Optical and fMRI Studies of Cocaine in the Rat Brain

描述（由申请人提供）：本申请描述了一个系统的5年培训计划和实验研究，这将导致在翻译神经科学的独立职业生涯，重点是兴奋剂，如可卡因对大脑的影响。定量光学荧光和光谱成像结合高分辨率磁共振成像（9.4T）将用于计划的研究。在先前的工作中，候选人已经开发了基于导管的光学扩散和荧光（ODF）仪器，其已经被验证用于同时检测缺血期间脑血容量（CBV）、组织氧合（StO 2）和细胞内钙[Ca++]i）的变化（Du等人，J Cereb Blood Flow Metab.，2005（25），1078- 1092）。该系统的初步结果已经获得，其中可卡因-幼稚的大鼠，并与可卡因的自我管理的历史，大鼠进行了比较后，急性可卡因的挑战。在药物初治大鼠中，可卡因诱导CBV和StO 2轻度、一过性降低，[Ca++]i逐渐增加10%。在长期暴露于可卡因的大鼠中，可卡因使[Ca++]i快速增加>20%，CBV和StO 2显著持续降低。此外，在未用药大鼠中，可卡因诱导的[Ca++]i增加与其对CBV和StO 2的作用无关。可卡因诱导的过度[Ca++]i增加（如在自我施用可卡因的大鼠中观察到的）将使细胞更容易受到损伤，特别是当同时伴随CBV和StO 2的降低时（Du等人，提交至J. Neuroscience，2006）。在这里，我们提出了一个策略，分离出直接影响可卡因对血管系统的皮质功能的直接影响。具体目标是：（1）急性可卡因对血流动力学和钙瞬变的影响的表征;（2）测量可卡因对MRI表观扩散系数的影响以确定是否存在细胞损伤，以及在可卡因自我给药和可卡因未处理的大鼠中测量前爪刺激的影响以确定是否存在对皮质功能的影响，（3）评价可卡因戒断对自我给药动物的影响，作为药物戒断期间发生的生理变化的模型，以及（4）对ODF系统进行技术改进，将光学探针的尺寸（目前为3 mm）减小到300 μ m。这第四个目标应该允许在未来的研究中测量来自更深大脑区域的神经信号。PI正在寻求这个K25奖，以进一步扩展她对大脑对滥用药物的急性和慢性给药反应的生理学，生物化学和药理学知识。

DESCRIPTION (provided by applicant): This application describes a systematic 5-year training plan and experimental studies that will lead to an independent career in translational neuroscience with a focus on the effects of stimulants such as cocaine on the brain. Quantitative optical fluorescence and spectroscopic imaging combined with high-resolution magnetic resonance imaging (9.4T) will be used in the planned research. In previous work, the candidate has developed a catheter-based optical diffusion and fluorescence (ODF) instrument, which has been validated for simultaneously detecting changes in cerebral blood volume (CBV), tissue oxygenation (StO2) and intracellular calcium [Ca++]i) during ischemia (Du et al. J Cereb Blood Flow Metab., 2005(25), 1078- 1092). Preliminary results with this system have been obtained in which cocaine-naive rats, and rats with a history of self-administration of cocaine, are compared after an acute cocaine challenge. In drug-naive rats cocaine induced a mild, transient decrease in CBV and StO2 and a gradual 10% increase in [Ca++]i. In chronically cocaine exposed rats, cocaine produced a rapid >20% increase in [Ca++]i and significant, persistent decreases in CBV and StO2. Furthermore in drug naive rats have cocaine-induced increases in [Ca++]i occur independent of its actions on CBV and StO2. Cocaine-induced excessive [Ca++]i increases (as observed in rats self-administering cocaine) would make cells more vulnerable to injury particularly when simultaneously coupled with decreases in CBV and StO2 (Du et a/., submitted to J. Neuroscience, 2006). Here we propose a strategy to separate out direct effects of cocaine on the vasculature from direct effects on cortical function. Specific aims are: (1) characterization of the effects of acute cocaine on hemodynamics and calcium transients; (2) measurement of cocaine's effect on the MRI apparent diffusion coefficient to determine if there is cellular damage and fMRI measurements of effects of forepaw stimulation in cocaine self-administering and cocaine-naive rats to determine if there are effects on cortical functioning, (3) evaluation of the effects of abstinence from cocaine on self-administering animals as a model for the physiological changes that occur during drug withdrawal, and (4) making technical improvements on the ODF system to reduce the size of the optical probe (currently 3mm) to 300¿m. This fourth aim should permit measurements of neural signals from deeper brain regions in future studies. The PI is seeking this K25 award to further extend her knowledge of the physiology, biochemistry and pharmacology underlying the brain's responses to acute and chronic administration of abused drugs.