lecture 4 histamine Flashcards
(24 cards)
histamine
released by mast cells when an allergen is encountered. derived from histidine
mast cells
release histamine
H2 receptor
histamine receptor, coupled to Gs, producing cAMP
H1 receptor
can bind released histamine, coupled to Gq
C3a/C5a receptors
complement activation when there is inflammation
IgE receptor
can increase calcium in mast cell when agonist binds
H3 receptor
presynaptic autoreceptor, coupled to Gi
triple response
caused by H1 receptor in endothelial cells, they shrink causing oedema
cromoglicic acid/cromoglycine
inhibits calcium release influx in mast cells
omaluzimab
inhibits IgE
Beta agonist
activating B2 receptor
zileuton
inhibits LOX
montelukast
inhibits leukotrienes
H1 receptor antagonists
anti allergic effects, 2nd generation compounds are used
H2 receptor antagonists
inhibition of gastric acid production
H3 receptor antagonists
increases alertness
cimetidine, ranitidine and famotidine
H2 receptor antagonist. inhibition of gastric acid production
functions of H1 receptors
e.g. contraction smooth muscle cells, stimulation endothelial cells and stimulation of CNS. Functions might cause side effects
diphenhydramine
1st generation H1 receptor antagonist, causes sedation, hypnotic effect. also blocks muscarinic receptors
promethazine
1st generation H1 receptor antagonist, same side effects as diphenhydramine, but also blocks dopamine causing weak neuroleptic effect
terfenadine and astemizole
2nd generation H1 receptor antagonist. not used due to severe side effects like cardiac arrest
loratidine, desloratidine and cetrizine
2nd generation H1 receptor antagonist, still used
anaphylactic shock
enormous histamine concentrations, causing swelling of the face and throat, treated with adrenaline
pitolisant
H3 receptor antagonist, increases alertness, used for narcolepsy
