In a previous study we have used immunohistochemical methods to localize TNFR1 and TNFR2 in lumbar dorsal root ganglia (DRGs) of the adult rat. We have localized TNFR1 in about 57% and TNFR2 in about 61% of the neuronal profiles. In the present experiments we extended these studies in two ways. First, we used double-labelling techniques and assessed whether TNFR1 is colocalized with the TRPV1 receptor which is important for the development of thermal hyperalgesia. Second, we used PCR to detect mRNA of TNFa and TNFR1 in lumbar DRGs in order to verify the expression of TNFa and TNFR1 in DRGs with a second method. Lumbar DRGs (L1-L5) were removed from both sides from normal rats, weighed, shock freezed and stored at - 80°C. After totalRNA extraction, treatment with DNase and cDNA-synthesis we made PCR experiments with the thermocycler from Biometra. With double-labelling we found that 68,2 ± 6% of the DRG-neurones with TNFR1-like immunoreactivity (IR) showed also TRPV1-like IR. On the other hand 74,7 ± 6% of neurones with TRPV1-like IR showed also expression of TNFR1-like IR. These data show considerable overlap of TNFR1 and TPRV1. The PCR data show mRNA for both TNFa and TNFR1 and thus confirm the expression of these molecules in the DRGs.