Serotonergic Neurotransmission

Question 1

90% of serotonin is found where?

Answer 1

The gut

Question 2

How is serotonin synthesised and broken down?

Answer 2

Tryptophan > Tryptophan hydroxyls (rate limiting step) > 5-hydroxytryptophan > L-aromatic acid decarboxylase (L-DOPA decarboxylase) > 5-HT (serotonin) > Monoamine Oxidase > 5-hydroxyindole acetaldehyde (maybe not there) > Adehyde dehydrogenase > 5-hydroxyindoleacetic acid (5-HIAA)

Question 3

Receptor 5HT1A is found where in the brain?

Answer 3

The brain stem, hippocampus, hypothalamus, amygdala and entorhinal cortex.

Question 4

Prader-Willi syndrome is caused by the truncation of which serotonin receptor?

Answer 4

5HT2C receptor - reducing cell surface expression

Question 5

Anti-depressants have what effect on forced swim test?

Answer 5

Decrease immobility time and increase latency to first period of immobility.

Question 6

What behaviour would you expect of a depressed mouse in the sucrose preference test?

Answer 6

Reduced preference for sucrose

Question 7

What effect do anti-depressants have on depressive animals in the sucrose preference test?

Answer 7

They increase sucrose preference in depressed animals but not in healthy animals (i.e. doesn’t induce a ‘sweet tooth’)

Question 8

How would anti-depressants affect a mouse’s behaviour in a self administration assay?

Answer 8

Pre-treatment with fluoxetine reduces the reinforcing effect of cocaine, for example.

Question 9

What does an increased or decreased breakpoint mean in the progressive ration assay?

Answer 9

Increased breakpoint = more motivated
Decreased breakpoint = less motivated
Breakpoint is when the reward is no longer worth effort