Antihistamines Flashcards
(53 cards)
Histamine is synthisized from histidine, and is found as granules in what two cell types?
Mast Cells
Basophils
What two body systems typically have histamine receptors?
brain, GI
Normally, histamine is complexed with proteases, heparin, or proteoglycans which ensure it is (active/inactive)
inactive storage
In the allergic reaction, T-Helper cells bind to a naive B-cell, which secretes _______ to plasma. ______ can then bind which receptors on mast cells/basophils to release histamine in the effector phase?
IgE
6 major effects of histamine
SM contraction Vasodilation vascular permeability platelet aggregation complement activation mucus secretion
IgE binds which receptors on mast cells/basophils?
Fc
An allergen forms what on which mast cell structures that results in activation?
allergen bridges IgE
The activated mast cells utilizes PK to increase concentrations of what two substances?
IP3 and Calcium
increased intracellular concentration of IP3 and Calcium activates ______, which has what 4 effects?
IP3 and Calcium activate PLA2
PLA2 increases platelet activating factor, leukotrienes, kinins, histamine release
The below have what effect on mast cells?
Contrast dyes Organic bases Morphine d-TC, Succinylcholine Many venoms Scratching, cold, sun
Cause histamine release without sensitization (IgE)
Is the itching after morphine administration an allergic response? why or why not?
no… no IgE Abs to morphine.
Morphine causes direct histamine release
What effect does the H1 receptor have on endothelium?
activates NO
H1 receptor mediates the allergic response present on what 2 tissue types?
smooth muscle
endothelium
H1 receptor has what 2 effects on the brain?
wakefullness
appetite control
What three tissue types have the H1 receptor?
smooth muscle
endothelium
brain
What three cell types have the H2 receptor?
heart, brain, mast cells
The main function of the H2 receptor…
gastric acid secretion (via cAMP)
Which histamine receptor types cause vasodilation?
H1 and H2
Which histamine receptor types cause bronchospasm?
H1
In order for H2 receptors to exert vasodilatory effects, what concentration of histamine must be present?
high concentration
What are 3 major effects of histamine mediated vasodilation?
- decreased BP + reflex tachycardia
- capillary permeability
- edema, swelling
What effect does histamine have on the skin?
causes pruritis
what is described below?
red spot via vasodilation
flare due to out axon-reflexes
wheal in 2-3 minutes due to capillary permeability
triple response
What is the first sign of histamine release?
burning/itching (esp. ears)
