Patients with RA showed production of peripheral pain agents, pro-inflammatory cytokines (IL-1, IL-6 and TNF with different actions on responsiveness of Aδ-fibers, C-fibers and the effect of neutralization on mechanical hyperalgesia) and nerve growth factor in synovium or synovial fluid, which sensitized peripheral receptors [70]. The gene discussed is TNF; the disease is rheumatoid arthritis.