catecholamines

Question 1

are catecholamines hormones or NTs?

Answer 1

both.

Question 2

what type of transmitters are catecholamines?

Answer 2

amine

Question 3

what are amine transmitters synthesised from?

Answer 3

AAs

Question 4

what are the 3 types of catecholamines?

Answer 4

1. dopamine.
2. noradrenaline.
3. adrenaline.

Question 5

which two things react when the cheese effect occurs?

Answer 5

MAOI and tyramine.

Question 6

symptoms of cheese effect:

Answer 6

headache,
high bp,
heart pounding and palpitations.

Question 7

what are some possible complications from the cheese effect?

Answer 7

subarachnoid haemorrhage,
hemiplagia,
intracranial haemorrhage,
cardiac arrhythmias,
cardiac failure,
pulmonary edema,
death.

Question 8

catecholamine transmitters are synthesised from what?

Answer 8

tyrosine.

Question 9

what is tyrosine synthesised from?

Answer 9

Phenylalanine - AA

Question 10

conversion of phenylalanine to tyrosine is catalysed by which enzyme?

Answer 10

phenylalanine hydroxylase.

Question 11

so what is the equation for the conversion of phenylalanine to tyrosine?

Answer 11

phenylalanine + hydroxyl group —–> tyrosine.

Question 12

why are catecholamines called so?

Answer 12

as they contain a catechol group nucleus and an amine group.

Question 13

how is dopamine synthesised? (2 parts)

Answer 13

1. tyrosine + hydroxyl group ——tyrosine hydroxylase——> dopa.
2. dopa - carboxyl group ——dopa decarboxylase—–> dopamine

Question 14

which 2 locations are dopaminergic nuclei found?

Answer 14

1. substantia nigra
2. ventral tegmental area of the midbrain.

Question 15

dopaminergic neurons in the substantia nigra give way to which pathway?

Answer 15

nigrostriatal pathway.

Question 16

Dopamine neurons in VTA give rise to which pathway?

Answer 16

mesocorticolimbic pathway

Question 17

what is the nigrostriatal pathway important for?

Answer 17

motor control.

Question 18

what is the mesocorticolmibic pathway involved in?

Answer 18

reward, reinforcement and appetitive behaviour.

Question 19

which enzyme is rate-limiting in catecholamine synthesis?

Answer 19

tyrosine hydroxylase.

Question 20

what upregulates TH expression?

Answer 20

chronic environmental stress and drugs such as caffeine, nicotine and morphine.

Question 21

what down-regulates the expression of TH?

Answer 21

antidepressants.

Question 22

how can dopamine be inactivated/terminated?

Answer 22

1. by being taken up into the terminal by dopamine uptake transporter (DAT).
2. by being degraded by enzyme MAO.
3. by being catabolised by enzyme COMT.

Question 23

which enzyme metabolises all catecholamines and 5HT?

Answer 23

MAO - both intra and extracellular.

Question 24

what are the 2 isoforms of MAO? and where are they expressed?

Answer 24

MAOA = expressed in dop and noradr neurons.
MAOB = expressed in 5HT neurons, with their axons containing MAOA.

Question 25

What is the affinity of MAO isoforms in relation to dopamine?

Answer 25

MAO A and B have the same affinity to dopamine

Question 26

which isoform is more efficacious to NA and 5HT?

Answer 26

MAO A is more efficacious to noradrenaline and serotonin than B.

Question 27

which disease can be used to treat Parkinson’s?

Answer 27

MAOI.

Question 28

what do COMT receptors do?

Answer 28

COMT inhibitors increase levels of DA and NA in synapses and prolong receptor activation.

Question 29

do DA receptors have inhibitory or excitatory effects?

Answer 29

both.

Question 30

how many types of dopamine receptors are there? what are they called?

Answer 30

5

D1 - D5

Question 31

which 2 categories do dopamine receptors usually belong to?

Answer 31

D1-like receptors,
D2-like receptors.

Question 32

which DA receptors are D1-like and what do they do?

Answer 32

D1 and D5 - they stimulate the activity of adenyl cyclase - they’re excitatory.

Question 33

which DA receptors are D2-like and what do they do?

Answer 33

D2, D3 and D4 - they inhibit activity of adenyl cyclase - inhibitory