(MRI-0.5, Nichon-Kogden, Japan) on both carotid arteries. The maximum dp/dt and electro- cardiogram were recorded on a RM-6000 polygraph (Nichon-Kogden). Test compounds were dissolved in 50% dimethylacetamlde and injected intravenously (0.05 ml/kg) through a cannule in the femoral vein. In tests on stimulated spontaneously hypertensive male rats weighing 180-220 g (Okamoto- Aoki strain) [8] aged 7-12 months the arterial systolic pressure was measured ...