Ingestion of bonito extract ameliorates peripheral blood flow in mice loaded from over crowding stress

Bonito extract (BE) has been shown to improve various fatigue-related symptoms. The possibility that the improvement of blood flow contributes to the improvement of fatigue-related symptoms has been reported. However, even though BE has been found to increase peripheral blood flow in humans, an understanding of its mechanisms has remained elusive. The purpose of the present study is to construct an animal model system with which the blood flow-increasing effects of BE can be examined. Using mice loaded with crowding stress, an attempt was made to reproduce the increases in peripheral blood flow observed in humans after a single administration of BE. In this study, the crowded-condition mice (20 mice/cage) showed significantly increased catecholamine levels (noradrenaline, adrenaline, and dopamine) in their circulating blood and a decreased rate of skin blood perfusion in comparison with the normal-condition mice (6 mice/cage). The rate of skin blood perfusion was significantly increased by BE in the crowded-condition mice in comparison with the controls, but not influenced by BE in the normal-condition mice. This suggests that BE expands the vascular diameter by affecting the constriction of vessels induced by catecholamines.