INSULIN REDU BOLD RESP BUT IS W/O EFFECT ON THE VEP OF A VISUAL TASK IN HUMAN

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 基于血氧水平依赖(BOLD)对比的功能磁共振成像(FMRI)已成为评估活体神经元激活的宝贵工具。大胆反应的量化取决于对大脑刺激的反应所发生的血流动力学和代谢变化。然而，这些变化可能会随着胰岛素的变化而变化，胰岛素是一种已知在某些组织中具有血管活性的激素。为了确定胰岛素是否对功能磁共振成像有影响，我们测量了五名正常志愿者对视觉刺激的大胆反应，在这些志愿者中，胰岛素首先被抑制，然后被调到高生理浓度。此外，我们还通过视觉诱发电位(VEP)检测了胰岛素对视觉皮质激活的影响。我们发现，在有胰岛素存在的情况下测得的BOLD反应(血清胰岛素=236/-29pmol/L)显著低于在无胰岛素存在时测得的BOLD反应(P&lt；0.001)。在28名受试者中，胰岛素对在有或没有胰岛素的情况下获得的P100幅度或潜伏期没有影响，这些受试者使用的刺激与功能磁共振实验中使用的刺激相同。我们的观察表明，胰岛素可能对脑血流和/或代谢产生影响，从而影响BOLD信号，而这种影响不依赖于它对事件相关电位(ERP)确定的神经元激活的影响。这些发现强调了在解释胰岛素浓度和/或胰岛素敏感性不同的受试组之间功能磁共振反应的差异时必须考虑的复杂性。

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. Functional magnetic resonance imaging (fMRI) based on blood oxygen level-dependent (BOLD) contrast has become an invaluable tool in the assessment of in vivo neuronal activation. Quantification of the BOLD response is determined by the hemodynamic and metabolic changes that occur in response to brain stimulation. However, these changes may vary by changes in insulin, a hormone known to be vasoactive in some tissues. To determine if insulin has an effect on fMRI, we measured the BOLD response to a visual stimulus in five normal volunteers in which insulin was first suppressed and then brought to a high physiological concentration. In addition, we also examined the effect of insulin on activation of the visual cortex as measured by the visual-evoked potential (VEP). We found that the BOLD response measured in the presence of insulin (serum insulin=236+/-29 pmol/L) was significantly lower (P<0.001) than that measured in its absence (serum insulin=8+/-2 pmol/L). Insulin was without effect on P100 amplitude or latency acquired in the presence or absence of insulin in 28 subjects using the same stimulus as that used for the fMRI experiments. Our observations suggest that insulin may have effects on cerebral blood flow and/or metabolism that affect the BOLD signal that are independent of its effects on neuronal activation identified by event related potentials (ERP). These findings highlight the complexity that must be considered when interpreting differences in fMRI responses between groups of subjects that differ in insulin concentration and/or insulin sensitivity