Dopamine Flashcards
1
Q
Source
A
Tyrosine==> l-dopa==> dopamine
2
Q
Rate limiting step
A
tyrosine hydroxylase
3
Q
Breakdown enzymes
A
- monoamine oxidase (MAO) and Catechol-o-methyl transferase (COMT)
- MAO-A selectively metabolises norepinephrine and serotonin
- MAO-B more selectively metabolises dopamine
4
Q
Breakdown product
A
-Homovanillic acid
5
Q
Reuptake
A
- Dopamine transported
- cocaine inhibits this transporter
6
Q
Function
A
-motivation, novelty seeking, reward circuitry, arousal and motor movement in basal ganglia
7
Q
Receptors
A
- 5 types D1-5
- all G protein coupled
- D1-like= D1 and D5- increase adenylate cyclase (stimulatory)
- D1 is post-synaptic and resistant to antagonism
- D5 is more limbic in distribution and has 10x higher dopamine affinity
- D2 like= D2,3&4- decrease adenylate cyclase (inhibitory)
- D4 is in the frontal cortex and clozapine has a high affinity
- D4 selective antagonists do not have antipsychotic efficacy
8
Q
Disorders
A
- low level in Parkinson’s
- high is psychosis especially at mesolimbic area
- may be low in anhedonia and negative symptoms in mesocortical area