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Neuropharmacology > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

What are the adenine nucleotide signalling molecules?

A
  • ATP, ADP
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2
Q

What are the adenine nucleoside signalling molecules?

A

Adenosine

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3
Q

What are the stages of purine receptor activation?

A

1) purine synthesis and release 2) extracellular conversions 3) receptor activation

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4
Q

How is adenosine synthesised and released?

A

1) ATP is hydrolysed= AMP 2) AMP is hydrolysed and converted into adenosine via adenosine kinase - ADK can phosphorylate adenosine to from AMP then later ATP

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5
Q

How do purines leave the presynaptic terminal?

A
  • leakage (tissue damage) - exocytosis - adenosine transporter
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6
Q

How are purines packaged into vesicles?

A
  • VNUT (vesicular nucleotide transporter) - requires Na+ concentration gradient generated by ATP
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7
Q

What is the role of nucleotidases in the extracellular space?

A
  • limit ATP signalling - can give rise to other signalling molecules e.g. ADP and adenosine
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8
Q

What is the role of the adenosine transporter?

A
  • equilibrated transporter - operates on concentration gradients - high extracellular adenosine concentration= removed from extracellular space
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9
Q

What receptors does ATP target?

A
  • P2X (ligand gated ion-channels) - P2Y (GPCRs)
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10
Q

What receptor does ADP target?

A

P2Y (GPCRs)

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11
Q

What receptor does adenosine target?

A

P1 (GPCRs)

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12
Q

What are the subtypes of the P2X receptor?

A

P2x1 to 7

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13
Q

What are the subtypes of the P2Y receptor?

A
  • P2Y1, 12, 13 (ADP) - P2Y2, 11 (ATP)
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14
Q

What are the subtypes of the P1 receptor?

A

P1A1, A2A, A2B, A3

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15
Q

What are some effects of antagonists at the P1 receptor?

A
  • cognitive disease - neurodegeneration - asthma/cough - diabetes - diarrhoea
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16
Q

What are some effects of agonists at the P1 receptor?

A
  • sleep disorder - stroke - respirator disorders - cystic fibrosis - cancer - cardiac and kidney ischaemia
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17
Q

What does alpha, beta, methylene-ATP do?

A
  • desensitises P2X receptors - increased concentration decreases number of excitatory junction potentials at NEJ
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18
Q

Is the spontaneous release of ATP inhibited by alpha, beta methylene-ATP?

A

Yes

19
Q

What is the role of varicosities in purine release?

A

The release of ATP means it can be converted to adenosine which inactivates receptors stimulated by ATP= fine parasympathetic control

20
Q

What are areas in the brain where P2X-mediated synaptic transmission has been identified?

A
  • medial habenula - hippocampus The use of nicotinic or glutamate antagonists has little effects in these regions
21
Q

What is the structure of the P2X receptors?

A

Trimeric

22
Q

How does purinergic signalling in pain pathways achieve analgesia?

A
  • P2X antagonists (blocks ATP release from tumour, endothelial and merkel cells) - A1 agonists
23
Q

What do antagonists at the P2X3 receptor treat?

A
  • chronic cough - tissue damage releases ATP activating P2X3 receptors - AF-219 (Gefapixant)= significant decrease in chronic cough
24
Q

What is associated with P2X7 activation?

A

Pain and cell death

25
Q

What prevents P2X7 desensitisation?

A
  • palmitoylation - P2X7 receptor stays in an open state= consistent ion conduction
26
Q

What G protein does P2Y1-11 bind to?

A

G alpha q

27
Q

What G proteins do P2Y-11 bind to?

A
  • G alpha s - G alpha q
28
Q

What G protein does P2Y12-14 bind to?

A

G alpha i/o

29
Q

What is the effect of P2Y12 activation?

A

Platelet aggregation

30
Q

What are antagonists of the P2Y12 receptor used for?

A
  • inhibits process of platelet aggregation leading to artherscleortic plaques - reduces risk of stroke, pulmonary embolus and heart attack - e.g. clopidogrel, ticlopidine
31
Q

What are the functions of the A1 receptor?

A
  • bradycardia - antinociception - reduction of parasympathetic and sympathetic activity - neuronal hyperpolarisation - ischemic preconditioning
32
Q

What are the functions of the A2A receptor?

A
  • inhibition of platelet aggregation - vasodilation - protection against ischemic damage - wound healing
33
Q

What are the functions of the A2B receptor?

A

Relaxation of smooth muscle in vasculature and intestine

34
Q

What are the functions of the A3 receptor?

A
  • enhancement of mediator release from mast cells - preconditioning
35
Q

How does adenosine act as a cardiac ‘retaliatory metabolite’?

A
  • energy supplier e.g. coronary dilation, insulin sensitivity - regulates energy demand e.g. heart rate, adrenergic modulation
36
Q

How is adenosine used to treat supraventricular tachycardia?

A
  • slows heart rate- regulates rhythm
37
Q

What is the role of adenosine during seizure activity?

A

Elevated concentrations of adenosine suppress further seizure activity in the hippocampus= anticonvulsant

38
Q

Why is there certainty that it is adenosine that suppresses seizure activity and not ATP?

A
  • ATP sensor does not detect a signal during seizures - ATP is being converted to adenosine to sustain metabolic demands of the seizure activity
39
Q

What happens when you use an adenosine A1 receptor antagonist?

A

Induces seizure activity in typically non-epileptic tissue e.g. CPT

40
Q

How is adenosine kinase linked with seizure activity?

A
  • increased concentration of ADK reduces extracellular adenosine= facilitates seizure activity - ADK inhibition increases extracellular adenosine= reduces seizure activity e.g. IODO
41
Q

Where is ADK primarily located?

A

Astrocytes

42
Q

What is the role of astrocytes in seizure activity?

A
  • severe epilepsy= astrocyte proliferation - increased ADK presence e.g. via kainic acid
43
Q

When you have both an ADK inhibitor and an A1 antagonist together, would you expect there to be seizure activity?

A

Yes

44
Q

Would a genetic ADK deficiency increase or decrease the risk of seizure activity?

A

Decrease

Neuropharmacology (15 decks)

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