INCREASE IN SWIMMING ENDURANCE CAPACITY OF MICE BY CAPSAICIN-INDUCED ADRENAL CATECHOLAMINE SECRETION

Increase in endurance swimming capacity caused by capsaicin (CAP), a p ungent component of red pepper, -induced increase of fat metabolism in mice was investigated using an adjustable-current water pool, The mic e administered CAP via a stomach tube, showed longer swimming time unt il exhaustion than the control group of mice, in a dose-dependent mann er. The maximal effect was observed at a dose of 10 mg/kg while more t han 15 mg/kg had no effect, The increase of endurance was observed onl y when CAP was administered two hours before swimming. After the admin istration of CAP, the serum glucose concentration rapidly increased an d then decreased within 60 min, while the concentration of serum-free fatty acids gradually increased through 3 hours, The residual glycogen concentration of the gastrocnemius muscle after 30 min of swimming wa s significantly higher in the CAP-administered mice than in control mi ce, suggesting that use of the serum free fatty-acids spaced muscle gl ycogen consumption. The serum adrenaline concentration significantly I ncreased with twin peaks at 30 min and two hours after administration of CAP, An experiment using adrenalectomized mice was done to confirm that the effect of CAP if due to increased energy metabolism through t he secretion of adrenaline from the adrenal gland. The swimming endura nce capacity of the adrenalectomized mice was not increased by CAP adm inistration, although adrenaline injection induced a 58% increase in t he endurance time, These results suggest that the increase of swimming endurance induced by CAP in mice is caused by an increase in fatty ac id utilization due to CAP-induced adrenal catecholamine secretion.