Histamine Agonists Flashcards
How are histamine agonists formed
Decarboxylation of L-histidine
What kind of receptors do they bind
G protein
G protein for H1
Gq
G protein for H2
Gs
Most prominent effect of histamine agonists
Vasodilation (H1 and H2)
Where is H1 located
Endothelium, SM, nerve endings
Where is H2 located
Gastric mucosa, Cardiac muscle cells, immune cells
What is the action of H3
Reduce NT release from histaminergic and other neurons
What is the action of H4
Chemotactic for EOS and mast
On WBCs in BM and blood
Inflammation and allergies
Is the histamine receptor constitutive
Yes
What is the histamine triple response
Localized red spot
Flare
Wheal
What mediates GIT contraction and bronchconstriction
H1
CVS action of H2
Increase contractility and HR
CVS action of H1
Increase capillary permeability
Edema
Urticaria
What H receptor stimulates nerve endings causing pain and itching
H1
Which receptor mediates gastric acid secretion
H2
Clinical use of histamine
Pulmonary function testing
Histamine Contraindications
Asthmatics
Peptic ulcer disease/GI bleed
Main AE of histamine
Anaphylaxis
Immunological method of histamine release
Ag → IgE (on mast) → degranulation and release
Ca mediated
Chem/Mech method of histamine release
Morphine/Tubocurarine (amines) displace histamine from heparin complex
