HISTAMINE AND ITS RECEPTORS


Histamine: It is an amino acid derivative, usually secreted from the mucosal mast cells of the stomach. Histamine is produced primarily by mast cells and basophils, which are abundant in the skin, GI tract, and respiratory tract. Histamine is stored in granules in mast cells and basophils until it is released. It is found that histamine serves as the stimulator of the parietal cells to secret hydrochloric acid.

Histamine Receptors: Histamine, whether formed in the body or come from the out side, cannot perform its action until it can reaches at their specific receptors. Histamine receptors have been classified as H1, and H2, and H3

a) H1 receptor: receptors are present mainly in the smooth muscles of intestine, bronchi and blood vessels. H1 receptors are involved in allergic reactions that cause dermatitis, rhinitis, conjunctivitis, and other forms of allergy.

b) H2 receptor: receptors are mainly present in the gastric parietal cells and the smooth muscles of some blood vessels. H2 receptors are primarily concerned with gastric acid secretion but they are also involved in allergic reactions.

c) H3 receptor: These are presynaptic receptors located on nerve terminals. Activation of these receptors inhibits the release of histamine and other neurotransmitters.


Ref : PMD, OSL, Bangladesh