Dept. of Physiology, Midwestern Univ., 555-31st St., Downers Grove, IL 60515, USA.
Am J Physiol Regul Integr Comp Physiol. 2010 Jan;298(1):R224-34. doi: 10.1152/ajpregu.00592.2009. Epub 2009 Nov 18.
The mammalian diving response, consisting of apnea, bradycardia, and increased total peripheral resistance, can be modified by conscious awareness, fear, and anticipation. We wondered whether swim and dive training in rats would 1) affect the magnitude of the cardiovascular responses during voluntary and forced diving, and 2) whether this training would reduce or eliminate any stress due to diving. Results indicate Sprague-Dawley rats have a substantial diving response. Immediately upon submersion, heart rate (HR) decreased by 78%, from 453 +/- 12 to 101 +/- 8 beats per minute (bpm), and mean arterial pressure (MAP) decreased 25%, from 143 +/- 1 to 107 +/- 5 mmHg. Approximately 4.5 s after submergence, MAP had increased to a maximum 174 +/- 3 mmHg. Blood corticosterone levels indicate trained rats find diving no more stressful than being held by a human, while untrained rats find swimming and diving very stressful. Forced diving is stressful to both trained and untrained rats. The magnitude of bradycardia was similar during both voluntary and forced diving, while the increase in MAP was greater during forced diving. The diving response of laboratory rats, therefore, appears to be dissimilar from that of other animals, as most birds and mammals show intensification of diving bradycardia during forced diving compared with voluntary diving. Rats may exhibit an accentuated antagonism between the parasympathetic and sympathetic branches of the autonomic nervous system, such that in the autonomic control of HR, parasympathetic activity overpowers sympathetic activity. Additionally, laboratory rats may lack the ability to modify the degree of parasympathetic outflow to the heart during an intense cardiorespiratory response (i.e., the diving response).
哺乳动物潜水反应包括呼吸暂停、心动过缓和总外周阻力增加，可以通过意识、恐惧和预期来改变。我们想知道，在大鼠中进行游泳和潜水训练是否会 1）影响自愿和强制潜水期间心血管反应的幅度，以及 2）这种训练是否会减少或消除潜水引起的任何应激。结果表明，Sprague-Dawley 大鼠有明显的潜水反应。一浸入水中，心率（HR）就下降了 78%，从 453±12 次/分钟降至 101±8 次/分钟，平均动脉压（MAP）下降了 25%，从 143±1 毫米汞柱降至 107±5 毫米汞柱。大约在浸入水中 4.5 秒后，MAP 增加到最大值 174±3 毫米汞柱。血液皮质酮水平表明，训练过的大鼠发现潜水并不比被人抓住更有压力，而未训练的大鼠发现游泳和潜水非常有压力。强制潜水对训练有素和未经训练的大鼠都有压力。在自愿和强制潜水期间，心动过缓的幅度相似，而在强制潜水期间，MAP 的增加幅度更大。因此，实验室大鼠的潜水反应似乎与其他动物不同，因为大多数鸟类和哺乳动物在强制潜水期间表现出比自愿潜水更强烈的潜水性心动过缓。大鼠可能表现出自主神经系统的副交感和交感分支之间的明显拮抗作用，以至于在 HR 的自主神经控制中，副交感神经活动压倒了交感神经活动。此外，实验室大鼠可能缺乏在强烈的心肺反应（即潜水反应）期间调节心脏副交感神经输出程度的能力。
