Unrestricted weight bearing as a method for assessment of nociceptive behavior in a model of tibiofemoral osteoarthritis in rats

Copyright © 2013 Lise Skøtt Gregersen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Novel preclinical models for prediction of osteoarthritis-like pain are necessary for the elucidation of osteoarthritis (OA) pathology and for assessment of novel analgesics. A widely used behavioral test in rat models of tibiofemoral OA is hind limb weight bearing (WB). However, this method evaluates WB in an unnaturally restricted manner. The aim of this study was therefore to characterize the Tekscan Pressure Measurement System as a means to assess OA-like tibiofemoral pain in rats by determination of plantar pressure distribution in a more natural and unre-stricted position, defined as unrestricted WB. Methods: Intra-articular injections of 1 mg monosodium iodoacetate (MIA) or saline were administrated in the left hind knee of 84 male Sprague Dawley rats. Changes in unrestricted WB between ipsilateral and contralateral hindlimbs were determined. Morphine (5 mg/kg administered subcutaneously) and naproxen (60 mg/kg per-oral) were examined for their ability to reverse WB changes. Results: Changes in hind limb unrestricted WB were observed 14 (P < 0.05), 21 (P < 0.001) and 28 (P < 0.001) days post intra-articular injections of MIA compared to control. These alterations were attenuated by morphine 1 hour post administration compared to base-line but were not affected by naproxen. Conclusion: This study indicated that unrestricted WB assessed by the Teksca

Assessment of pain response in capsaicin-induced dynamic mechanical allodynia using a novel and fully automated brushing device

BACKGROUND: Dynamic mechanical allodynia is traditionally induced by manual brushing of the skin. Brushing force and speed have been shown to influence the intensity of brush-evoked pain. There are still limited data available with respect to the optimal stroke number, length, force, angle and speed. Therefore, an automated brushing device (ABD) was developed, for which brushing angle and speed could be controlled to enable quantitative assessment of dynamic mechanical allodynia