Conclusion
Using ADWB and EPS, we quantified pain in a murine chronic inflammatory arthritis model. IA CFA caused a significant increase in EPS and decreased ADWB measures in the affected limb. Treatment with IA RTX and CAP produced significant improvement in EPS in mice with mono-articular inflammatory arthritis. IA vanilloid treatment produced no improvement in ADWB measurements for weight and for time.
Objective
Capsaicin (CAP) and Resiniferatoxin (RTX) are vanilloid receptor agonists that can normalize Evoked Pain Scores (EPS) and Automated Dynamic Weight Bearing (ADWB) measures in murine acute inflammatory arthritis when given by intra-articular (IA) injection. To determine whether these vanilloid receptor agonists have benefit in Complete Freund's Adjuvant (CFA) induced chronic inflammatory arthritis pain, we measured changes in ADWB and EPS in arthritic mice with and without treatment with IA CAP and RTX.
Results
Chronic Inflammatory arthritis pain produced increased EPS and reduced ADWB measures for weight bearing in the affected limb of arthritic mice compared to naïve mice. ADWB measurements for time in CFA when compared with Naive were not significantly different, but suggested off-loading the arthritic limb to the normal limb. Treatment with IA CAP or RTX 7 days prior to pain behavior testing produced significant improvement in EPS but no improvement in ADWB measures. Neither IA CAP nor IA RTX had any impact on EPS or ADWB measurements in non-arthritic mice when given 7 days prior to pain behavioral testing.