Use of dynamic weight bearing as a novel end-point for the assessment of Freund's Complete Adjuvant induced hypersensitivity in mice.

Animal models are an integral part of pain research. However, current models tend to rely on evoked responses and there is a belief that non-evoked responses may be a more relevant behavioural readout as the animal responds in a more natural manner. Here, dynamic weight bearing (DWB), a novel method for assessing mechanical hypersensitivity, was evaluated using the Freund's Complete Adjuvant (FCA) model of inflammatory pain in mice. DWB enables the measurement of weight placed through all four paws of a freely moving animal. The data obtained from DWB was compared with data acquired using the standard static weight bearing (incapacitance) test. In both tests reversal of FCA induced mechanical hypersensitivity was investigated using the selective COX2 inhibitor celecoxib. Mice treated with FCA placed less weight through the ipsilateral hindpaw compared to vehicle controls. This reduction was reversed by celecoxib (30mg/kg p.o.) in the dynamic and static weight bearing tests. The data presented here suggests that dynamic weight bearing may provide a novel end point for the development of new analgesics.