Some Aspects of the Pharmacology of β-Adrenoreceptor Blockers

Abstract

The pharmacodynamic properties of a β-blocker are mainly determined by its affinity to β₁ andβ₂-receptors respectively and by its intrinsic activity. It is suggested that there is no absolute organ separation of the two receptor sub-types. Instead bothβ₁ andβ₂ -receptors are involved in the mediation of the same effect. The frequency distribution ratio of β₁/β₂-receptors varies markedly among various effector responses. A non-selective and aβ₁-selective blocker may have different haemodynamic effects when the levels of circulating adrenaline are high, because of their markedly different potency in inhibiting theβ₂-mediated vasodilator effect of adrenaline. Data are presented which suggest the existence of a presynapticβ₁ -receptor mediating a positive feedback mechanism on neuronal release of noradrenaline.