Swimming Capacity of Mice Is Increased by Oral Administration of a Nonpungent Capsaicin Analog, Stearoyl Vanillylamide

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Abstract
Intravenous injection of stearoyl vanillylamide (C18-VA), a nonpungent capsaicin (CAP) analog, enhances adrenaline secretion significantly and as effectively as CAP in rats. Because swimming capacity was enhanced by CAP in mice due to CAP-induced adrenal catecholamine secretion, we investigated the effects of oral administration of C18-VA on swimming capacity using an adjustable-current water pool. Male Std ddY 6-wk-old mice were fed a commercial diet for this study and one group was orally administered C18-VA via a stomach tube. Treated mice were able 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 C18-VA (0.02 and 0.033 mmol/kg) was significantly greater than that of those administered vehicle alone, (P < 0.05). Substance P concentration in cerebrospinal fluid, which is involved in pain transmission and is the first direct measure of pungency, was not affected by C18-VA administration. In an experiment examining the effects of C18-VA on serum adrenaline concentration, adrenaline was significantly greater in C18-VA treated mice than in controls at 2-h post-dose (C18-VA group, 26.09 ± 2.82; control group 13.29 ± 0.96 μg/L, P < 0.01). In a separate study free fatty acids in serum were elevated in treated mice at 2-h post-dose (P < 0.01). While serum glucose concentration was not affected. These results suggest that C18-VA increased swimming capacity of mice via adrenaline release, independent of pungency. In addition, the present study suggests the usefulness of its application to humans.