THE EFFECT OF CAFFIENE ON BRAIN IMAGING

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。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，不仅起到神经系统刺激剂的作用，还起到血管收缩的作用。最近的研究表明，腺苷拮抗剂，如咖啡因，在功能磁共振(FMRI)研究中增加了血氧水平依赖(BOLD)信号。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，还有其他多项研究表明，大脑中基线血流的变化并不能始终如一地强化大胆的信号。众所周知，长期使用咖啡因会导致腺苷受体数量增加，已有研究表明，在戒断状态下，不同剂量的咖啡因对静息脑血流和BOLD信号变化有不同的影响。咖啡因对大胆的功能磁共振成像测量的影响是相当有趣的，因为咖啡因既影响脑细胞活动，也影响大脑中的血液流动。关于神经和血管腺苷反应对BOLD信号的贡献，仍然存在着显著的知识差距。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有效的大胆信号增强剂(与饮食中的咖啡因摄入量无关)。此外，这些研究将提供对腺苷受体亚系统(神经和血管)的迫切需要的见解，这是导致观察到的发现的原因。

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.