Retrograde transport of TNF-α and TNFR1 expression in DRG. (A) After CFA injection (48 hours), TNF-α (labeled with Alexa Fluor 488) was injected into rat hindpaw with free Alexa Fluor 488 as a control. Twenty-four hours later, saphenous nerve was isolated and fluorescent signals were detected using a fluorescence microscope. Photomicrographs illustrate three different segments: Distal, middle and proximal. Scale bars, 50 μm. Inserts illustrate magnified axon fibers labeled with Alexa Fluor 488 with scale bars of 20 μm. (B-C) Photomicrographs illustrate TNFR1 immunoreactivity, detected by immunefluorescent stain. (B) Seventy-two hours after CFA injection, L3-L5 DRGs were collected. (C) TNF-α treatment for 48 hours in DRG cultures. Scale bars, 50 μm. Bar graphs represent quantitative measurements of TNFR1 fluorescent intensity. The data are presented as fluorescent intensity of immunopositive neurons, expressed as mean ± SEM and were analyzed using an un-paired Student's t-test. **p < 0.01 (N = 3 per group); compared to control.