Establishment of evaluation method for endurance capacity in mice

Abstract

Background: There is growing demand for evaluation of the effects of supplements on endurance capacity or physical fatigue. In many cases, this has been conducted by the treadmill test or forced swimming test for rodents, in which the time until fatigue is recorded. However, there are some problems, including the large variation of data, the excessive stress on experimental animals and the unpredictable finish time of each test. In this study, we attempted to establish a new evaluation method for endurance capacity in mice. Methods: Seven-week-old FVB mice were subjected either to a sedentary existence or forced wheel-running (1h/day) with and without a doping drug, including darbepoetin alfa (DPO: 10 μg/kg/week) and clenbuterol (CLE: 2 mg/kg/day), for 4 weeks. At 2 and 4 weeks treatment, we subjected mice to a forced swimming test, using a counter current swimming pool, in which the number of times that mice passed at a distance 35 cm from nozzle was counted every 10 min for 30 min. Results: FVB mice showed high compliance to the forced exercises, which was associated with the small variation of data. In all tested groups, the number of times at a distance 35 cm was most frequently in the first 10 min and decreased timedependently. Exercise training significantly prevented weight gain, but had no effect on endurance capacity. DPO treatment significantly increased hematocrit, but did not affect endurance performance. On the other hand, CLE treatment markedly decreased endurance capacity. Conclusions: We could evaluate the physical fatigue by counting the number of times at a distance 35 cm. The fixed duration of each test alleviated a burden on experimental animals and researchers. The results of DPO and CLE on endurance capacity were unexpected, but not inconsistent with previous reports. Therefore, our new method was considered to be useful for the evaluation of endurance capacity of mice.