Interactions of Sympathomimetic and Sympatholytic Agents in Normotensive and Hypertensive Subjects

Sympathomimetic agents and their blocking agents were administered drop-wise intravenously alone or in various combinations to 9 normotensive subjects and 16 patients with essential hypertension. Their effects on the cardiovascular reaction (heart rate and blood pressure) were compared in order to estimate the degree of stimulation of α- and β-receptors respectively. When the α- and β-receptor stimulating effects of so-called α- and β-receptor stimulators were completely blocked by corresponding blocking agents respectively, β-effect in the α-stimulator and a-effect in the β-stimulator remained in effect without any modification in the degree of responses. Simultaneous injection of a-stimulator and β-blocker caused no change in the heart rate (β-effect), but produced additive increase in the blood pressure (α-effect) already raised by single treatment of the α-stimulator. A similar additive effect was observed also in the β-effect when β-stimulator and α-blocker were injected simultaneously. Such an increase in the α- or β-effect seemed to be due to conversion of β- or α-effect blocked by β- or α-blocker respectively, but it was not attributable to the α-or β-effect of the blockers themselves. The β-effect induced in this way, that is, the reactivity of α-receptor was greater in hyperensive patients than in nor-motensives, and the β-effect induced in the same way was greater in normotensives than in hypertensive patients.