Ogoh Shigehiko, Brothers R Matthew, Barnes Quinton, Eubank Wendy L, Hawkins Megan N, Purkayastha Sushmita, O-Yurvati Albert, Raven Peter B
Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA.
J Physiol. 2005 Dec 1;569(Pt 2):697-704. doi: 10.1113/jphysiol.2005.095836. Epub 2005 Oct 6.
We examined the relationship between changes in cardiac output and middle cerebral artery mean blood velocity (MCA V(mean)) in seven healthy volunteer men at rest and during 50% maximal oxygen uptake steady-state submaximal cycling exercise. Reductions in were accomplished using lower body negative pressure (LBNP), while increases in were accomplished using infusions of 25% human serum albumin. Heart rate (HR), arterial blood pressure and MCA V(mean) were continuously recorded. At each stage of LBNP and albumin infusion was measured using an acetylene rebreathing technique. Arterial blood samples were analysed for partial pressure of carbon dioxide tension (P(a,CO2). During exercise HR and were increased above rest (P < 0.001), while neither MCA V(mean) nor P(a,CO2) was altered (P > 0.05). The MCA V(mean) and were linearly related at rest (P < 0.001) and during exercise (P = 0.035). The slope of the regression relationship between MCA V(mean) and at rest was greater (P = 0.035) than during exercise. In addition, the phase and gain between MCA V(mean) and mean arterial pressure in the low frequency range were not altered from rest to exercise indicating that the cerebral autoregulation was maintained. These data suggest that the associated with the changes in central blood volume influence the MCA V(mean) at rest and during exercise and its regulation is independent of cerebral autoregulation. It appears that the exercise induced sympathoexcitation and the change in the distribution of between the cerebral and the systemic circulation modifies the relationship between MCA V(mean) and .
我们研究了7名健康男性志愿者在静息状态以及50%最大摄氧量稳态次极量骑行运动期间心输出量变化与大脑中动脉平均血流速度（MCA V(mean)）之间的关系。通过下体负压（LBNP）实现心输出量降低，而通过输注25%人血清白蛋白实现心输出量增加。连续记录心率（HR）、动脉血压和MCA V(mean)。在LBNP和白蛋白输注的每个阶段，使用乙炔再呼吸技术测量心输出量。分析动脉血样本中的二氧化碳分压（P(a,CO2)）。运动期间，HR和心输出量高于静息水平（P < 0.001），而MCA V(mean)和P(a,CO2)均未改变（P > 0.05）。静息时和运动期间，MCA V(mean)与心输出量呈线性相关（静息时P < 0.001，运动时P = 0.035）。静息时MCA V(mean)与心输出量之间回归关系的斜率大于运动时（P = 0.035）。此外，低频范围内MCA V(mean)与平均动脉压之间的相位和增益从静息到运动未改变，表明脑自动调节得以维持。这些数据表明，与中心血容量变化相关的心输出量在静息和运动时影响MCA V(mean)，其调节独立于脑自动调节。似乎运动诱发的交感神经兴奋以及脑循环和体循环之间心输出量分布的变化改变了MCA V(mean)与心输出量之间的关系。
