SWIMMING CAPACITY OF MICE IS INCREASED BY ORAL-ADMINISTRATION OF A NONPUNGENT CAPSAICIN ANALOG, STEAROYL VANILLYLAMIDE

Intravenous injection of stearoyl vanillylamide (C-18-VA), a nonpungen t capsaicin (CAP) analog, enhances adrenaline secretion significantly and as effectively as CAP in rats. Because swimming capacity was enhan ced by CAP in mice due to CAP-induced adrenal catecholamine secretion, we investigated the effects of oral administration of C-18-VA on swim ming capacity using an adjustable-current water pool. Male Std ddY 6-w k-old mice were fed a commercial diet for this study and one group was orally administered C-18-VA via a stomach tube. Treated mice were abl e to swim longer before exhaustion than the control mice (62.9 +/- 5.6 vs. 49.6 +/- 7.0 min, P < 0.05). The swimming capacity of two groups administered C-18-VA (0.02 and 0.033 mmol/kg) was significantly greate r than that of those administered vehicle alone, (P < 0.05). Substance P concentration in cerebrospinal fluid, which is involved in pain tra nsmission and is the first direct measure of pungency, was not affecte d by C-18-VA administration. In an experiment examining the effects of C-18-VA on serum adrenaline concentration, adrenaline was significant ly greater in C-18-VA treated mice than in controls at 2-h post-dose ( C-18-VA group, 26.09 +/- 2.82; control group 13.29 +/- 0.96 mu g/L, P < 0.01). In a separate study free fatty acids in serum were elevated i n treated mice at 2-h post-dose (P < 0.01). While serum glucose concen tration was not affected. These results suggest that C-18-VA increased swimming capacity of mice via adrenaline release, independent of pung ency. In addition, the present study suggests the usefulness of its ap plication to humans.