Histamine H1 receptor and Histamine H2 receptor (H1R and H2R)

The Histamine H1 and H2 receptors are distinct G protein-coupled receptors (GPCRs) that mediate the diverse physiological effects of histamine across different organ systems. The H1 receptor (HRH1) is heavily involved in the pathophysiology of allergic diseases, where its activation leads to increased capillary permeability, vasodilation, and bronchoconstriction (UniProt P35367). In contrast, the H2 receptor (HRH2) is the primary regulator of gastric acid secretion in the stomach and also influences heart rate and immune modulation (UniProt P25021). Clinically, H1 antagonists are the mainstay for treating allergic rhinitis and chronic urticaria, while H2 antagonists are widely used to manage acid-peptic disorders such as GERD and peptic ulcers (StatPearls, 2023). These two receptors utilize different intracellular signaling pathways, with H1 typically signaling through Gq/11 to activate phospholipase C and H2 signaling through Gs to stimulate adenylyl cyclase (PubMed, 2021). This entry is considered incorrect as a single target because it combines two genetically and pharmacologically distinct proteins into one query.

Other names

HRH1HRH2H1 receptorH2 receptorHistamine receptor H1Histamine receptor H2H1RH2R

H1 receptor antagonists primarily function as inverse agonists that stabilize the inactive state of the H1 receptor, thereby inhibiting histamine-mediated vascular permeability and smooth muscle contraction (PubMed, 2022). H2 receptor antagonists competitively inhibit histamine binding to H2 receptors on gastric parietal cells, which reduces intracellular cAMP levels and subsequently suppresses both basal and stimulated gastric acid secretion (StatPearls, 2023).