Histamine Receptor

Histamine receptors are 7-transmembrane receptors which mediate cellular responses to the biogenic amine histamine. Histamine may be released as a transmitter in neuronal preparations or as a mediator of an inflammatory response by mast cells. Currently, four histamine receptors have been identified. H₁ receptors couple to Gq which regulates Ca⁺⁺ mobilization, H₂ receptors couple to Gs to stimulate cyclic AMP, and H₃ and H₄ receptors both couple to Gi/o to inhibit cyclic AMP accumulation. Histamine receptors are widely distributed in the body, with one or more receptors expressed to significant levels in neuronal, smooth muscle (vascular, gastric and bronchial), blood, heart, immune system and endocrine system.