Kimmerly D S, Wong S W, Salzer D, Menon R, Shoemaker J K
Neurovascular Research Laboratory, Faculty of Health Sciences and School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.
Am J Physiol Heart Circ Physiol. 2007 Jul;293(1):H299-306. doi: 10.1152/ajpheart.00044.2007. Epub 2007 Mar 9.
The cortical regions representing peripheral autonomic reactions in humans are poorly understood. This study examined whether changes in forebrain activity were associated with the altered physiological responses to lower body negative pressure (LBNP) following a single bout of dynamic exercise (POST-EX). We hypothesized that, compared with the nonexercised condition (NO-EX), POST-EX would elicit greater reductions in stroke volume (SV) and larger increases in heart rate (HR) and muscle sympathetic nerve activity (MSNA) during LBNP (5, 15, and 35 mmHg). Forebrain neural activity (n = 11) was measured using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging. HR, SV, arterial blood pressure (ABP), and MSNA were collected separately. Compared with NO-EX, baseline ABP was reduced, whereas HR and total vascular conductance (TVC) were elevated in POST-EX (P < 0.05). In both conditions, 5 mmHg LBNP did not elicit a change (from baseline) in any physiological parameter. Compared with NO-EX, 35 mmHg LBNP-mediated decreases in SV and TVC produced greater increases in HR and MSNA during POST-EX (P < 0.05). The right posterior insula and dorsal anterior cingulate cortex demonstrated a larger decrease in BOLD at 5 mmHg LBNP but greater BOLD increase at 15 and 35 mmHg LBNP POST-EX vs. NO-EX (P < 0.005). Conversely, the thalamus and ventral medial prefrontal cortex displayed the opposite BOLD activity pattern (i.e., larger increase at 5 mmHg LBNP but greater decrease at 15 and 35 mmHg LBNP POST-EX vs. NO-EX). Our findings suggest that discrete forebrain regions may be involved with the generation of baroreflex-mediated sympathetic and cardiovascular responses elicited by moderate LBNP.
人类中代表外周自主反应的皮质区域目前了解甚少。本研究探讨了在单次动态运动（运动后）后，前脑活动的变化是否与下体负压（LBNP）引起的生理反应改变有关。我们假设，与未运动状态（未运动）相比，运动后在LBNP（5、15和35 mmHg）期间，心输出量（SV）的降低幅度会更大，心率（HR）和肌肉交感神经活动（MSNA）的增加幅度会更大。使用血氧水平依赖（BOLD）功能磁共振成像测量前脑神经活动（n = 11）。分别收集HR、SV、动脉血压（ABP）和MSNA。与未运动相比，运动后基线ABP降低，而HR和总血管电导（TVC）升高（P < 0.05）。在两种状态下，5 mmHg的LBNP均未引起任何生理参数（相对于基线）的变化。与未运动相比，35 mmHg的LBNP介导的SV和TVC降低在运动后引起HR和MSNA的更大增加（P < 0.05）。右侧后岛叶和背侧前扣带回皮质在5 mmHg的LBNP时BOLD下降幅度更大，但在运动后15和35 mmHg的LBNP时，相对于未运动，BOLD增加幅度更大（P < 0.005）。相反，丘脑和腹内侧前额叶皮质表现出相反的BOLD活动模式（即，在5 mmHg的LBNP时增加幅度更大，但在运动后15和35 mmHg的LBNP时相对于未运动下降幅度更大）。我们的研究结果表明，离散的前脑区域可能参与了由中度LBNP引起的压力反射介导的交感神经和心血管反应的产生。
