cellular action
Last reviewed 01/2018
Histamine acts via two types of target receptor:
- H1:
- activation causes an increase in cytosolic calcium
- found predominantly on smooth muscle of gut and lung where it promotes contraction; bronchial histamine has a role in asthma
- in vessels, an important role in inflammation as epitomised by the triple response:
- vasodilatation of arterioles
- vasodilatation of pre-capillary sphincters
- increased permeability of post-capillary venules
- H2:
- activation causes an increase in adenylate cyclase
- in the stomach, H2 receptors stimulate the production of acid by parietal cells
- in the heart, H2 receptors cause positive inotropy and chronotropy
It may also act indirectly, as it does in the stimulation of free nerve endings to cause pruritus.