Iloprost, a stable analogue of PGI2, potentiates the hyperthermic effect of PGE2 in rats. 
Centrally mediated effects of iloprost, a stable analogue of PGI2, on rectal temperature have been investigated in conscious rats.  ICV administration of iloprost (100-1,000 ng, ICV) produced a dose-dependent, monophasic hyperthermic response that was not inhibited by indomethacin.  When injected into the preoptic anterior hypothalamic (POAH) region, iloprost (2-50 ng/POAH) induced a biphasic increase in rectal temperature.  While the first phase was inhibited by AH 6809, an E1-type prostaglandin (EP1) receptor antagonist, the second phase was abolished by indomethacin pretreatment.  Iloprost was found not to alter rectal temperature when injected into the ventromedial hypothalamic area.  Administration of iloprost into the POAH in a dose that had no effect on rectal temperature significantly potentiated the hyperthermic effect of PGE2 (50 ng, ICV).  These findings suggest that the pyrogenic effect of iloprost is partly mediated by EP1 receptors located on the POAH.  Regarding the similarities of iloprost and PGI2, it is further proposed that endogenous PGI2 might act to modulate hyperthermic effect of PGE2 released during arachidonic acid- or endogenous pyrogen-induced fever.