Plasma adrenaline and noradrenaline concentrations of the spontaneously hypertensive rat

The role of the sympathetic nervous system in the mechanism of blood pressure rise in spontaneously hypertensive rats (SHR) was investigated by measuring plasma levels of adrenaline and noradrenaline in 5-week-old, 7-week-old, 6-month-old, and 12-month-old SHR. Age-matched normotensive Wistar-Kyoto rats (WKY) were used as control animals. Blood samples were collected through an indwelling catheter in a conscious state. In 5-week-old and 7-week-old SHR both plasma adrenaline and noradrenaline concentrations were significantly higher than those of WKY. In 6-month-old SHR plasma noradrenaline was significantly higher than that of WKY, while plasma adrenaline was not significantly different. In 12-month-old SHR the plasma levels of both adrenaline and noradrenaline were not different from those of WKY. This study indicated more distinct increase in plasma noradrenaline than in plasma adrenaline in young SHR, and also suggests that peripheral sympathetic activity and the adrenal medulla may play important roles in the development of hypertension in SHR.