The H₁ receptor is a histamine receptor belonging to the family of Rhodopsin-like G-protein-coupled receptors. This receptor, which is activated by the biogenic amine histamine, is expressed throughout the body, to be specific, in smooth muscles, on vascular endothelial cells, in the heart, and in the central nervous system. The H₁ receptor is linked to an intracellular G-protein (G_q) that activates phospholipase C and the phosphatidylinositol (PIP2) signalling pathway. Antihistamines, which act on this receptor, are used as anti-allergy drugs. The crystal structure of the receptor has been determined (shown on the right) and used to discover new histamine H₁ receptor ligands in structure-based virtual screening studies.

The H₁ receptor is a histamine receptor belonging to the family of Rhodopsin-like G-protein-coupled receptors. This receptor, which is activated by the biogenic amine histamine, is expressed throughout the body, to be specific, in smooth muscles, on vascular endothelial cells, in the heart, and in the central nervous system. The H₁ receptor is linked to an intracellular G-protein (G_q) that activates phospholipase C and the phosphatidylinositol (PIP2) signalling pathway. Antihistamines, which act on this receptor, are used as anti-allergy drugs. The crystal structure of the receptor has been determined (shown on the right) and used to discover new histamine H₁ receptor ligands in structure-based virtual screening studies.