以神經病變痛之小鼠模式研究止痛神經迴路

Investigation of pain-relief circuits in a mouse model of neuropathic pain

王仁德(Jen-Te Wang)

指導教授 ： 姚皓傑

國立臺灣大學/醫學院/腦與心智科學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201904070

摘要

本研究旨於使用小鼠作為模式生物，研究慢性神經病變痛在大腦內的神經機轉，透過早期立即基因 c-Fos 的免疫染色，可以當作神經活動的生物標記，發現有神經病變痛的小鼠在前扣帶迴皮質的吻端，有較多的 c-Fos 表現。為了解此神經活動與神經病變痛的因果關係，本研究採用光遺傳學的方法抑制吻端前扣帶迴皮質的神經細胞活動，發現可以有效紓緩機械性輕觸痛。進一步地，本研究欲探討是否有前扣帶迴皮質相關的神經迴路負責調節此止痛效果，於是再次使用c-Fos 免疫染色的方式，篩選參與在止痛歷程中的前扣帶迴皮質傳出腦區，並挑選 zona incerta 及導水管周圍灰質作為兩條探討的迴路。透過光遺傳學方法抑制投射到 zona incerta 的前扣帶迴皮質細胞以及投射到導水管周圍灰質的前扣帶迴皮質細胞，都可以再現於前扣帶迴皮質細胞操弄所看到的行為結果，顯示這兩個下游腦區都有可能參與在前扣帶迴皮質相關的止痛歷程中。最後，為探討本研究發現對於小鼠神經病變痛的止痛效果是否具有酬賞性，光刺激自我注射模範以及制約場域偏好被用來檢驗這個問題，而發現本研究找到的所有止痛效果，都不具有酬賞性。

關鍵字

神經病變痛 ； 光遺傳學 ； 前扣帶迴皮質 ； 導水管周圍灰質 ； 光刺激自我注射模範 ； 制約場域偏好

並列摘要

Previous human neuroimaging and rodent studies have shown that the anterior cingulate cortex (ACC) is a critical brain region in the pain matrix involved in pain processing. Accumulating evidence from rodent studies has suggested that the development of chronic pain results in synaptic reorganization of ACC. In my study, I first adopted spared nerve injury (SNI) as an animal model of neuropathic chronic pain and combined with the activity-dependent c-Fos immunostaining to identify forebrain regions involved in pain representation. After sieving out aACC as potential pain representer, I causally examined the functional roles of the aACC in neuropathic pain by using Halorhodopsin (Halo 3.0) as an inhibitory manipulation tool. I have discovered that one hour of photoinhibition can result in long-lasting relief of mechanical allodynia. To further investigate the circuits underpinnings, I employed similar c-Fos staining strategy to search for pathways mediating painrelief in a mouse model of neuropathic pain. Finally, based on the c-Fos mapping results, I causally examined two subpopulations of aACC neurons, zona incerta-projecting aACC neurons and periaqueductal grey (PAG)-projecting aACC neurons. The results showed that photoinhibition of both circuits can alleviate mechanical allodynia. Moreover, I found that all the analgesia effects in this study were not rewarding, shown by optical intracranial self-stimulation paradigm and conditioned place preference assay. With all of the evidence, I have provided a potential clinical therapy target for resolving maladaptive symptoms of neuropathic pain without inducing addiction side effect, which is commonly accompanied by using of opioid analgesics.

並列關鍵字

neuropathic pain ； optogenetics ； anterior cingulate cortex ； zona incerta ； periaqueductal grey ； conditioned place preference ； optic self-administration

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