Expression of interleukin-6 (IL-6) and interleukin-6 receptor (IL-6R) mRNAs in rat brain during postnatal development.

Using RT-PCR, the development profile of interleukin-6 (IL-6) and its receptor (IL-6R) mRNAs in rat brain was investigated. Our results indicate that IL-6 and IL-6R mRNAs are coexpressed and are developmentally regulated in a tissue-specific manner. Highest levels of both transcripts were detected in the adult hippocampus. Most pronounced developmental changes of IL-6 message levels were observed in the rat striatum increasing up to 8-fold. By contrast, in all other regions such as neocortex, hippocampus, cerebellum and pons/medulla oblongata only minor changes (2- to 3-fold) in IL-6 expression were seen. In most tissues IL-6 mRNA levels peaked at day 20. Marked induction of the receptor message levels was detected in the striatum, hippocampus and neocortex (8- to 10-fold) whereas no changes were observed in the cerebellum and the pons/medulla oblongata. The expression pattern of both genes in various brain areas during postnatal development strongly supports the concept of IL-6 as a candidate for a new neurotrophic factor.