Brain-derived neurotrophic factor and vanilloid receptor subtype 1 immunoreactive sensory DRG neurons innervating the lumbar facet joints in rats

The rat L5/6 facet joint is innervated from L1 to L6 by the dorsal root ganglia (DRG). The presence of substance P- and calcitonin gene-related peptide-immunoreactive (ir) DRG neurons innervating the L5/6 facet joint has been demonstrated. However, the presence of brain-derived neurotrophic factor (BDNF)-ir and the vanilloid receptor subtype 1 (VR1)-ir DRG neurons, which relate to inflammatory and burning pain innervating the L5/6 facet joint, has not. Fluoro-gold (FG)-labeled neurons innervating the L5/6 facet joint were distributed throughout the DRGs from T13 to L6 levels. Of the FG-labeled neurons, the proportions of BDNF-ir in L1, L2, L3, L4 and L5 DRG neurons were 9%, 15%, 21%, 17% and 20% and the proportions of VR1-ir L1, L2, L3, L4 and L5 DRG neurons were 8%, 9%, 15%, 16% and 15%, respectively.