Abstract The purpose of this study was to investigate the role of pyrogenic cytokines, such as IL-1β, IL-6 and MIP-1β, in the mechanisms underlying the hyperthermic response of rats to central injection of PGE 2. Thus, specific murine neutralizing antibodies against these cytokines were microinjected directly into the anterior hypothalamic, preoptic area (AH/POA) of unrestrained rats just before intracerebroventricular injection of PGE 2. The significant hyperthermia induced by PGE 2 was markedly suppressed by micro-injection of anti-IL-6 and partially attenuated by anti-IL-1β. However, the micro-injection of anti-MIP-1β failed to alter the hyperthermic response. The results indicate that PGE 2-induced hyperthermia is presumably mediated through actions of IL-6 on the thermosensitive cells of the AH/POA and confirm that distinct and alternate pathways exist in the rat brain for the induction of fever.