脊髓损伤排便功能重建后脑功能重塑的实验研究

Thoracolumbar fracture was common in clinic, which might induce to the disorders of urination and defecation. The disorder of defecation might mainly manifest severe fecal incontinence and chronic intractable constipation. Funded by the National Natural Science Foundation of China (Grant No.30901507), the primary motor and sensory centers were located in rats firstly. Then the repairments of motor and sensory pathways in the rectum and anal canal were performed simultaneously with nerves tranferring. Thus the defecation reflex was established. However, the functional reorganization in rat brain after reconstructed with the new physiological reflex pathway is not yet clear. Therefore, the outcome of functional reorganization will be testified with inter-synaptic retrograde nerve tracing, micro-electrode stimulation and functional magnetic resonance imaging (f MRI), 18F-FDG PET imaging. Thus the functional reorganization changes in the defecation senior center (which included paracentral lobule, hypothalamus and brain- stem) were detected. mRNA and protein expression of brain-derived neurotrophic factor (BDNF), growth associated protein 43 (of GAP43) , non-receptor tyrosine kinase (Fyn) and Trk tyrosine kinase B (TrkB) in the functional areas were measured, which might explore the molecular mechanisms of brain functional reorganization. And this study might offer an experimental foundation to achieve autonomic defecation for the patients after spinal cord injury.

脊柱胸腰段骨折在临床上最为常见，损伤后可导致排尿、排便功能障碍。其肠道症状主要表现为严重大便失禁，慢性顽固性便秘等。本课题组前期在国家自然基金青年项目（30901507）的资助下，首先定位大鼠排便的初级运动、感觉中枢；应用神经移位同时修复直肠与肛管的运动、感觉神经，从而建立了生理排便反射通路。但是新的反射通路能否与大脑中枢建立联系尚不明确。因此，本研究拟以大鼠为研究对象，通过跨突触逆行示踪、微电极刺激、功能磁共振成像、PET显像等方法，来观测排便高级中枢- - 旁中央小叶，丘脑下部及脑干在人工反射通路修复前后的迁移变化规律，并通过测定脑源性神经生长因子（BDNF）、生长相关蛋白43（GAP43）、非受体酪氨酸激酶(Fyn)和Trk酪氨酸激酶B(TrkB) mRNA 及其蛋白在相关脑功能区的表达，从而探讨人工反射通路修复术后大脑重塑的分子机制，可望为临床上脊髓损伤患者实现自主排便奠定实验基础。

脊髓损伤后往往造成排尿及排便功能障碍。随着对泌尿系处理方法的进步，使肠道功能障碍的影响日益突出。在临床上，脊柱胸腰段骨折最常见，损伤后造成脊髓圆锥损伤，其肠道症状主要表现为严重大便失禁，慢性顽固性便秘等。鉴于此，本研究以SD大鼠为研究对象，首先定位了大鼠排便功能最大效应神经根为S1神经根，同时初步定位SD大鼠高级排便中枢为中央脑水管周围灰质区域（PAG区）；并在此基础上成功建立了大鼠排便生理反射弧的动物模型，即将L6前、后根分别与S1前、后根端端吻合修复重建直肠与肛管的运动、感觉神经通路；术后对动物模型有效行进行分析并在此基础上对动物模型术后各时期进行脑重塑监测，动态观察脑重塑过程及相关神经递质分子的变化情况。术后3月通过甲苯胺蓝和电镜等形态学观察，PRV逆行示踪和电生理等功能学检查。结果表明，神经根吻合口形态良好并伴有新生的神经纤维，PRV逆行示踪可很好的跨越吻合口逆行上传，电生理监测显示肛管直肠有部分功能恢复。对模型鼠术后1月、6月及12月分别进行fMRI及微电极刺激动态监测脑重塑变化过程，同时提取相关脑核团进行神经递质测定；结果表明术后1月出现了明显的排便中枢抑制现象，术后6月排便中枢又对排便功能出现了部分再支配现象，而在术后12月对模型鼠脑部相应的区域又由抑制变为去抑制；脑部神经递质BDNF从术后1月、术后3月、术后6月呈现出逐渐升高的趋势并于术后6月达最高峰， 术后12月恢复到基线，而Fyn在术后1月、术后3月、术后6月呈现逐渐下降的趋势并于术后6月达最低峰，于术后12月恢复到基线。总之，本研究探讨了生理排便反射通路的修复效果，并从脑重塑过程和神经递质阐述了可能机制，从而为临床SCI患者排便功能重建提供了新的修复思路。