5-HT (FS Week 5)

Question 1

What type of neurotransmitter is 5-HT (seretonin)

Answer 1

a monoamine neurotransmitter

Question 2

Where is serotonin found

Answer 2

in the periphery and CNS

Question 3

How is serotonin synthesised

Answer 3

from Tryptophan (which is derived from dietary sources)

Tryptophan >* 1,5-hydroxytryptophan (5-HTP) >** 5-HT

• by tryptophan hydroxylase

Question 4

How many forms does tryptophan hydroxylase have

Answer 4

2 forms

TPH2 is neuronal

Question 5

How is transport of 5-HT to the CNS regulated

Answer 5

regulated by the availability of tryptophan - which competes with larger amino acids for a single transporter - diet has an impact

Question 6

What kind of diet increases serotonin synthesis

Answer 6

low-protein

high-carb

Question 7

How is Serotonin transported into vesicles

Answer 7

VMAT2

Question 8

What are the serotonin receptors

Answer 8

5-HT1(a,b,,d,e,f) - Gi coupled
5-HT2(a,b,c)  - Gq coupled
5-HT3a - ligand gated ion channel
5-HT4- Gs coupled
5-HT5a - Gs coupled
5-HT6 - Gs coupled
5-HT7 - Gs coupled

Question 9

Detail the mechanism of 5-HT1a receptor

Answer 9

5-HT binds and causes the opening of ion channels - K+ moves out which causes hyperpolarization

It is also Gi coupled = inhibits adenylate cyclase = decrease in cAMP

Question 10

Detail the mechanism of 5-HT2a receptor

Answer 10

5-HT binds and activates protein kinase C (Gq coupled) can mobilise stores of Ca2+in the cell

Question 11

How is 5-HT taken back up into presynaptic terminal

Answer 11

by SERT

Question 12

What are some common effects if SERT is blocked

Answer 12

• anxiety
• depression
• hyperalgesia

Question 13

How is 5-HT degraded

Answer 13

degraded by:

• monoamine oxidase
• aldehyde dehydrogenase

Question 14

What is the main metabolite of 5-HT degradation

Answer 14

5-HIAA

Question 15

How can we monitor what is happening in terms of 5-HT function

Answer 15

take a urine sample to check for levels of 5-HIAA

Question 16

Where do serotonergic neurons originate from

Answer 16

the dorsal raphe located in the midbrains

Question 17

What is the role of the 5-HT1 receptor in the CNS and where is it found?

Answer 17

inhibitory - involved in regulation of mood and behaviour

Found in:

• hippocampus
• septum
• amygdala
• raphe nucleii

Question 18

What is the role of the 5-HT2 receptor in the CNS and where is it found?

Answer 18

5-HT2a found in higher level functions throughout the cerebral cortex

Question 19

What is the role of the 5-HT3 receptor in the CNS and where is it found?

Answer 19

involved in vomiting and reflex in the area postrema

Question 20

Name 5 roles of 5-HT in behaviour

Answer 20

• mood
• aggression
• feeding behaviour
• anxiety related behaviours
• learning and memory

Question 21

In terms of behaviour how is mood affected by depleted 5-HT levels

Answer 21

it can lead to depressive symptoms

Question 22

In terms of behaviour how is aggression affected by elevated 5-HT levels

Answer 22

aggression decreases

Question 23

In terms of behaviour how are feeding habits affected by elevated 5-HT levels

Answer 23

reduces appetite

Question 24

What drug can induce hypophagia (less likely to eat)

Answer 24

meta-chlorophenylpiperazine (a serotonin agonist)

Question 25

In terms of behaviour how is anxiety affected by depleted 5-HT levels

Answer 25

more anxious