Thornton Sheila J, Hochachka Peter W, Crocker Daniel E, Costa Daniel P, Leboeuf Burney J, Spielman Daniel M, Pelc Norbert J
Department of Zoology, University of British Columbia, Vancouver, Canada.
J Exp Biol. 2005 Oct;208(Pt 19):3637-43. doi: 10.1242/jeb.01789.
The aim of this study was to examine the effect of forced diving on cardiac dynamics in a diving mammal by evaluating cardiac output and heart rate. We used MR Imaging and phase contrast flow analysis to obtain accurate flow measurements from the base of the aorta. Heart rate (fh) and cardiac output (Q) were measured before, during and after dives in four restrained juvenile northern elephant seals, Mirounga angustirostris, and stroke volume (Vs) was calculated (Vs=Q/fh). Mean Q during diving (4011+/-387 ml min(-1)) and resting (6530+/-1018 ml min(-1)) was not significantly different (paired t-test; P<0.055). Diving was accompanied by a 20% increase in Vs over the pre-dive level. Pre-dive, post-dive or diving fh was not significantly correlated with Vs during any state. Diving Vs correlated negatively with the bradycardic ratio (diving fh to pre-dive fh). In this study, the degree of bradycardia during diving was less than in previous pinniped studies, suggesting that the reduction in vagal input may contribute to the observed increase in Vs.
本研究的目的是通过评估心输出量和心率，来研究强制潜水对一种潜水哺乳动物心脏动力学的影响。我们使用磁共振成像和相位对比血流分析，从主动脉根部获取准确的血流测量值。在4只被束缚的幼年北象海豹（Mirounga angustirostris）潜水前、潜水期间和潜水后测量心率（fh）和心输出量（Q），并计算每搏输出量（Vs）（Vs = Q/fh）。潜水期间的平均Q（4011±387 ml·min⁻¹）和静息时的平均Q（6530±1018 ml·min⁻¹）无显著差异（配对t检验；P<0.055）。潜水时Vs比潜水前水平增加了20%。在任何状态下，潜水前、潜水后或潜水时的fh与Vs均无显著相关性。潜水时的Vs与心动过缓比率（潜水时的fh与潜水前的fh之比）呈负相关。在本研究中，潜水时的心动过缓程度低于先前对鳍足类动物的研究，这表明迷走神经输入的减少可能导致了观察到的Vs增加。
