Twenty four hours head-down tilt decreases arterial baroreflex function in conscious rat.

In human zero gravity induces a cardiovascular deconditioning. The transfer of blood from the periphery to the thoracic compartment, occuring immediately at the beginning of the exposure to microgravity seems to be involved in this phenomenon. We have previously shown that LBNP (-40 mm Hg) produced an exaggerated heart rate response at the end of 24 hours of bed rest without modification of the cardiopulmonary receptors in human. Some other studies have shown that microgravity induces an impairment of the baroreflex sensitivity in human, but its involvement in the cardiovascular deconditioning is not completely understood. The aim of this study was to determine the modification of the arterial baroreflex using a model of simulated weightlessness in conscious rats during the exposure to microgravity.