Nerve growth factor (NGF) and its dual structurally unrelated receptors, tropomyosin-related kinase A (TrkA) or p75 neurotrophin receptor (p75(NTR)), cause the pathogenesis of discogenic pain. To investigate the sensory innervation of injured rat lumbar intervertebral disc (IVD), we examined the expression of neuropeptides such as calcitonin gene-related peptide (CGRP) at dorsal root ganglia (DRG) by inhibiting NGF or its dual receptors. Sprague-Dawley rats with multiply punctured L5-L6 IVD were used. Six experimental groups were prepared: naïve, sham control, and four agent-treated groups with punctured IVD (vehicle, anti-NGF antibody, anti-TrkA antibody, and anti-p75(NTR) antibody). Retrograde neurotracer Fluoro-Gold (FG) was applied together except for the naïve group. Their lumbar DRG were harvested and immunolabeled for CGRP. FG-labeled DRG neurons were most prevalent at L1 and L2 DRG, and the proportion of FG-labeled CGRP-immunoreactive DRG neurons in the vehicle group was significantly elevated (p < 0.05) compared with the sham group, while those of antibody-treated groups, especially in the anti-p75(NTR) group, significantly decreased compared with the vehicle group (p < 0.05). Direct intradiscal application of antibody to NGF or its receptors suppressed CGRP expression, and p75(NTR) antagonism induced the most profound suppression.
© 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.