Chemical transmission in the CNS

Question 1

Which receptors does NA act on in the sympathetic NS?

Answer 1

a and b adrenoceptors

Question 2

What is the major NT in the sympathetic NS?

Answer 2

NA

Question 3

What is the major NT in the parasympathetic NS?

Answer 3

Ach

Question 4

Which receptors does Ach act on in the parasympathetic NS?

Answer 4

Muscarinic receptors

Question 5

Which receptors does Ach act on in the somatic NS?

Answer 5

Nicotinic receptors

Question 6

What is the major NT in the somatic NS?

Answer 6

Ach

Question 7

Briefly describe the requirements for chemical neurotransmission?

Answer 7

Synthesis/storage of NTs Release of NTs Inactivation of NTs Receptors for NTs

Question 8

What is required for synthesis and storage of NTs?

Answer 8

Vesicles

Question 9

What is required for release of NTs?

Answer 9

Na and K channels Ca influx

Question 10

What are the two broad mechanisms of NT inactivation?

Answer 10

Reuptake Degradation

Question 11

What are the two major receptor types found at synapses?

Answer 11

Postjunctional and prejunctional

Question 12

What is the trigger for the release of NT from neurons?

Answer 12

Na/K mediated APs > which causes Ca influx > exocytotic release of vesicle

Question 13

How are prejunctional/presynaptic receptors important in transmission?

Answer 13

At high concentrations of NT, NT can bind for reuptake This can act as negative feedback to regulate NT

Question 14

What is the key process for inactivation of NA?

Answer 14

Neuronal uptake

Question 15

What is the secondary mechanisms for inactivation of NA?

Answer 15

Metabolism via MAO Extraneuronal uptake via MAO and COMT

Question 16

Describe the action of cocaine in relation to NA?

Answer 16

Blocks neuronal uptake of NA > increased activation of receptors

Question 17

Describe the action of amphetamine and ephedrine in relation to NA?

Answer 17

Are substrates for carrier and displace NA > reduced reuptake of NA

Question 18

Describe how cocaine differs from amphetamine and ephedrine in its mechanism of action?

Answer 18

Cocaine blocks reuptake receptor Amphetamine and ephedrine act as substrates and displaces NA

Question 19

Which characteristic of cocaine and amphetamines allows them to access their central targets?

Answer 19

Lipid soluble > can cross BBB

Question 20

Which particular functions is NA associated with?

Answer 20

Stimulant effects Mood Appetite Cardiovascular

Question 21

What is the estimate for the number of NTs that act in the CNS?

Answer 21

40

Question 22

Describe the pathway for NA synthesis?

Answer 22

Question 23

What is the precursor for adrenaline synthesis?

Answer 23

NA

Question 24

How do neurons that synthesise adrenaline differ from those that do not?

Answer 24

Presence of enzymes that are able to convert NA to adrenaline

Question 25

Why do some neurons stop at dopamine synthesis, rather than progress on to synthesising NA and adrenaline?

Answer 25

They lack the converting enzymes

Question 26

How do noradrenergic and dopaminergic differ in their distribution in the CNS?

Answer 26

The noradrenergic neurons are more widespread, whereas the dopaminergic neurons are more discrete

Question 27

How does the importance of dopamine differ in the CNS and PNS?

Answer 27

Very important in multiple CNS pathways Less important in PNS, mostly a precursor to NA

Question 28

List some of the pathways in which dopamine is involved in the CNS?

Answer 28

Movement Behaviour Dependence Pituitary function

Question 29

Apart from NA, which other NTs can cocaine block reuptake of?

Answer 29

Dopamine Serotonin

Question 30

Which of the NT actions is linked to the dependence effect of cocaine?

Answer 30

Dopamine

Question 31

Which of the NTs is most strongly linked to the sense of euphoria, wellbeing and appetite effects?

Answer 31

NA Serotonin

Question 32

Why were the NA and serotonin mechanisms the lead for developing antidepressant drugs?

Answer 32

Linked to sense of wellbeing

Question 33

Why were dopaminergic mechanisms avoided when developing antidepressant drugs?

Answer 33

Linked to dependence

Question 34

Why can cocaine be used as a local anaesthetic?

Answer 34

Blocks Na channels

Question 35

Can a synapse be both inhibitory and excitatory in the CNS?

Answer 35

No

Question 36

Can NTs in the CNS be both excitatory and inhibitory?

Answer 36

Yes

Question 37

How can some NTs be both excitatory and inhibitory in the CNS?

Answer 37

Depends on which receptors are present and which part of the brain you are in

Question 38

Which receptor types are present in the CNS?

Answer 38

Ligand-gated ion channels (eg. nicotinic and GABA A) GPCRs (muscarinic, a&b adrenoceptors)

Question 39

What are post-synaptic receptors in the dendritic region important in determining?

Answer 39

AP generation and modulation

Question 40

What are pre-synaptic receptors at the axon terminals important regulating?

Answer 40

NT release

Question 41

What is the predominant role of tyrosine kinase and cytoplamic/nuclear receptors in the CNS?

Answer 41

Neuronal survival, rather than function

Question 42

TAKE HOME MESSAGES

Answer 42

More than one NT usually involved One NT usually involved in many pathways