Interleukin-1 beta stimulates corticotropin-releasing factor (CRF) secretion from the hypothalamus involving the activation of prostaglandins. This study investigated the possibility that nitric oxide (NO) acts as a mediator of interleukin-1-induced CRF release. An in vitro rat hypothalami continuous perifusion system was used. Pre- and co-incubation of hypothalami with either the NO synthase inhibitor, NG-nitro-L-arginine (1 mM), or the NO scavenger, hemoglobin (10 microM), induced a marked reduction in the effect of interleukin-1 (3 pM) on CRF secretion. The effect of NG-nitro-L-arginine was prevented by pre-exposure of hypothalami to L-arginine (1 mM). We also studied whether the involvement of NO in this interleukin-1 effect could involve a prostaglandin action. The concurrent treatment with NG-nitro-L-arginine and indomethacin (14 microM)--an inhibitor of prostaglandin production--reduced interleukin-1-induced CRF release to the same level as NG-nitro-L-arginine alone, suggesting that prostaglandins might interact with NO on this interleukin-1 effect. These results suggest that NO plays a role in the in vitro stimulatory action of interleukin-1 on hypothalamic CRF secretion.