using fluorogold (FG) and fastblue (FB) retrograde tract-tracing technique, the afferent projection of the CL from ACC was traced. FG and FB (3%, 1.0μl) were injected into unilateral CL. Seven days later, the rats were perfused. Forty-micrometer-thick sections were mounted on slides and observed under microscopy. The results showed that the ACC project strongly to CL bilaterally. Ipsilateral has more neurons than the contralateral of the ACC. In addition to the ACC, the claustrum(CI) and the hypothalamus also project a mall quatity neurons to the CL.In conclusion, the ACC is believed to facilitate the spinal nociception in descending mode; DRt contributes to the ACC-induced descending facilitation; The ACC not only has a lot of neurons project to the CL but also can facilitate the spontaneous and evoked discharge of the nociceptive neurons in the CL. All the above suggest that the ACC modulate the pain at the level of spinal and diencephalons更多还原