Fever is mediated by prostaglandin E₂ (PGE₂) produced in brain endothelial cells. Among PGE₂-synthesizing enzymes, the roles and cellular localization of cyclooxygenase-2 (COX-2) and microsomal-type PGE synthase (mPGES) in fever are well established. However, the type and localization of phospholipase A₂ (PLA₂) working in the upstream of COX-2 is unknown. We here show a possible involvement of calcium-independent PLA₂ (iPLA₂) in LPS-induced fever and other inflammatory responses. Male rats pretreated with an inhibitor of iPLA₂ (BEL, 20 mg/kg, i.p.) showed significantly suppressed fever response to LPS (10 μg/kg i.v.) administered 2 h later. PGE₂ concentration in the cerebrospinal fluid sampled 2 h after LPS injection was significantly lower in BEL-treated rats than that in vehicle-treated rats. Subarachnoidal blood vessels isolated from BEL-treated rats 2 h after LPS injection and incubated ex vivo released less amount of PGE₂ than those from vehicle-treated rats. LPS-induced expression of COX-2 and mPGES in brain endothelial cells were suppressed in BEL-treated rats. Moreover, plasma levels of inflammatory cytokines such as IL-1β and TNFα were also lower in BEL-treated rats. These results suggest that iPLA₂ is involved in fever and brain PGE₂ production in response to LPS. Contrary to our initial expectation, iPLA₂ seems to play a proinflammatory role in the earlier stage of LPS-induced responses rather than just upstream of COX-2 in brain endothelial cells. [Jpn J Physiol 55 Suppl:S218 (2005)]