7/17/2019 Histamine Bioactivity (Receptors) 2015

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Bioactivity

Smooth muscleVia H1 receptors, contracts smooth muscle of bronchi, bronchioles, ileum,

uterus

reduces flow of air during 1st phase of bronchial asthma

Cardiovascular 

Via H1 receptors, dilates blood vessels

Via cardiac H2 receptors, increases rate and cardiac output

Gastrointestinal tract (GIT)

Via H2 receptors, stimulates secretion of gastric acid

Central nervous system (CNS)

Neurotransmitter  Excitatory via H1 and H2 receptors;

Inhibitory (inhibits its own neuronal synthesis and release) via H3 receptor.

stimulates sensory nerve endings, causing itching (via H1/H4 receptors)

Pathogenesis of peptic ulcer 

Mediator of Type 1 hypersensit ivity reactions e.g. Urticaria and hayfever 

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Reference is made to Copyright Regulation 1969 on first page

HISTAMINE