FEBRILE RESPONSES INDUCED IN ADRENALECTOMIZED RATS BY ADMINISTRATION OF INTERLEUKIN-1-BETA OR PROSTAGLANDIN E(2)

1. The present study was carried out to investigate the effect of bila teral adrenalectomy on fevers induced in rats by systemic injection of interleukin-1 beta (IL-1 beta) or by central injection of prostagland in E(2) (PGE(2)). 2. Intraperitoneal (I.P.) injections of two doses of IL-1 beta (0.5 and 1.0 pg kg(-1)) induced biphasic fevers in normal c ontrol rats in a dose-dependent manner. Adrenalectomized (ADX) rats sh owed higher fevers than sham-ADX rats after I.P. injection of small do ses of IL-1 beta (0.5 mu g kg(-1)). This fever enhancement was inhibit ed by acute or chronic glucocorticoid, dexamethasone (DEX), treatment. In contrast, there was no significant difference between fevers induc ed in ADX and sham-ADX rats by I.P. injection of large doses of IL-1 b eta (1.0 g kg(-1)). 3. Dose-dependent fevers were observed in normal c ontrol rats after injections of several doses of PGE(2) (5, 25 and 100 ng) into the preoptic hypothalamic area (POA). The injection of a lar ge dose of PGE(2) (100 ng) into the POA led to a lower fever in ADX ra ts, compared with that in sham-ADX rats. This fever in ADX rats was in creased by acute or chronic treatment with DEX. On the other hand, adr enalectomy had no effect on fevers induced by the injections of small doses of PGE(2) (5 and 25 ng) 4. The injections of PGE(2) (100 ng) int o the POA induced increases in oxygen consumptions in ADX rats that we re significantly smaller than those in sham-ADX rats, suggesting that the lower PGE(2) fever was, at least in part, due to attenuated thermo genesis in ADX rats. 5. There was no significant difference in plasma osmolality between the ADX and the sham-ADX rats. The ADX rats were gi ven 0.9% salt water instead of tap water. 6. These results suggest tha t endogenous glucocorticoid is one of the important modulators of the IL-1-induced and the PGE(2)-induced fevers in rats.