Continuous measurement of hindquarter resistance changes to nerve stimulation and intraarterial drug administration in rats.

Changes in vascular reactivity are thought to play an important role in the maintenance and/or pathogenesis of various disorders of the cardiovascular system including hypertension. In some animal models, results of studies examining reactivity of the hindquarters vasculature using different techniques are conflicting. The purpose of this study was to validate a new method for measuring vascular reactivity of the hindquarters: a method based on a modification of a technique used previously for renal autoperfusion. We tested the method in spontaneously hypertensive rats (SHR) in order to allow comparison of our results to those obtained previously using other techniques. We found that reactivity of the SHR hindquarters to norepinephrine was normal (compared to that of normotensive Wistar-Kyoto control rats, WKY), while reactivity to nerve stimulation was increased (when results were expressed as an absolute change in resistance). Dilator reactivity to acetylcholine and sympathetic nerve crush was greater in SHR. Resistance of the hindquarters at maximal dilation was 25% higher in SHR. Except for the resistance at maximal dilation, these results contrast with those obtained in earlier studies using an artificial pump to perfuse SHR hindquarters with blood or artificial media. However, the results agree with those reported in conscious, adult SHR. We conclude that: 1) our autoperfusion technique allows comparatively simple vascular reactivity testing to be performed in blood-perfused hindquarters of the rat, and 2) reactivity of the SHR hindquarters to dilator stimuli may be greater than in WKY rats.