Histamine receptor

Histamine receptor is a class of G protein-coupled receptors which bind histamine as their primary endogenous ligand. There are four known histamine receptors: H1 receptor, H2 receptor, H3 receptor, and H4 receptor. Each of these receptors has a unique role in various physiological functions.

H1 receptor[edit | edit source]

The H1 receptor is found in smooth muscle, endothelial cells, and central nervous system tissue. It is involved in inflammatory responses, and its activation results in effects such as vasodilation, bronchoconstriction, smooth muscle activation, and separation of endothelial cells (which can cause hives).

H2 receptor[edit | edit source]

The H2 receptor is located on parietal cells, primarily in the stomach. Activation of the H2 receptor results in gastric acid secretion. H2 receptor antagonists are commonly used to relieve the symptoms of conditions such as peptic ulcers and gastroesophageal reflux disease (GERD).

H3 receptor[edit | edit source]

The H3 receptor is primarily found in the central nervous system and to a lesser extent, the peripheral nervous system. It is involved in the inhibition of the release of histamine and other neurotransmitters such as acetylcholine, serotonin, and norepinephrine.

H4 receptor[edit | edit source]

The H4 receptor is found primarily in bone marrow and white blood cells. It is involved in the chemotaxis and cellular activation of mast cells, eosinophils, and T cells.

Antagonists[edit | edit source]

Histamine receptor antagonists, also known as antihistamines, are drugs that bind to these receptors but do not activate them. This action prevents histamine from binding and exerting its effects. Antihistamines are commonly used to treat conditions such as allergies and gastric ulcers.