Comparison between plethysmometer and micrometer methods to measure acute paw oedema for screening anti-inflammatory activity in mice

The present study was undertaken to evaluate the sensitivity of the plethysmometer and micrometer, which are the most commonly employed methods to measure the paw oedema for screening anti-inflammatory agents. Acute paw swelling was induced by s.c. injection of 0.02 ml carrageenan in mice. The maximum paw oedema (59.4%) was found to be at 3.5 h after injection of carrageenan in the hind paw of mice. Oral indomethacin treatment in the dose of 5 mg/kg 1 h prior to the induction of paw oedema, caused a significant (P < 0.05) reduction in paw swelling, when the plethysmometer method was used. When the micrometer method was used to measure the paw swelling, oral indomethacin at the dose of 1 mg/kg resulted in a significant reduction in paw oedema. These findings suggest that micrometer method is more sensitive to detect the lowest antiinflammatory dose of indomethacin when compared with the plethysmometer method. The possible significance of these findings is discussed.