Seebacher Frank, Franklin Craig E
Integrative Physiology, School of Biological Sciences A08, The University of Sydney, 2006 Sydney, NSW, Australia.
J Comp Physiol B. 2004 Oct;174(7):577-85. doi: 10.1007/s00360-004-0446-0. Epub 2004 Aug 31.
Reptiles change heart rate and blood flow patterns in response to heating and cooling, thereby decreasing the behavioural cost of thermoregulation. We tested the hypothesis that locally produced vasoactive substances, nitric oxide and prostaglandins, mediate the cardiovascular response of reptiles to heat. Heart rate and blood pressure were measured in eight crocodiles (Crocodylus porosus) during heating and cooling and while sequentially inhibiting nitric-oxide synthase and cyclooxygenase enzymes. Heart rate and blood pressure were significantly higher during heating than during cooling in all treatments. Power spectral density of heart rate and blood pressure increased significantly during heating and cooling compared to the preceding period of thermal equilibrium. Spectral density of heart rate in the high frequency band (0.19-0.70 Hz) was significantly greater during cooling in the saline treatment compared to when nitric-oxide synthase and cyclooxygenase enzymes were inhibited. Cross spectral analysis showed that changes in blood pressure preceded heart rate changes at low frequencies (< 0.1 Hz) only. We conclude that the autonomic nervous system controls heart rate independently from blood pressure at higher frequencies while blood pressure changes determine heart rate at lower frequencies. Nitric oxide and prostaglandins do not control the characteristic heart rate hysteresis response to heat in C. porosus, although nitric oxide was important in buffering blood pressure against changes in heart rate during cooling, and inhibition caused a compensatory decrease in parasympathetic stimulation of the heart.
爬行动物会根据受热和受冷情况改变心率和血流模式，从而降低体温调节的行为成本。我们检验了这样一个假设，即局部产生的血管活性物质一氧化氮和前列腺素介导爬行动物对热的心血管反应。在八只湾鳄（Crocodylus porosus）受热、受冷以及依次抑制一氧化氮合酶和环氧化酶时测量其心率和血压。在所有处理中，受热时的心率和血压均显著高于受冷时。与之前的热平衡期相比，受热和受冷期间心率和血压的功率谱密度显著增加。在生理盐水处理中，与抑制一氧化氮合酶和环氧化酶时相比，受冷期间高频带（0.19 - 0.70赫兹）的心率谱密度显著更大。互谱分析表明，仅在低频（< 0.1赫兹）时血压变化先于心率变化。我们得出结论，在较高频率时自主神经系统独立于血压控制心率，而在较低频率时血压变化决定心率。一氧化氮和前列腺素并不控制湾鳄对热的特征性心率滞后反应，尽管一氧化氮在缓冲受冷期间血压随心率变化方面很重要，且抑制会导致心脏副交感神经刺激的代偿性降低。
