CARDIOVASCULAR VARIABILITY AND BARORECEPTOR REFLEX SENSITIVITY OVER A14-DAY TAIL SUSPENSION IN RATS

To verify whether a long-term weightlessness simulation was associated with development of cardiovascular deconditioning, male Wistar rats w ere tail suspended for 13 days and then removed for a 24-h recovery. B lood pressure (BP) and heart rate (HR) responses, their spectral prope rties, and the pharmacologically tested baroreceptor reflex sensitivit y were studied throughout the suspension period and after removal from the tail suspension device. BP, HR, and their variability were not al tered over the experimental period, and there were no indications of o rthostatic intolerance on release from head-down suspension. Spectral properties of BP and HR were unchanged during the experiment, and tail suspension did not induce modifications in the baroreceptor reflex se nsitivity. These results taken together suggest that cardiovascular de conditioning may not be developed even after long-term hindlimb suspen sion in rats, in contrast to humans exposed to actual or simulated wei ghtlessness. Our results raise issue with the use of tail-suspended ra ts as a valid model for the study of alterations in cardiovascular fun ction induced by spaceflight in humans.