Dopamine

Question 1

Classifications of neurotransmitters

Answer 1

Amines
Amino acids
Peptides
Purines

Question 2

Noradrenaline

Answer 2

Controls mood
Controls reward system
Arousal
Blood pressure

Question 3

Where is Noradrenaline stored

Answer 3

locus cocruleus

Question 4

Synthesis pathway of noradrenaline

Answer 4

Tyrosine—->L-DOPA—–>dopamine—–>noradrenaline

Question 5

Tyrosine hydroxylase

Answer 5

Enzyme that converts tyrosine into L-DOPA and is the limiting factor of producing noradrenaline

Question 6

Negative feedback in noradrenaline(end feedback inhibition)

Answer 6

When noradrenaline concentration is high tyrosine hyroxylase is reduced

Question 7

Noradrenaline synapse

Answer 7

Dopamine is taken to synaptic vesicle
Then converted to NA
NA is released from the presynaptic nerve terminal into synaptic cleft
Post synaptic receptors bind with NA
There is also re-uptake of NA back to the pre-synapse

Question 8

NA receptors

Answer 8

a1 receptor-Decreases potassium ion conductance
a2 receptor-Decreases calcium ion conductance
B1 RECEPTORS- Decreases potassium ion conductance
B2 receptors- No pathway

Question 9

What happens when you have a high concentration of dopamine

Answer 9

Can cause schizophrenia

Question 10

3 dopaminergic pathways

Answer 10

Nigrostriatal system(dies in parkinsons disease)
mesolimbic pathway(involved in reward)
Tubero-hypophyseal system(Projects to places that secrete hormones)

Question 11

DA has three functional consequences in the brain:

Answer 11

motor control (A9, nigrostriatal system, 75%).

–behavioural effects (A10, mesolimbic and mesocortical systems to accumbens, amygdala and cortex).

–endocrine control (A12, tubero-hypophyseal system arcuate nucleus of hypothalamus to medial eminence and pituitary gland).

Question 12

Nigro-striatal system

Answer 12

Motor control, motor planning
Loss of dopamine results in akinesia(Lack of voluntary movement)
Unilateral 6-OH dopamine is a toxin affecting dopamine
Toxin placed in one side of the brain and cause turning

Question 13

Mesolimbic/Mesocortical pathways

Answer 13

Motivation, behavioural reward, cognition.
Rewarding properties blocked by dopamine antagonists.
Large doses give rise to stereotyped repetitive inappropriate behaviour patterns such as licking rearing, gnawing

Question 14

tubero-hypophseal system

Answer 14

controls release of hormones
dopamine increases release of growth hormone
inhibits prolactin release

Question 15

Dopamine at other sites

Answer 15

Dopamine can cause nausea and vomiting via chemo receptors

Can cause vasodilation

Question 16

dopamine hypothesis of schizophrenia

Answer 16

schizophrenia unerlined by dopamine hyperactivity

inc. in dopaminergic transmission results in inc. shciz symptoms

Question 17

mesolimbic reward pathway

Answer 17

input to nucleus accumbens by ventraltegmental area & prefrontal cortext, increased dopamine release

Question 18

ampetamine mechanism

Answer 18

blocks DAT transported, blocking dopamine reuptake

• causes dopamine release from displacement(releases dopamine from the presynaptic terminal)

Question 19

signal termination

Answer 19

synaptic reuptake by DAT (transporter)

enzymatic degradation by monoamine oxidase & catechol-o-methyltransferase

Question 20

dopamine receptors

Answer 20

All G protein receptors 2 families
Causes both inhibitory of excitatory actions to cAMP
- D1 -> linked to Gs-> increased adenylate cyclase -> increased cAMP ->(excitatory), D1,D5, postsynaptic transmission , low affinity, for dopamine,

• D2, 3, 4 -> linked Gi, -> decreased -> adenylate cyclase -> cAMP -> (inhibiton), high affinity for dopamine, postsynaptic transmission, presynaptic, heteroreceptor + autoreceptor

Question 21

presynaptic autoreceptor function

Answer 21

D2 activation -> cAMP -> decreased phosphorylation of voltage gated calcium channels -> reduces influx - no exocytosis

Question 22

tissue distribution

Answer 22

D1 & D2 -> most abundant

• found in all fields
• D3 & D4 -> limbic system
• D5 -> hippocampus, hypothalamus, thalamus

Question 23

targets for schizophrenia

Answer 23

schizophrenial

• adhd
• addiction
• endocrine function
• movement disorders