Determination of inflamed paw surface temperature in rats

The surface temperature of a rat's paw is greatly affected by heat transfer because of its contacts with the body, as well as several environmental conditions. To establish a methodology for determining the surface temperature of the inflamed rat's paw, we devised an individual cage with a pair of rolling rods. The rods were set to protect contacts of paws with the body and were devised to roll easily when rats put their feet on the rods. When a rat was transferred to the individual cage with rolling rods from a group cage, the surface temperature of a normal or inflamed paw fell gradually and reached equilibrium within 10 minutes. The application of the rolling rods markedly narrowed the range of fluctuation of paw surface temperatures at the equilibrium, and increased the temperature difference between inflamed and noninflamed paws. We compared local hyperthermia and swelling of inflamed paws, and tested the effects of indomethacin. The results suggest that the local hyperthermia is a useful index of inflammation and a sensitive parameter for the pharmacological evaluation of antiinflammatory drugs.