Effect of 3-week suspension on sympathetic vasoconstrictor response in rat.

One of the main problems arising after gravitational unloading is an orthostatic intolerance leading to failure in supporting the upright posture and performing natural locomotion. Among a number of causes for the orthostatic intolerance the decreased circulating blood volume, increased venous distention, alterations in microcirculation, loss of muscular tonus, and regulatory disturbances could be mentioned. The later cause has been intensively studied recently. The aim of the present study is to examine the alterations induced by simulated gravitational unloading in the reaction of resistance vessels of isolated hind limb to the sympathetic stimuli in rats.