Amount of trkB, BDNF and CGRP protein in DRG after intraplantar TNF-α injection. After TNF-α injections (twice daily for three days), levels of trkB, BDNF and CGRP were measured in L3-L5 DRGs. Protein expression was detected by the standard immunohistochemical ABC method. (A) Quantitative measurements of trkB, BDNF and CGRP immunoreactivity in DRG sections. Data are presented as percentage of immuno-positive neurons in L3-L5 DRGs. (B-G) Photomicrographs illustrate the immunoreactivity of trkB, BDNF and CGRP in L4 DRG sections. (B-D), control group; (E-G), TNF-α group. Scale bars, 50 μm. Control, ctr (contra): contralateral to TNF-α. TNF-α (ipsi): injected. Data are expressed as mean ± SEM and were analyzed using an un-paired Student's t-test. *p < 0.05, **p < 0.01; compared to corresponding controls (contralateral to TNF-α injection). N = 9 per group.