Cardiovascular variability and baroreceptor reflex sensitivity over a 14-day tail suspension in rats

To verify whether a long-term weightlessness simulation was associated with development of cardiovascular deconditioning, male Wistar rats were tail suspended for 13 days and then removed for a 24-h recovery. Blood pressure (BP) and heart rate (HR) responses, their spectral properties, and the pharmacologically tested baroreceptor reflex sensitivity were studied throughout the suspension period and after removal from the tail suspension device. BP, HR, and their variability were not altered over the experimental period, and there were no indications of orthostatic 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 sensitivity. These results taken together suggest that cardiovascular deconditioning may not be developed even after long-term hindlimb suspension in rats, in contrast to humans exposed to actual or simulated weightlessness. Our results raise issue with the use of tail-suspended rats as a valid model for the study of alterations in cardiovascular function induced by spaceflight in humans.