Electrochemical tools to measure local cerebral blood flow and metabolism

描述（由申请人提供）：测量局部脑血流量和代谢的电化学工具人脑占体重的2%，但消耗总能量的20%来支持大脑中的电活动。为了满足这一需求，脑血流量（CBF）与能量使用的变化相结合。主要有两个控制点。靠近脑表面的血管根据生理需要将血压维持在一个相对恒定的范围内。脑血流在脑组织内的实质内微血管水平上也受到局部调节，这是本研究的主题。脑组织内微血管间隔约505m，与平滑肌相关，允许它们收缩和扩张，这一过程称为功能性充血。控制毛细血管直径的化学信号主要来自星形胶质细胞，即血管周围和突触周围的神经胶质细胞。神经活动激活星形胶质细胞，反过来，星形胶质细胞分泌物质，触发局部毛细血管舒张。在这里，我们建议测试5-羟色胺（5-HT）在大脑区域中高含量存在的CBF中的作用。5-羟色胺是一种有效的血管收缩剂，其终末与小动脉和毛细血管相邻，提示其可直接作用于血管或通过激活星形胶质细胞间接作用于血管。这些作用很重要，因为它们被认为与偏头痛和婴儿猝死综合症有关，也有助于在功能性磁共振成像中观察到的信号。我的实验室已经开发了几种基于电化学的技术，用于体内测量神经递质以及由CBF控制的物种，如O2和ph。本提案有4个具体目标。1. 我们将基于氢气清除技术制备一种CBF电化学探针。这是必要的，因为细胞外氧的浓度等于CBF输送的量减去正在进行的代谢消耗的量。虽然细胞外氧很容易用微电极测量，但要充分表征功能性充血，需要一种测量CBF的方法。2. 我们将检验5-羟色胺在控制特定脑区血流中发挥独特作用的假设。我们的主要目标是黑质，网状部，这是大脑中富含5-羟色胺的区域。3. 我们将测试伏隔核核心（NAc）的细胞外氧在基于奖励的活动中波动的假设。在自由运动大鼠进行颅内自我刺激的同时，监测氧和生物胺类神经递质。4. 我们将检验ICSS期间黑质胞外氧变化的假设。该区域包含多巴胺神经元的树突，并参与运动活动的调节。在ICSS过程中，我们将使用同一电极对该区域的gaba能神经元进行O2和5-HT的化学测量和电生理测量。

DESCRIPTION (provided by applicant): Electrochemical tools to measure local cerebral blood flow and metabolism The human brain comprises 2% of body weight and yet consumes 20% of the total energy to support the electrical activity in the brain. To meet this demand, cerebral blood flow (CBF) is coupled to changes in energy use. There are two primary control points. Blood vessels near the brain surface maintain blood pressure in a relatively constant range according to the physiological requirements. CBF is also locally regulated within brain tissue at the level of the intraparenchymal microvessels, the subject of the proposed research. Microvessels spaced approximately 50 5m apart within brain tissue, are associated with smooth muscles that allow them to constrict and dilate, a process termed functional hyperemia. The chemical signaling that controls the capillaries' diameter primarily originates from astrocytes, glial cells that surround the blood vessels and also surround synapses. Neural activity activates astrocytes, which, in turn, secrete substances that trigger local vasodilation of capillaries. Here, we propose to test the role of serotonin (5-HT) on CBF in brain regions where it is present in high amounts. 5-HT is a potent vasoconstrictor, and its terminals are adjacent to arterioles and capillaries suggesting it can exert action directly on blood vessels or indirectly by activation of astrocytes. These actions are of importance because they have been suggested to be involved in migraine headaches and sudden infant death syndrome, and also to contribute to the signals observed in functional magnetic resonance imaging. My laboratory has developed several electrochemically based techniques for in vivo measurements of neurotransmitters as well as species governed by CBF such as O2 and pH. This proposal has 4 specific aims. 1. We will microfabricate an electrochemical probe of CBF based on the hydrogen clearance technique. This is necessary because the concentration of extracellular O2 is equal to the amount delivered by CBF less the amount consumed by ongoing metabolism. While extracellular O2 is readily measured with microelectrodes, to fully characterize functional hyperemia, a method to measure CBF is required. 2. We will test the hypothesis that 5-HT plays a unique role in the control of blood flow in select brain regions. Our primary target will be the substantia nigra, pars reticulata, a brain region with high 5-HT. 3. We will test the hypothesis that extracellular O2 in the nucleus accumbens core (NAc) fluctuates during reward based activity. Measurements will be made in the freely moving rats during intracranial self-stimulation while monitoring oxygen and biogenic amine neurotransmitters. 4. We will test the hypothesis that extracellular O2 changes in the substantia nigra during ICSS. This region contains the dendrites of dopamine neurons and is involved in the regulation of locomotor activity. We will make chemical measurements of O2 and 5-HT and electrophysiological measurements of GABAergic neurons in this region with the same electrode during ICSS. PUBLIC HEALTH RELEVANCE: Project Narrative: New devices employing electrochemical principles will be devised to measure blood flow in the brain as well as extracellular oxygen levels. These tools will be used to monitor oxygen regulation during reward based behaviors.