<P> The H receptor is a histamine receptor belonging to the family of rhodopsin - like G - protein - coupled receptors . This receptor is activated by the biogenic amine histamine . It is expressed in smooth muscles , on vascular endothelial cells , in the heart , and in the central nervous system . The H receptor is linked to an intracellular G - protein ( G ) that activates phospholipase C and the inositol triphosphate ( IP3 ) 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 H receptor ligands in structure - based virtual screening studies . </P>
where are h1 receptors found in the body
smooth muscles vascular endothelial cells the heart the central nervous system