5-HT

Question 1

How and where is 5HT synthesised?

Answer 1

synthesised from dietary amino acid tryptophan
Tryptophan hydroxylase is the rate limiting step
Then enzyme L-amino acid decarboxylase
= 5HT

Question 2

How is 5HT reuptaken?

Answer 2

by SERT back to the presynaptic terminal

a high affinity uptake mechanism

Question 3

Serotonin is degraded by what process/enzymes?

Answer 3

Monoamine oxidase (MAO)
Aldehyde dehydrogenase

Question 4

List the location of serotonin pathways in the brain

Answer 4

Raphe nuclei (dorsal raphe) projections

Question 5

List some of the functions served by 5HT on the CNS

Answer 5

Regulation of mood (low tryptophan = symptom relapse in depression)
Role in aggression (high 5HT decreases aggression, low levels increases aggression)
Role in learning and memory

Question 6

What type of diet is likely to increase the rate of 5HT synthesis?

Answer 6

High carb, low protein diet

Question 7

What derivative does 5HT come from?

Answer 7

Tryptophan

Question 8

Rate limiting step in 5HT synthesis

Answer 8

Tryptophan hydroxylase = rate limiting step

Question 9

What happens to 5HT once synthesised?

Answer 9

5HT is transported into vesicles by VMAT2

Question 10

What type of receptors does serotonin act on

Answer 10

All GPCR except 5HT-3 receptor = ligand gated catION channel

Question 11

What is SERT and what is its function

Answer 11

Serotonin reuptake transporter

Function: high affinity uptake mechanism

Question 12

What is the degradation product of 5HT?

Answer 12

5-HIAA

Question 13

5HT3 receptor role

Answer 13

Vomiting reflex

Question 14

5HT2 receptor role

Answer 14

2a subtype - involved in higher level functions (in cerebral cortex)

Question 15

5HT1 receptor role

Answer 15

Mainly inhibitory role, regulation of mood and behaviour

1a subtype = hippocampus, septum, amygdala, raphe nuclei