Serotonin - Background

Question 1

What is another name for serotonin?

Answer 1

5-hydroxytryptamine (5-HT) - not tryptophan

Question 2

What are the steps in the synthesis of serotonin?

Answer 2

2 steps:

Hydroxylate tryptophan then decarboxylate it and you have serotonin.

Question 3

What is the rate limiting step in the synthesis of serotonin?

Answer 3

Blockage of the tryptophan 5 hydroxylase step

Question 4

What metabolizes serotonin?

Answer 4

MAO-A in the liver and in most serotonin containing tissues

Question 5

What is the main metabolite of serotonin?

Answer 5

5-HIAA (5-hydroxyindole acetic acid). They look for it in the cerebrospinal fluid to see if serotonin is being used physiologically. The pathway depends on the relative availability of NAD+ or NADH

Question 6

Where is serotonin located in the body?

Answer 6

90% in the enterochromaffin cells of the intestine
8% in platelets
2% in CNS (raphe, hypothalamus, pineal gland)

Question 7

What is serotonin a precursor of?

Answer 7

Melatonin

Question 8

What does blocking serotonin do to a person’s behavior?

Answer 8

Makes people go back into depression because serotonin reduces depression (key to controlling your mood)

Question 9

What has been found in people who have committed violent suicides?

Answer 9

Very reduced levels of 5-HIAA. They are not utilizing serotonin in the brain (the metabolite shows that they are using serotonin)

Question 10

What drug blocks Tryptophan hydroxylase (the rate limiting step in the synthesis of serotonin)?

Answer 10

Parachlorophenylalanine