title: The Effect of Treatment with Resiniferatoxin and Capsaicin on Dynamic Weight Bearing Measures and Evoked Pain Responses in a Chronic Inflammatory Arthritis Murine Model.
abstract: 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.
  
  
  
  Chronic inflammatory arthritis was produced by IA injection of 30 µl of Complete Freund's Adjuvant (CFA) into the left knee of C57BL6 male mice 3 weeks prior to pain behavior testing. Mice were injected with either low or high dose IA RTX (10µl of 0.001 or 0.003%), or IA CAP (10 µL of 0.01%) 7 days prior to pain behavior testing.
  
  
  
  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.
  
  
  
  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.
authors: Rheumatology Fellowship Training Program, University of Minnesota Medical School, Minneapolis, MN, USA.
authors: Joseph
authors: J
authors: Bert
authors: Minneapolis VA Health Care System, Minneapolis, MN, USA; University of Minnesota Medical School, Minneapolis, MN, USA.
authors: Maren L
authors: ML
authors: Mahowald
authors: Minneapolis VA Health Care System, Minneapolis, MN, USA.
authors: Sandra
authors: S
authors: Frizelle
authors: Minneapolis VA Health Care System, Minneapolis, MN, USA.
authors: Christopher W
authors: CW
authors: Dorman
authors: Minneapolis VA Health Care System, Minneapolis, MN, USA.
authors: Sonia C
authors: SC
authors: Funkenbusch
authors: Minneapolis VA Health Care System, Minneapolis, MN, USA; University of Minnesota Medical School, Minneapolis, MN, USA.
authors: Hollis E
authors: HE
authors: Krug
keywords: Pain; capsaicin; intra-articular; resiniferatoxin; vanilloid