43 Serotonin

Question 1

Where is the storage of serotonin?

Answer 1

platelets, neurons, GI tract in enterochomaffin cells

Question 2

Do carcinoid tumors enhance release of serotonin?

Answer 2

yes

Question 3

What increases enterochomaffin release of serotonin?

Answer 3

mechanical stimulation, hypertonicity, NOR, vagal

Question 4

What type of receptors are the 5HT receptors?

Answer 4

all are GPCR except 5HT-3 which is ligand gated ion channel

Question 5

How does 5 HT 1 a,b, e, f acts in what way?

Answer 5

decrease ad. cyclase, Gi/o coupled

***5HT1A incr. AD. cylase in heart only

Question 6

How does 5 HT 1 D acts?

Answer 6

up PLC, Up NO, G q coupled

Question 7

How does 5 ht 2 ABC act?

Answer 7

up PLC up CA2, Gq coupled

Question 8

What are the cardiovascular actions of 5 HT2 receptors?

Answer 8

1. direct vasoconstriction of vascular smooth muscle

2. platelet aggregation

Question 9

What are the CV effects of 5 HT1 receptors?

Answer 9

1. indirect vasodilation- receptors on sympathetic neurons inhibit release of vasoconstrictor NOR
2. endothelial receptors promote release of vasodilator NO and prostaglandins

Question 10

What does 5 HT3 receptor mediated activation lead to?

Answer 10

reflex bradycardia due to stimulation of sensory nerve endings–> inhibition of SNA and increased activity of cardiac vagus nerve

Question 11

What are the smooth muscle actions of serotonin?

Answer 11

contracts GI and bronchiolar

[diarrhea associated with carcinoid syndrome due to effects on GI smooth muscle]

Question 12

What are 5HT3 and 4 receptors therapeutic for

Answer 12

nausea, emesis, and bowel disorders

Question 13

IS cyproheptadine an H1 antagonist too?

Answer 13

Yes–so side effects are drowsiness and GI disturbances

Question 14

What other receptors do ketansein block?

Answer 14

alpha 1 adrenergic- on VSM

Question 15

T-F- ergot alkaloids have both agonist and antagonist actions?

Answer 15

True

Question 16

What is the mechanism of serotonin receptor agonist triptans?

Answer 16

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

Question 17

Which triptan is more lipophilic, rapidly absorbed, and has a longer half life?

Answer 17

zolmitripan

Question 18

An inverse agonist of 5HT2A receptors would impair what 3 things?

Answer 18

platelet aggregation, arterial constriction, and thickening of vessel wall [maybe prevent MI and stroke]