Lecture 35: Serotonin Flashcards
What is the mechanism of serotonin synthesis?
Serotonin synthesized in cell body
Tryptophan 5-HTP (hydroxytryptophan) 5-HT
-tryptophan is an essential amino acid
What is the characteristic of serotonin?
It is involved in many physiological processes, but is not associated with just one!
What is serotonin?
5-hydroxytryptamin
8-10% present in platelets
80% in eneterochromaffin cells in GI track (duodenum)
20% produced in CNS
What does serotonin do to platelets?
Causes platelet aggregation via actions of 5-HT receptors
- important in clotting
- healthy vessels with 5HT lead to vasodilation
- damaged vessels with 5HT leads to constriction
What does serotonin do in GI tract?
Widespread distribution of SERT (serotonin transporter) in gut
Regulations motility and digestion of GI tract
Initiate secretory and peristaltic reflexes
Where is serotonin produced?
In nuclei of the midbrain
Primarily in the RAPHE nuclei
Caudal body cell body groups vs. rostral cell body groups
What is the inactivation process of 5-HT?
MAO degradation
What is the significance of tryptophan hydroxylase?
Rate limiting step
Tryptophan to 5-hydroxyTRYPTOPHAN (not tryptamine)
What is the significance of serotonin in the pineal gland?
It is the precursor to melatonin
What is the common byproduct of serotonin?
5-HIAA (5 hydroxyindoleacetic acid)
What are the two genes that regulate 5-HT synthesis?
By tryptophan hydroxylase periphery (Tph1)
And
Tph2 (in the brain)
Serotonin is regulated SEPARATELY in brain and periphery
What is Tph2 regulated by?
Short term: -phosphorylation leads to increased enzymatic activity -PKA -Ca/CamKII -PKC Long term: -exogenous signals (cAMP) can up or down regulate total amount of protein via gene regulation -neural activity Stress hormones and ovarian steroids
Can you increase/decrease serotonin through diet?
Yes you can through taking tryptophan hydroxylase
e.g. spaghetti
(5-HTP) is used as an aid for sleep to increase serotonin
How do you decrease serotonin?
Take drink with NEUTRAL amino acids
- takes away tryptophan
- decreases serotonin
How is serotonin stored?
Serotonin transport (SERT)
-responsible for removal of serotonin from synaptic cleft
-inhibited by SSRIs
-inhibited by fenfluramine
Vesicular monamine transporter 1 and 2
-responsible for vesicular concentration of catecholamines and serotonin
-inhibted by reserpine
-inhibted by fenfluramine
There is some evidence that people with short/short serotonin transporter has a higher risk of developing depression
What does fenfluarmine do? Significance
Blocks VMAT (vesicular monoamine transport) and SERT -this increases the active extrusion of serotonin
What are antidepressants?
Substrates for pre-synaptic transporters
-stimulates RELEASE of serotonin in synapse