Histamine/PG Flashcards
- endogenous substances in the body (histamine, serotonin, peptides, prostaglandins, leukotrienes)
- short duration of action and act near site of synthesis/release
- high levels cause undesirable effects
autacoids
- in basophils/mast cells: high levels in potential sites of injury, nose/mouth/feet, blood vessels
- in brain : neurotransmitter function
- ECL cells in stomach: activate acid production
histamine
immunologic histamine release - allergens cross link ______ on the cell surface eliciting granulation
-releases histamine causes type ____ allergic reaction (hay fever, acute urticaria)
IgE
type 1
in CV system, H1 receptor mediated response is vasodilation mediated by increase in _______ release, reflex tachycardia, and increased _______ of post capillary vessels
NO
permeability
effect of H1 on bronchiolar smooth muscle?
bronchoconstriction
effect of H1 on GI smooth muscle?
contraction, high doses produce diarrhea
- rapidly absorbed when taken orally
- distribute to most tissues
- 1st gen last 4-6 hrs, 2nd gen last 12-24 hours
- used for allergic reactions (not bronchial asthma)
- motion sickness, sedative effects
antihistamines
- have local anesthetic action (Na channel blockers)
- diphenhydramine and promethazine more potent than procaine
- also antiparkinsonian, anticholinergic, adrenregic blocking, serotonin blocking
H1 antagonists
- sedation
- antimuscarinic - urinary retention, blurred vision
- CYP450 inhibition (ketoconazole)
H1 antagonist toxicity
- at higher doses get cAMP dependent vasodilation and direct cardiac stimulation
- increased contractility and pacemaker
- antagonists have little effect on cardiac function
H2 mediated response
-stimulate parietal cells to secrete gastric acid
H2 receptor mediated response
- ranitidine, cimetidine, nizatidine, famotidine
- reduce gastric acid secretion - peptic ulcer, GERD
- effective doses don’t impact intestinal secretion, other H2 peripheral effects (HR)
H2 antagonists
-nervous system: presynaptic receptor activation modulates nuerotransmitter release
H3 mediated response
- family of oxygenation products of polyunsaturated LCFAs
- highly potent molecules, very short half life
eicosanoids
- converts arachidonic acid to prostaglandins
- constitutively expressed, widely distributed, has housekeeping functions
COX-1
- converts AA to prostaglandins
- inducible, production of inflammatory molecules, expressed in vascular endothelium (PGI2)
- renal isozyme essential for normal function
COX-2
all eicosanoid receptors are _______
G-protein coupled
TXA2 and PGF in vascular smooth muscle?
vasoconstrictor