NORADRENALINE + 5HT

Question 1

What is a catecholamine

Answer 1

• belongs to monoamine groups of transmitters
• core structure of catechol nucleus &nitrogen containing amine
• e.g. noradrenaline - SNS, dopamine

Question 2

Where is tyrosine derived from?

Answer 2

dietry sources

Question 3

How is dopamine produced in the dopaminergic neurone?

Answer 3

Common synthetic pathway
All catecholamines derived from tyrosine
Tyrosine converted to DOPA via tyrosine hydroxylase
DOPA decarboxylase converts DOPA to dopamine
DOPA either a neurotransmitter or an intermediate depending on the role

Question 4

How is adrenaline produced in a noradrenergic neurone?

Answer 4

further from the dopamine producing pathway
dopamine is converted to noradrenaline by dopamine b-hydroxylase
then noradrenaline is converted to adrenaline by phenylethanolamine N-methyltransferase

Question 5

How is the negative feedback loop regulated

Answer 5

by noradrenaline regulating tyrosine hydroxylase

Question 6

What is synthesised in the nucleus

Answer 6

peptide neurotransmitters

Question 7

What are synthesised in nerve terminals

Answer 7

neurotransmitters

Question 8

what occurs in variscosities

Answer 8

• noradrenaline synthesised and released
• there’s a more diffused release of neurotransmitters when released from varicosities

Question 8

What occurs once the neurotransmitters are synthesised?

Answer 8

• Transported into vesicles by VMAT2 (vesicular monoamine transporter) for later release
• prevents spontaneous degradation (from free enzymes)
  -Less enzymes, that degrade the neurotransmitters, inside the vesicle–> therefore protected against degradation
• Allows for regulated release

Question 9

What does reserpine do?

Answer 9

Reserpine can result in extreme behavioural sedation that can be reversed by DOPA
-Prevents dopamine & NA transport into vesicles, resulting in unregulated release & degradation of neurotransmitters

Question 10

What does noradrenaline binding to A2 receptor do?

Answer 10

Noradrenaline binding to pre/post synaptic A2 adrenoceptor (coupled to adenylate cyclase)–> prevents opening of calcium channel–> reduces neurotransmitter release

Question 11

What does binding of noradrenaline do to B2 receptor?

Answer 11

Noradrenaline binding to pre/post synaptic B2 adrenoceptor–> increases release of neurotransmitters

Question 12

What does acetylcholine do when binding to a2 cholinergic receptor?

Answer 12

decrease release

Question 13

what are the pathways of noradrenaline degradation?

Answer 13

Main enzymes are monoamine oxidase (MAO) & catechol-O-methyl transferase (COMT)
MAO predominates in the brain
MAO exists in A & B forms (MAO-A in noradrenergic neurons)
3-methoxy-4-hydroxyphenyglycol (MHPG) is the main noradrenaline metabolite in the brain