Quantitative Light Microscopic Autoradiography of 2-Adrenergic Radioligand Binding Sites

Adrenergic receptors (ARs) belong to the family of G-protein-coupled receptors and can be classified into three subfamilies, with each one having at least three distinct subtypes (1 ). Although all three subfamilies have similar affinity for the endogenous ligands norepinephrine and epinephrine, they can be characterized by their different pharmacological profiles, which was the first evidence for receptor heterogeneity, prior to the molecular cloning of nine different adrenergic receptor genes (2 ).