catecholamines Flashcards
are catecholamines hormones or NTs?
both.
what type of transmitters are catecholamines?
amine
what are amine transmitters synthesised from?
AAs
what are the 3 types of catecholamines?
- dopamine.
- noradrenaline.
- adrenaline.
which two things react when the cheese effect occurs?
MAOI and tyramine.
symptoms of cheese effect:
headache,
high bp,
heart pounding and palpitations.
what are some possible complications from the cheese effect?
subarachnoid haemorrhage,
hemiplagia,
intracranial haemorrhage,
cardiac arrhythmias,
cardiac failure,
pulmonary edema,
death.
catecholamine transmitters are synthesised from what?
tyrosine.
what is tyrosine synthesised from?
Phenylalanine - AA
conversion of phenylalanine to tyrosine is catalysed by which enzyme?
phenylalanine hydroxylase.
so what is the equation for the conversion of phenylalanine to tyrosine?
phenylalanine + hydroxyl group —–> tyrosine.
why are catecholamines called so?
as they contain a catechol group nucleus and an amine group.
how is dopamine synthesised? (2 parts)
- tyrosine + hydroxyl group ——tyrosine hydroxylase——> dopa.
- dopa - carboxyl group ——dopa decarboxylase—–> dopamine
which 2 locations are dopaminergic nuclei found?
- substantia nigra
- ventral tegmental area of the midbrain.
dopaminergic neurons in the substantia nigra give way to which pathway?
nigrostriatal pathway.
Dopamine neurons in VTA give rise to which pathway?
mesocorticolimbic pathway
what is the nigrostriatal pathway important for?
motor control.
what is the mesocorticolmibic pathway involved in?
reward, reinforcement and appetitive behaviour.
which enzyme is rate-limiting in catecholamine synthesis?
tyrosine hydroxylase.
what upregulates TH expression?
chronic environmental stress and drugs such as caffeine, nicotine and morphine.
what down-regulates the expression of TH?
antidepressants.
how can dopamine be inactivated/terminated?
- by being taken up into the terminal by dopamine uptake transporter (DAT).
- by being degraded by enzyme MAO.
- by being catabolised by enzyme COMT.
which enzyme metabolises all catecholamines and 5HT?
MAO - both intra and extracellular.
what are the 2 isoforms of MAO? and where are they expressed?
MAOA = expressed in dop and noradr neurons.
MAOB = expressed in 5HT neurons, with their axons containing MAOA.
What is the affinity of MAO isoforms in relation to dopamine?
MAO A and B have the same affinity to dopamine
which isoform is more efficacious to NA and 5HT?
MAO A is more efficacious to noradrenaline and serotonin than B.
which disease can be used to treat Parkinson’s?
MAOI.
what do COMT receptors do?
COMT inhibitors increase levels of DA and NA in synapses and prolong receptor activation.
do DA receptors have inhibitory or excitatory effects?
both.
how many types of dopamine receptors are there? what are they called?
5
D1 - D5
which 2 categories do dopamine receptors usually belong to?
D1-like receptors,
D2-like receptors.
which DA receptors are D1-like and what do they do?
D1 and D5 - they stimulate the activity of adenyl cyclase - they’re excitatory.
which DA receptors are D2-like and what do they do?
D2, D3 and D4 - they inhibit activity of adenyl cyclase - inhibitory
