<Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> </Table> <Tr> <Td_colspan="2"> View / Edit Human </Td> <Td_colspan="2"> View / Edit Mouse </Td> </Tr> <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> <P> The expression of NF - κB, the transcription factor that regulates inflammatory processes, is promoted by the constitutive activity of the H receptor as well as by agonists that bind at the receptor . H - antihistamines have been shown to attenuate NF - κB expression and mitigate certain inflammatory processes in associated cells . </P>

Where are h1 receptors found in the body