Dopamine (FS Week 6)

Question 1

What type of neurotransmitter is dopamine

Answer 1

a catecholamine

Question 2

How is dopamine synthesised

Answer 2

derived from tyrosine an amino acid

it is regulated by tyrosine hydroxylase

tyrosine > DOPA > Dopamine > noradrenaline > adrenaline

Question 3

Where is dopamine stored

Answer 3

in vesicles

Question 4

What are the dopamine receptors dopamine acts on

Answer 4

D1 type (Gs coupled activates adenylate cyclase)
D2 type (Gi coupled inhibits adenylate cyclase)

Question 5

What happens when D1 receptors are activated

Answer 5

phosphorylates voltage gated channels and ionotropic receptors for GABA and Glutamate

Question 6

How is dopamine degraded

Answer 6

the dopamine transporter is a cot transporter of Na+, Cl- and the neurotransmitter

The NT uses the gradient of Na+ as a driving force

Once re taken up it is acted on by monoamine oxidase and catechol-O-methyltransferase

Question 7

what is the main metabolite of dopamine breakdown

Answer 7

DOPAC and HVA - these can be measured in urine to determine dopamine function

Question 8

What are the main dopaminergic pathways

Answer 8

• A9 pathway
• A10 pathway

Question 9

Describe the A9 pathway

Answer 9

it originates in the substantia nigra to the caudate putamen
it is important in facilitation of voluntary movement
Damage to this pathway results in reduced movement coordination

Question 10

Describe the A10 pathway

Answer 10

neurons from the ventral tegmental area project to two regions of the brain via 2 pathways
- the mesolimbic pathway
(VTA to nucleus accumbens)
- the mesocortical pathway (VTA to cerebral cortex)

Question 11

What is the tuberohypophyseal pathway and how does dopamine affect it

Answer 11

controls prolactin secretion by the pituitary gland and dopamine inhibits its release

Question 12

What is Haloperidol and its role in locomotor activity

Answer 12

it is a dopamine antagonist

it blocks dopamine D2 receptors which suppresses spontaneous locomotor behaviour (exploratory behaviour)
high doses can result in sedation

Question 13

What is Apomorphine and its role in locomotor activity

Answer 13

it is a dopamine agonist
it increases locomotor activity (exploratory behaviour)

Question 14

What are the effects of cocaine on dopamine

Answer 14

it blocks the dopamine transporter which indirectly increases levels of dopamine in the synaptic cleft

Question 15

What is the effect of amphetamine on dopamine

Answer 15

causes release of dopamine from vesicles which increases the level of dopamine in the synaptic cleft - leads to rewarding effects

Question 16

Which pathway is a common reward pathway for drugs of abuse

Answer 16

A10 pathway

Question 17

Describe the effects of morphine on the mesolimbic pathway and what happens when it’s blocked

Answer 17

• morphine acts on the opioid receptors on the VTA and increases dopaminergic cell firing in the VTA and dopamine release on the nucleus accumbens
• the rewarding effects of morphine are due to changes in dopaminergic transmission
• Blockade of the mu receptors in the VTA decreases dopamine release = no reward feeling

Question 18

Name 3 drugs of abuse that act on the mesolimbic dopamine system

Answer 18

• alcohol
• morphine
• cocaine

Question 19

What does modafinil do

Answer 19

inhibits the reuptake of dopamine by binding to reuptake pump