THE EFFECT OF CAFFIENE ON BRAIN IMAGING

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。咖啡因是世界上使用最广泛的神经兴奋剂，存在于各种食物和饮料中。咖啡因阻断腺苷受体，不仅作为神经系统兴奋剂，而且作为血管收缩剂。最近的研究表明，腺苷拮抗剂，如咖啡因，增加血氧水平依赖（BOLD）信号在功能磁共振（fMRI）研究。有人提出，BOLD信号的这种增强是由于静息脑血流量的减少。然而，有多项其他研究表明，大脑中基线血流量的变化并不总是加强BOLD信号。众所周知，长期使用咖啡因会导致腺苷受体数量增加，并且已经表明，在戒断状态下，一定剂量的咖啡因对静息脑血流和BOLD信号变化有不同的影响。咖啡因对BOLD功能磁共振成像测量的影响是相当感兴趣的，因为咖啡因会影响脑细胞活动和大脑中的血流。关于神经和血管腺苷反应对BOLD信号的贡献，仍然存在显著的知识差距。这里提出的研究将澄清已发表的文献，并确定咖啡因是否是一种有效的BOLD信号增强剂（无论饮食中咖啡因的摄入量如何）。此外，这些研究将提供对腺苷受体子系统（神经与血管）的深入了解，这些子系统是观察到的结果的原因。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Caffeine is the most widely used neurostimulant in the world and is found in a variety of foods and beverages. Caffeine blocks adenosine receptors and acts not only as a nervous system stimulant but also as a vasoconstrictor. Recent studies have suggested that adenosine antagonists, such as caffeine, increase the blood oxygenation level dependent (BOLD) signal in functional magnetic resonance (fMRI) studies. It has been proposed that this enhancement of the BOLD signal is due to a decrease in resting brain blood flow. However, there are multiple other studies demonstrating that changes in baseline blood flow in the brain do not consistently strengthen the BOLD signal. It is well known that chronic caffeine use causes an increase in the number of adenosine receptors, and it has been shown that in a withdrawal state, a dose of caffeine has different effects on resting cerebral blood flow and BOLD signal changes. The effects of caffeine on BOLD fMRI measures are of considerable interest because caffeine affects both brain cell activity and blood flow in the brain. There remains a significant knowledge gap concerning the contribution of neural and vascular adenosine responses to the BOLD signal. The studies proposed here will clarify the published literature and determine if caffeine is an effective BOLD signal enhancer (regardless of dietary caffeine consumption). In addition, these studies will provide much needed insights into the adenosine receptor sub-system (neural vs. vascular) that are responsible for the observed findings.