Histamine receptors

The histamine receptors are a class of G-protein coupled receptors with histamine as their endogenous ligand.

There are four known histamine receptors:
 * The H1 receptor
 * The H2 receptor
 * The H3 receptor
 * The H4 receptor

There are several splice variants of H3 present in various species. Though all of the receptors are 7-transmembrane g protein coupled receptors, H1 and H2 are quite different from H3 and H4 in their activities. H1 causes an increase in phosphoinositol hydrolysis, H2 stimulates gastric acid secretion, and H3 mediates feedback inhibition of histamine.