Serotonin Flashcards
(20 cards)
What is serotonin also known as?
5-hydroxytryptamine (5HT).
Where is the majority of the body’s serotonin located?
90% of the body’s serotonin is located in the gastrointestinal tract, specifically in enterochromaffin cells.
What is the biosynthetic pathway of serotonin?
Tryptophan → 5-Hydroxytryptophan → 5-Hydroxytryptamine (Serotonin) → 5-Hydroxyindoleacetic acid (5HIAA).
What indicates hypersecretion of serotonin?
Elevated levels of 5-HIAA in the urine.
How do platelets interact with serotonin?
Platelets take up serotonin from the blood and store it in granules but do not synthesize it.
Can serotonin cross the blood-brain barrier?
No, serotonin cannot cross the blood-brain barrier, so it must be synthesized de novo in the brain.
What type of receptor is 5HT3?
5HT3 is a ligand-gated ion channel (not a G protein-coupled receptor like other 5HT receptors).
What is the function of 5HT1A and 5HT1D receptors?
They are inhibitory autoreceptors involved in feedback inhibition of serotonin release.
What is the clinical relevance of 5HT1D agonists like sumatriptan?
Used in migraine treatment due to their vasoconstrictive properties on cranial blood vessels.
Where are 5HT3 receptors found and what is their function?
Found in vagal/splanchnic afferents, nucleus tractus solitarius, and area postrema; involved in emesis.
What does serotonin do in the CNS?
Acts as both a neurotransmitter and neuromodulator, affecting mood, sleep, appetite, and aggression.
How does serotonin contribute to platelet aggregation?
Via 5HT2A receptors on platelets and vascular smooth muscle, promoting aggregation and vasoconstriction.
How is serotonin involved in carcinoid syndrome?
Overproduction by enterochromaffin tumors causes flushing, diarrhea, bronchospasm, and hypotension.
What drugs are used to treat serotonin-related carcinoid syndrome?
Fenclonine (inhibits synthesis), Cyproheptadine (blocks 5HT and H1 receptors).
What is the role of 5HT4 receptors in the gut?
They promote peristalsis by enhancing motility through action on the myenteric plexus.
Which drug inhibits serotonin reuptake and is used as an antidepressant?
Fluoxetine (a selective serotonin reuptake inhibitor, SSRI).
What is the role of serotonin in the Bezold-Jarisch reflex?
It causes bradycardia and hypotension via stimulation of 5HT3 receptors on the vagus nerve.
What is the mechanism of action of ondansetron?
It is a 5HT3 antagonist used to treat nausea and vomiting.
What is the proposed role of serotonin in migraines?
Serotonin causes vasoconstriction and perivascular inflammation, contributing to migraine pathophysiology.
What are common serotonergic drugs used in migraine treatment?
Sumatriptan, ergotamine, aspirin.
