RESUMO
It is well known that nerve growth factor (NGF) may serve as a link between inflammation and hyperalgesia. However, there is little information whether brain-derived neurotrophic factor (BDNF), another family of neurotrophin, may related with nociception. In the present study, in situ hybridization was used to evaluate i) the change in the level of BDNF mRNA, ii) colocalization of the trkA mRNA and BDNFmRNA and iii) colocalization of the preprotachykinin (PTT)mRNA and BDNFmRNA following peripheral inflammation produced by an intraplantar injection of Freund's adjuvant into the rat paws. The results obtained were as follows: 1. Peripheral tissue inflammation significantly increased BDNFmRNA levels in the DRG. 2. Many neurons expressing trkAmRNA showed increased expression of BDNFmRNA following peripheral inflammation. 3. Many neurons expressing PTT mRNA showed increased expression of BDNFmRNA following peripheral inflammation. 4. Intraplantar injection of antibody to NGF together with Freund's adjuvant prevent the increase in BDNFmRNA. The present results indicate that the peripheral inflammation induces an increased synthesis of BDNF which is mediated by NGF and BDNF coexist with substance P in the DRG and that BDNF may play an important role related with nociception.