A large body of evidence has implicated prostaglandin E(2) (PGE(2)) in fever production. However, the role of PGD(2) in this context is only poorly understood. We therefore determined by LC-MS/MS analyses the content of PGD(2) and PGE(2) in cerebrospinal fluid (CSF), plasma and lungs of rats over 5 hours after fever induction by intraperitoneal injection of lipopolysaccharide (LPS, 50 microg/kg). Both PGD(2) and PGE(2) were detected in CSF, plasma and lungs of saline-treated control animals. The injection of LPS evoked fever and an increase of PGE(2) in the CSF, while the CSF content of PGD(2) was not significantly altered. However, both PGE(2) and PGD(2) levels were elevated in plasma and lungs after LPS injection. Interestingly, pretreatment with a novel selective inhibitor of hematopoietic prostaglandin D synthase (H-PGDS), EDJ300520 (10-40 mg/kg p.o.), selectively and dose-dependently prevented the LPS-induced increase of PGD(2) in plasma and lungs but did not affect the PGE(2) content. Most remarkably, EDJ300520 pretreatment led to an hypothermic response after LPS injection during the first 3 h and prevented fever induction. These data indicate that PGD(2) produced peripherally by H-PGDS essentially contributes to LPS-induced fever.