Adrenegic receptor

Adrenergic receptors respond to adrenaline and noradrenaline and can be found in a variety of different tissues.

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
  

Adrenergic receptors are G-protein coupled receptors.