Effect of conditions of three-dimensional clinostating on carrageenin-induced paw oedema and hyperalgesia in rat

During space flight the constant influence of weightlessness leads to several modifications of many physiological processes. This study aimed to determine whether conditions of mod-elled microgravity, using a three-dimensional clinostat (Random Positioning Machine, RPM), influence the effect of carrageenin-induced paw oedema and thermal hyperalgesia, common models of acute inflammation and hyperalgesia in rat. The experimental data indicate that RPM significantly reduced the carrageenin-induced oedema associated to a more pronounced decrease in body weight with respect to control groups. RPM-induced anti-inflammatory ef-fect was not modified by pre-treatment with mifepristone, a glucocorticoid receptor antago-nist, ruling out a possible influence of a stress-related increase of cortisol release during the RPM-treatment. Moreover, acetilsalicilic acid treatment on RPM-exposed rats did not produce any effect after carrageenin-challenge. Furthermore, in agreement with the first experiment, a significant inhibition of the carrageenin-evoked thermal hyperalgesia in rats exposed to RPM was observed. The mechanism by which the anti-inflammatory and anti-hyperalgesic effect induced by RPM occurs remains to be determined, although, we cannot rule out the possibility of an effect on cyclooxygenase or some other enzyme of the arachidonic acid cascade.