Adrenergic receptors can be subdivided into two major classes: α- and β-adrenoreceptors.
For α-adrenoreceptors, the potency and affinity is noradrenaline ≥ adrenaline >> isoprenaline.
For β-adrenoreceptors, the potency and affinity is isoprenaline > adrenaline > noradrenaline.
α-Adrenoreceptors are subdivided into two subgroups, α1 and α2 receptors.
β-Adrenoreceptors are subdivided into two subgroups, β1 and β2 receptors.
Effects mediated by adrenoreceptor (when activation):
- α1: Smooth muscle contraction, vasoconstriction
- α2: Causes feedback inhibition
- β1: Increase in the rate and force of contraction of the heart
- β2: Smooth muscle relaxation, bronchodilation