Alpha-1 adrenergic receptor (ADRA1) (ADRA1)

The Alpha-1 adrenergic receptor is a G protein-coupled receptor (GPCR) that plays a central role in the sympathetic nervous system's regulation of vascular tone. It is the primary molecular target for decongestant medications, which are used to treat nasal congestion associated with allergies and upper respiratory infections (StatPearls, 2023). These receptors are highly expressed on the smooth muscle cells of the blood vessels in the nasal mucosa. Activation of these receptors by agonists leads to vasoconstriction, which reduces the swelling of the nasal membranes and decreases mucus production, thereby improving nasal airflow (NIH, 2023). Beyond the respiratory system, Alpha-1 receptors are involved in maintaining systemic blood pressure and regulating the contraction of smooth muscle in the prostate and eye (PubChem, 2024). Because of their widespread distribution, drugs targeting these receptors can cause systemic side effects such as elevated blood pressure and heart rate. Prolonged use of topical decongestants can lead to receptor down-regulation and a phenomenon known as rebound congestion or rhinitis medicamentosa (PubMed, 2022).

Other names

Alpha-1 adrenoceptorAlpha-1 adrenoreceptorAdrenoceptor alpha 1Decongestant target

Decongestants act as agonists of the Alpha-1 adrenergic receptor. Binding to the receptor activates the Gq protein-coupled signaling pathway, which stimulates phospholipase C (PLC). PLC cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 triggers the release of calcium from the sarcoplasmic reticulum, leading to smooth muscle contraction and vasoconstriction of the nasal mucosal blood vessels (StatPearls, 2023; UniProt, 2024).