Abstract
1 Three strains of rats spontaneously hypertensive (HRS), normotensive (NS) and hypotensive (HOS), were selected by repeated inbreeding. 2 In order to explain the different blood pressure levels observed, we have studied their vascular reactivity to noradrenaline and angiotensin II. Experiments were performed in anaesthetized ganglion-blocked, vagotomized rats. 3 The reactivity to noradrenaline was significantly higher in HRS than in NS and HOS rats. 4 The reactivity to angiotensin II appeared identical in the three strains used.