Zhang Y, Weaver L, Ibeawuchi A, Olson K R
Indiana University School of Medicine, South Bend Center for Medical Education, University of Notre Dame 46556, USA.
Am J Physiol. 1998 Apr;274(4):R1195-202. doi: 10.1152/ajpregu.1998.274.4.R1195.
The significance of the sympathetic nervous system (SNS) in regulating peripheral vascular resistance and cardiac function in fish has been well established, whereas its effect on venous function in vivo is unknown. Two protocols were employed in the present study to evaluate SNS effects on the venous system in intact, unanesthetized trout. In the first, trout were instrumented with pressure cannulas in the ventral (PVA) and dorsal (PDA) aortas and ductus Cuvier (PVEN), and cardiac output (CO) was measured with a flow probe around the ventral aorta. Heart rate, stroke volume, and gill and systemic resistances were calculated from the measured parameters. In the second group, vascular capacitance curves were obtained by monitoring mean circulatory filling pressure (PVEN) during transient interruption of CO and while blood volume was adjusted between 80 and 120% of normal. Unstressed blood volume (USBV) and vascular compliance (C) were derived from the capacitance curves. Infusion of epinephrine (Epi; 3.3 nmol.min-1.kg body wt-1) increased PVA, PDA, and PVEN, whereas norepinephrine (NE) infusion (3.3 nmol.min-1.kg body wt-1) increased PVA and PDA but did not affect PVEN. Epi (1.0 nmol.min-1.kg body wt-1), but not NE (2.6 or 10.4 nmol.min-1.kg body wt-1), displaced the capacitance curve to the right and significantly decreased USBV. Inhibition of alpha 1-adrenoceptors with prazosin, or ganglionic nicotinic receptor blockade with hexamethonium, produced a left shift in the capacitance curve, and both treatments increased USBV and C. Conversely, the alpha-adrenoceptor antagonist phentolamine did not effect vascular capacitance. These results show that Epi has potent effects on trout veins in vivo and that it mobilizes blood from the unstressed into the stressed vascular compartment and augments central venous pressure by decreasing venous compliance. These results also show that the SNS is an active effector of venous tone and compliance in trout; this is the first demonstration of tonic regulation of vascular capacitance in any fish.
交感神经系统（SNS）在调节鱼类外周血管阻力和心脏功能方面的重要性已得到充分证实，但其对体内静脉功能的影响尚不清楚。本研究采用两种方案来评估SNS对完整、未麻醉的虹鳟鱼静脉系统的影响。第一种方案中，在虹鳟鱼的腹主动脉（PVA）、背主动脉（PDA）和居维叶氏管（PVEN）中插入压力套管，并使用围绕腹主动脉的流量探头测量心输出量（CO）。根据测量参数计算心率、每搏输出量以及鳃和全身阻力。在第二组实验中，通过在CO短暂中断期间以及将血容量调整至正常的80%至120%时监测平均循环充盈压（PVEN）来获得血管容量曲线。无应激血容量（USBV）和血管顺应性（C）由容量曲线得出。肾上腺素（Epi；3.3 nmol·min⁻¹·kg体重⁻¹）输注增加了PVA、PDA和PVEN，而去甲肾上腺素（NE）输注（3.3 nmol·min⁻¹·kg体重⁻¹）增加了PVA和PDA，但未影响PVEN。Epi（1.0 nmol·min⁻¹·kg体重⁻¹）而非NE（2.6或10.4 nmol·min⁻¹·kg体重⁻¹）使容量曲线右移并显著降低了USBV。用哌唑嗪抑制α1 - 肾上腺素能受体或用六甲铵阻断神经节烟碱受体，使容量曲线左移，且两种处理均增加了USBV和C。相反，α - 肾上腺素能受体拮抗剂酚妥拉明对血管容量无影响。这些结果表明，Epi对虹鳟鱼体内静脉有显著作用，它将血液从未应激血管腔动员到应激血管腔，并通过降低静脉顺应性增加中心静脉压。这些结果还表明，SNS是虹鳟鱼静脉张力和顺应性的主动调节因子；这是首次在任何鱼类中证明对血管容量的紧张性调节。
