DIFFUSION OF SUBSTANCES THROUGH THE BRAIN

描述本项目将描述和量化 脑细胞外微环境中的分子。结果将会是 也揭示了细胞外空间的几何形状和物质是如何 被摄取过程去除的。 这项工作将使用微吸管作为点源，将分子释放到 通过离子导入、压力脉冲或受控输液对大脑进行治疗。这个 随后的分子分布将使用以下方法测量 离子选择微电极(用于四甲铵和钾) 扫描循环伏安法(用于多巴胺)和集成光学成像(用于 荧光右旋糖苷和白蛋白)。将在大鼠身上进行实验 大脑皮层切片、离体龟小脑和麻醉青蛙。 具体目标有三个： 1)分析边界元的结构特性。这将寻求 发现是否某些区域无法被大分子访问，但无法访问 小分子和透明质酸盐或类似分子都会阻碍扩散。 其他实验将探索从扩散流到整体流的转变。 当分子以更快的速度注入大脑时 调查是否有证据表明大脑中存在内源性大流量。 2)比较多巴胺的区域摄取动力学和扩散。使用 含Michaelis Menten摄取动力学的扩散方程推广到 解释数据，多巴胺在纹状体，伏隔核， 将对黑质和腹侧被盖区进行研究。摄取 阻滞剂将被用来进一步表征动力学性质。 3)量化空间缓冲对钾的贡献 动态平衡。扩散方程将被扩展以适应空间 根据Gardner-Medwin和点源的方法进行缓冲 将使用范例来确定空间缓冲区对 不同条件下生物膜对钾的去除效果。阻滞剂 负责空间缓冲的内向整流通道 将测试缝隙连接的作用。进一步的实验将调查 钾动态平衡的其他机制，如KCl2吸收。 这项研究与细胞间的非突触通讯有关。 对扩散化学信使的作用的表征 发展中的扩散因素，多巴胺替代疗法 减轻帕金森氏症，预防钾诱导的细胞损伤 以及制定药物输送到大脑的策略。

DESCRIPTION This project will characterize and quantify the diffusion of molecules in brain extracellular microenvironment (BEM). The results will also reveal the geometry of the extracellular space and how substances are removed by uptake processes. The work will use a micropipette as a point-source to release molecules into the brain by iontophoresis, a pressure pulse or a controlled infusion. The subsequent distribution of the molecules will be measured using ion-selective microelectrodes (for tetramethylammonium and potassium), fast scan cyclic voltammetry (for dopamine) and integrative optical imaging (for fluorescent dextrans and albumins). Experiments will be made on the rat cortical slice, the isolated turtle cerebellum and the anesthetized frog. There are 3 specific aims: 1) To analyze the structural properties of the BEM. This will seek to discover if some regions are inaccessible to large molecules but not to small ones and whether hyaluronate or similar molecules impede diffusion. Other experiments will explore the transition from diffusion to bulk flow when molecules are infused into the brain at increasing rates and investigate whether there is evidence for endogenous bulk flow in the brain. 2) To compare regional uptake kinetics and diffusion of dopamine. Using an extension of the diffusion equation with Michaelis Menten uptake kinetics to interpret the data, dopamine diffusion in the striatum, nucleus accumbens, substantia nigra and ventral tegmental area will be studied. Uptake blockers will be used to further characterize the kinetic properties. 3) To quantify the contribution of spatial buffering to potassium homeostasis. The diffusion equation will be extended to accommodate spatial buffering according to the methods of Gardner-Medwin and the point source paradigm will be used to determine the contribution of the spatial buffer to removal of potassium from the BEM under different conditions. Blockers of the inward rectifier channels responsible for the spatial buffer and the role of gap junctions will be tested. Further experiments will investigate other mechanisms for potassium homeostasis such as KCl uptake. This study is relevant to nonsynaptic communication between cells by means of diffusing chemical messengers, the characterization of the role of diffusible factors in development, dopamine replacement therapies to alleviate Parkinson's disease, prevention of potassium-induced cell damage and the formulation of strategies for drug delivery to the brain.