The beta-2 adrenergic receptor (β2 adrenoreceptor), also known as ADRB2, is a cell membrane-spanning beta-adrenergic receptor that interacts with (binds) epinephrine, a hormone and neurotransmitter (ligand synonym, adrenaline) whose signaling, via a downstream Ltype calcium channel interaction, mediates physiologic responses such as smooth muscle relaxation and bronchodilation. Unlike other adr...