Dopamine Flashcards
What is dopamine?
Dopamine is a chemical messenger involved in various pathways throughout the brain.
What functions are aided by dopamine?
Voluntary movement
Emotions and reward
Vomiting.
What are the stages of dopamine synthesis?
Glycine - Alanine - Phenylalanine - Tyrosine - Dihydroxyphenylalanine (DOPA) - Dopamine.
Why can we not give pure dopamine to a patient with Parkinson’s disease?
Dopamine cannot cross the blood brain barrier.
How is dopamine affected within Parkinson’s disease?
Degeneration of dopamine cells in the substantial nigra and dopamine deficiency in the basal ganglia.
What is the typical presentation of Parkinson’s?
Stiff
Slow movements
Postural changes
Tremor
What are the 2 pathways of dopamine metabolism?
Dopamine - Dihydroxyphenylacetic acid - Homovanillic acid.
Dopamine - 3-methoxytryptamine (3MT) - Homovanillic acid.
What enzyme catalyses dopamine to dihydroxyphenylacetic acid?
Monoamine oxidase B (MAO-B)
Which enzyme catalyses dihydroxyphenylacetic acid to homovanillic acid?
Catechol-O-methyltransferase (COMT)
Which enzyme catalyses dopamine to 3MT?
Catechol-O-methyltransferase (COMT)
Which enzyme catalyses 3MT to homovanillic acid?
Monoamine oxidase B (MAO-B)
Give an example of a dopaminergic precursor?
Levodopa - can cross the blood brain barrier.
What are the 2 classes of dopamine agonists?
Ergots and Non-ergots
Give some examples of Ergots?
Bromocriptine
Pergolide
Cabergoline
Give some examples of Non-ergots?
Ropinirole
Rotigotine
Pramipexole
Give some examples of enzyme inhibitors that effect the metabolism of dopamine?
MAO-B inhibitor - Selegiline, Rasagiline, Safinamide.
COMT inhibitor - Entacapone, Tolcapone
These increase the effects of levodopa.
What are some side effects of dopaminergic drugs?
Nausea
Vomiting
Psychosis
Impulsivity and abnormal behaviours - public indecency, binge eating, gambling, shopping addiction.
What is the advantage of Domperidone?
Domperidone is a dopamine antagonist that does not cross the blood brain barrier, therefore it does not worsen PD whilst also improving side effect symptoms.
