Alpha-2 adrenergic receptor (α2-AR) (α2-AR)

The alpha-2 adrenergic receptor (α2-AR) is a G protein-coupled receptor that mediates the physiological responses to the catecholamines norepinephrine and epinephrine. In the nasal cavity, these receptors are expressed on the smooth muscle of the vasculature, including both resistance arteries and the large venous sinusoids that comprise the erectile tissue of the nasal mucosa (PubMed, PMID: 2853464). Activation of α2-ARs by sympathomimetic agonists leads to potent vasoconstriction, which reduces the volume of the nasal mucosa and decreases airway resistance, providing rapid relief from nasal congestion (StatPearls, 2023). This target is the primary site of action for many over-the-counter topical decongestants used to treat symptoms of allergic rhinitis and the common cold. However, the therapeutic use of α2-AR agonists is limited by the risk of rhinitis medicamentosa, a rebound phenomenon where the nasal mucosa becomes chronically congested due to receptor down-regulation and loss of vascular tone (PubMed, PMID: 15903148). Additionally, systemic absorption of these drugs can lead to cardiovascular side effects, such as hypertension or bradycardia, particularly in vulnerable populations.

Other names

Alpha-2 adrenoceptorα2-adrenoreceptorADRA2Alpha-2 adrenergic receptor

Agonism of alpha-2 adrenergic receptors on nasal vascular smooth muscle leads to Gi protein activation, inhibition of adenylyl cyclase, and subsequent vasoconstriction, reducing mucosal swelling (StatPearls, 2023).