Flashcards in 43 Serotonin Deck (18)
Where is the storage of serotonin?
platelets, neurons, GI tract in enterochomaffin cells
Do carcinoid tumors enhance release of serotonin?
What increases enterochomaffin release of serotonin?
mechanical stimulation, hypertonicity, NOR, vagal
What type of receptors are the 5HT receptors?
all are GPCR except 5HT-3 which is ligand gated ion channel
How does 5 HT 1 a,b, e, f acts in what way?
decrease ad. cyclase, Gi/o coupled
***5HT1A incr. AD. cylase in heart only
How does 5 HT 1 D acts?
up PLC, Up NO, G q coupled
How does 5 ht 2 ABC act?
up PLC up CA2, Gq coupled
What are the cardiovascular actions of 5 HT2 receptors?
1. direct vasoconstriction of vascular smooth muscle
2. platelet aggregation
What are the CV effects of 5 HT1 receptors?
1. indirect vasodilation- receptors on sympathetic neurons inhibit release of vasoconstrictor NOR
2. endothelial receptors promote release of vasodilator NO and prostaglandins
What does 5 HT3 receptor mediated activation lead to?
reflex bradycardia due to stimulation of sensory nerve endings--> inhibition of SNA and increased activity of cardiac vagus nerve
What are the smooth muscle actions of serotonin?
contracts GI and bronchiolar
[diarrhea associated with carcinoid syndrome due to effects on GI smooth muscle]
What are 5HT3 and 4 receptors therapeutic for
nausea, emesis, and bowel disorders
IS cyproheptadine an H1 antagonist too?
Yes--so side effects are drowsiness and GI disturbances
What other receptors do ketansein block?
alpha 1 adrenergic- on VSM
T-F- ergot alkaloids have both agonist and antagonist actions?
What is the mechanism of serotonin receptor agonist triptans?
1. activation of pre junctional 5HT receptors on sensory nerves resulting in blockade of trigeminovascular system--> inhibited release of inflammatory peptides
2. vasoconstriction secondarily, via 5HT 1 D receptors in cranial blood vessels
Which triptan is more lipophilic, rapidly absorbed, and has a longer half life?