Adaptations of arterial and venous systems following muscular inactivity

当日常体位挑战减少时（如长时间卧床休息后），心血管系统对从卧位到直立位的体位变化没有充分的反应，可能发生低血压、头晕和昏厥。我们希望使用后肢减重（HLU）大鼠模型来研究与肌肉不活动相关的循环紊乱的原因。HLU包括通过尾部挽具将大鼠悬挂在头向下倾斜的位置，以减少后腿肌肉活动。老鼠可以在前肢上自由活动。我们想知道大鼠的后躯是否有过量的一氧化氮（NO）的产生，以及阻断NO的产生是否会减轻循环异常。一氧化氮是一种强大的血管扩张剂，过多的一氧化氮会导致低血压，减少流向大脑的血液，从而导致头晕和/或昏厥。我们发现，在HLU治疗2周后，相对于颈部和头部区域的血管床，大鼠后躯的血管收缩受损。我们想知道这种损伤是否与一氧化氮分泌增加或血压控制系统如交感神经系统和肾素-血管紧张素系统的损伤有关。这项研究的目的是增加我们对血管功能因不活动而改变的机制的理解。

When there is reduced daily postural challenge (as after prolonged bed rest), the cardiovascular system does not respond adequately to postural change from lying down to the upright position, and hypotension, dizziness and fainting may occur. We wish to use the hind limb unweighting (HLU) rat model to investigate the cause of circulatory derangement associated with muscular inactivity. HLU involves suspending a rat via a tail harness at a head-down tilt position to reduce hindquarter muscular activity. The rats can move around freely on the front limbs. We want to know if there is excessive production of nitric oxide (NO) in the hindquarter of the rat, and if blockade of NO production will alleviate the circulatory abnormality. NO is a strong dilator of blood vessels, and too much of it can cause low blood pressure as well as reduce blood flow to the brain thereby causing dizziness and/or fainting. We have found that following 2 weeks of HLU, vascular bed at the hindquarter of the rat, relative to those in the neck and head region, have impaired vasoconstriction. We want to find out if the impairment is related to increased production of NO or impairment of blood pressure controlling systems such as the sympathetic nervous system, and the renin-angiotensin system. This proposed study is aim to increase our understanding of the mechanism by which vascular function is altered by inactivity.