Histamine receptors

 There are 4 sub-classes of Histamine receptor:

H1 receptor
H2 receptor
H3 receptor
H4 receptor

Different receptor sub-classes mediate different responses when bound by Histamine, as each receptor type is localised to a particular body compartment. Histamine receptors are G-protein coupled receptors and are the primary target of Histamine anatgonists in the treatment of allergies, peptic ulcers, and some neurological diseases.