Immobilization stress increases mRNA levels of interleukin-1 receptor antagonist in various rat brain regions.

1. Interleukin-1 receptor antagonist (IL-1Ra), as well as the interleukin-1 beta (IL-1 beta) gene response to immobilization stress (IMS), was examined in the rat brain. The reverse transcription-polymerase chain reaction was employed to determine mRNA levels. 3. IL-1 beta and IL-1Ra mRNA levels peaked at approximately 0.5 and 2-4 hr, respectively. The maximum mRNA levels of IL-1 beta were 15-fold higher than pre-IMS levels, whereas those of IL-1Ra were 250-fold higher in the hypothalamus. 3. After the biosynthesis of IL-1 beta has peaked, IL-1Ra may contribute to attenuation of the IL-1 activity which has been enhanced by IMS.