Skovgaard Nini, Conlon J Michael, Wang Tobias
Zoophysiology, Department of Biological Sciences, Aarhus University, 8000 Aarhus C, Denmark.
Am J Physiol Regul Integr Comp Physiol. 2007 Sep;293(3):R1393-9. doi: 10.1152/ajpregu.00256.2007. Epub 2007 Jun 13.
Digestion of large meals in pythons produces substantial increases in heart rate and cardiac output, as well as a dilation of the mesenteric vascular bed leading to intestinal hyperemia, but the mediators of these effects are unknown. Bolus intra-arterial injections of python neurotensin ([His(3), Val(4), Ala(7)]NT) (1 - 1,000 pmol/kg) into the anesthetized ball python Python regius (n = 7) produced a dose-dependent vasodilation that was associated with a decrease in systemic pressure (P(sys)) and increase in systemic blood flow (Q(sys)). There was no effect on pulmonary pressure and conductance. A significant (P < 0.05) increase in heart rate (f(H)) and total cardiac output (Q(tot)) was seen only at high doses (>30 pmol/kg). The systemic vasodilation and increase in Q(tot) persisted after beta-adrenergic blockade with propranolol, but the rise in f(H) was abolished. Also, the systemic vasodilation persisted after histamine H(2)-receptor blockade. In unanesthetized pythons (n = 4), bolus injection of python NT in a dose as low as 1 pmol/kg produced a significant increase in blood flow to the mesenteric artery (177% +/- 54%; mean +/- SE) and mesenteric conductance (219% +/- 74%) without any increase in Q(sys), systemic conductance, P(sys), and f(H). The data provide evidence that NT is an important hormonal mediator of postprandial intestinal hyperemia in the python, but its involvement in mediating the cardiac responses to digestion may be relatively minor.
蟒蛇消化大餐时，心率和心输出量会大幅增加，同时肠系膜血管床扩张导致肠道充血，但这些效应的介质尚不清楚。将蟒蛇神经降压素（[His(3), Val(4), Ala(7)]NT）（1 - 1000 pmol/kg）经动脉大剂量注射到麻醉的球蟒（Python regius）（n = 7）体内，会产生剂量依赖性血管舒张，这与体循环压力（P(sys)）降低和体循环血流量（Q(sys)）增加有关。对肺循环压力和肺导纳没有影响。仅在高剂量（>30 pmol/kg）时，心率（f(H)）和总心输出量（Q(tot)）才会显著（P < 0.05）增加。用普萘洛尔进行β-肾上腺素能阻断后，体循环血管舒张和Q(tot)增加仍持续存在，但f(H)的升高被消除。此外，组胺H(2)受体阻断后，体循环血管舒张仍持续存在。在未麻醉的蟒蛇（n = 4）中，低至1 pmol/kg剂量的蟒蛇神经降压素大剂量注射会使肠系膜动脉血流量（177% +/- 54%；平均值 +/- 标准误）和肠系膜导纳（219% +/- 74%）显著增加，而Q(sys)、体循环导纳、P(sys)和f(H)均无增加。这些数据表明，神经降压素是蟒蛇餐后肠道充血的重要激素介质，但其在介导消化引起的心脏反应中的作用可能相对较小。
