Skals Marianne, Skovgaard Nini, Abe Augusto S, Wang Tobias
Department of Zoophysiology, Institute of Biological Science, Aarhus University, Denmark.
J Exp Biol. 2005 Oct;208(Pt 19):3747-59. doi: 10.1242/jeb.01828.
The effects of adrenergic stimulation on mean circulatory filling pressure (MCFP), central venous pressure (P(CV)) and stroke volume (Vs), as well as the effects of altered MCFP through changes of blood volume were investigated in rattlesnakes (Crotalus durissus). MCFP is an estimate of the upstream pressure driving blood towards the heart and is determined by blood volume and the activity of the smooth muscle cells in the veins (venous tone). MCFP can be determined as the plateau in P(CV) during a total occlusion of blood flow from the heart. Vs decreased significantly when MCFP was lowered by reducing blood volume in anaesthetised snakes, whereas increased MCFP through infusion of blood (up to 3 ml kg(-1)) only led to a small rise in Vs. Thus, it seems that end-diastolic volume is not affected by an elevated MCFP in rattlesnakes. To investigate adrenergic regulation on venous tone, adrenaline as well as phenylephrine and isoproterenol (alpha- and beta-adrenergic agonists, respectively) were infused as bolus injections (2 and 10 microg kg(-1)). Adrenaline and phenylephrine caused large increases in MCFP and P(CV), whereas isoproterenol decreased both parameters. This was also the case in fully recovered snakes. Therefore, adrenaline affects venous tone through both alpha- and beta-adrenergic receptors, but the alpha-adrenergic receptor dominates at the dosages used in the present study. Injection of the nitric oxide donor SNP caused a significant decrease in P(CV) and MCFP. Thus, nitric oxide seems to affect venous tone.
研究了肾上腺素能刺激对响尾蛇（Crotalus durissus）平均循环充盈压（MCFP）、中心静脉压（P(CV)）和每搏输出量（Vs）的影响，以及通过改变血容量对MCFP的影响。MCFP是驱动血液流向心脏的上游压力的一个估计值，由血容量和静脉平滑肌细胞的活性（静脉张力）决定。MCFP可在心脏血流完全阻断期间确定为P(CV)的平台期。在麻醉的蛇中，通过减少血容量降低MCFP时，Vs显著降低，而通过输注血液（高达3 ml kg(-1)）增加MCFP仅导致Vs小幅升高。因此，在响尾蛇中，舒张末期容积似乎不受升高的MCFP影响。为了研究肾上腺素能对静脉张力的调节，以推注方式（2和10 μg kg(-1)）分别注射肾上腺素以及去氧肾上腺素和异丙肾上腺素（分别为α和β肾上腺素能激动剂）。肾上腺素和去氧肾上腺素导致MCFP和P(CV)大幅升高，而异丙肾上腺素降低了这两个参数。在完全恢复的蛇中也是如此。因此，肾上腺素通过α和β肾上腺素能受体影响静脉张力，但在本研究使用的剂量下，α肾上腺素能受体起主导作用。注射一氧化氮供体硝普钠导致P(CV)和MCFP显著降低。因此，一氧化氮似乎影响静脉张力。
