Serotonin Flashcards
Where can serotonin be found in nature? (3 items)
- Plants
- Invertebrate venoms
- Vertebrate physiology
What essential amino acid is serotonin derived from?
Tryptophan
What is the rate limiting step of Serotonin synthesis?
Tryptophan hydroxylase
What limits the synthesis of Serotonin in the brain?
Tryptophan concentration
What similar enzyme to Tryptophan hydroxylase is used for catecholamine synthesis?
L-aromatic amino acid decarboxylase
Where is Serotonin converted to melatonin?
Pineal gland
What is Serotonin metabolized to?
By what enzyme?
5-hydroxyindole by
Monoamine oxidase
How is serotonin related neuronal action terminated?
SERT - high affinity active uptake system
Once serotonin is taken back up into the neuron to terminate neuronal action, what is it converted to?
5-hydroxyindoleacetic acid
Where is Serotonin located in the body and in what percentages? (3 items)
- GI System - 90%
- Platelets - 8%
- CNS - 2%
What is different about presence of Serotonin in platelets vs. GI or CNS?
Platelets cannot synthesize Serotonin
Where are the cell bodies of neurons that produce Serotonin in the CNS?
Midbrain - raphe nuclei
Is turnover of Serotonin in the brain fast or slow?
Fast - < 4 hours
Most serotonin receptors are _____ receptors.
G-protein coupled
5-HT1 A-E receptors have what type of molecular activity?
Inhibition of adenylate cyclase
5-HT1 A has what secondary activity besides inhibiting adenylate cyclase?
It opens K+ channels
5-HT2 A-C receptors have what type of molecular activity?
Phosphatydil Inositol hydrolysis (DAG/IP3/Ca+ system)
5-HT3 receptors have what kind of molecular activity?
Open ligand-gated Cation channel
5-HT4-7 receptors have what kind of activity?
Activation of adenylate cyclase
Serotonin auto-receptors do what?
Decrease serotonin release
Is turnover of GI system synthesis and storage fast or slow?
Slow ~1day
What action does serotonin release have on GI smooth muscle?
What symptomatic effect does this create?
Contraction of GI smooth muscle in esophagus, stomach, and intestine
This increases tone, peristalsis and diarrhea
Which receptor stimulates emesis and where is it located?
5-HT3 in GI tract and brain
What is the relationship of Carcinoid syndrome (enterochromaffin cell tumors) and serotonin?
They secrete serotonin and bradykinin causing diarrhea and asthma
What effect does Serotonin have on large arteries and veins?
Potent vasoconstriction
What effect does Serotonin have on cranial blood vessels and by what receptor?
Vasoconstriction by the 5-HT1D receptor
What effect does Serotonin have on Coronary, skeletal muscle, and cutaneous blood vessels?
Vasodilation