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Pharmacology > Drugs acting on the sympathetic nervous system (L11) > Flashcards

Drugs acting on the sympathetic nervous system (L11) Flashcards

1
Q

where does NA act as a neurotransmitter?

A

sympathetic nervous system only

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2
Q

what is the sympathetic nervous system?

A

fight or flight response

  • short preganglionic fibre
  • long postganglionic fibre
  • prepanglionic ACh
  • postganglioic NA
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3
Q

NA pharmacology

A
  • precursor is AA tyrosine
  • its transported into neurone by an AA transporter
  • synthesis of NA
  • NA kept in vesicles for protection against cytosolic enzymes
  • NA taken back up by NA transporter and is then broken down by monoamine oxidase or recycled
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4
Q

3 enzymes involved in the synthesis of NA

A

tyrosine hydroxylase
DOPA decarboxylase
DA beta-hydroxylase

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5
Q

the 2 classes of NA receptors

A

alpha

beta

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6
Q

alpha noradrenergic receptors

A

alpha1,2
located in effector tissues/targets of the sympathetic system
GPCP
slow response - seconds

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7
Q

beta noradrenergic receptors

A

beta1,2,3
located in effector tissues/targets of the sympathetic system
GPCP
slow response - seconds

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8
Q

what are sympathetic effects on the body

A
  • pupils dilate
  • lens of eye adjusts for far vision
  • airways in lungs dilate
  • HR increases
  • blood vessels to limb muscles dilate
  • blood vessels to visceral organs and skin constrict
  • brain activity general alertness
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9
Q

what sympathetic effects do alpha1 receptors mediate?

A
  • pupils dilate
  • blood vessels to visceral organs and skin constrict
  • brain activity and general alterness
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10
Q

what sympathetic effects do alpha2 receptors mediate?

A
  • they are presynaptic receptors
  • they turn off further release - negative feedback
  • inhibits neurotransmitter release - both NA and ACh
autoreceptor = own type of neurone 
heteroreceptor = different neurone
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11
Q

what sympathetic effects do beta1 receptors mediate?

A

HR increases

force of contraction increases

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12
Q

what sympathetic effects do beta2 receptors mediate?

A
  • lens of eye adjusts for far vision
  • airways in lung dilate
  • blood vessels to limb muscle dilate
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13
Q

what sympathetic effects do beta3 receptors mediate?

A

increases lipolysis - breakdown of triglycerides to fatty acids

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14
Q

noradrenergic agonists

A 
adrenaline 
clonidine 
dobutamine 
salbutamol 
clenbuterol
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15
Q

adrenaline

A

noradrenergic agonist

agonist against all NA receptors - not selective

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16
Q

clonidine

A

noradrenergic agonist

finish

17
Q

dobutamine

A

noradrenergic agonist

finish

18
Q

salbutamol

A

noradrenergic agonist

finish

19
Q

clenbuterol

A

noradrenergic agonist

finish

20
Q

noradrenergic antagonists

A 
prazosin 
tamsulson 
propranolol
atenolol 
timolol
21
Q

prazosin

A

noradrenergic antagonist

22
Q

tamsulson

A

noradrenergic antagonist

23
Q

propranolol

A

noradrenergic antagonist

24
Q

atenolol

A

noradrenergic antagonist

25
Q

timolol

A

noradrenergic antagonist

26
Q

drugs affecting NA synthesis

A

drugs can give a false substrate

methylDOPA (meDOPA) acts as a false substrate for DOPA decarboxylase

27
Q

drugs affecting NA storage

A

reserpine disrupts storage of NA in synaptic vesicles

overall decrease in NA neurotransmission

28
Q

drugs affecting NA release

A

NA release is subject to auto inhibitory control via presynaptic alpha2 auto receptors

clonidine (alpha2 agonist) causes inhibition of NA release
• overall decrease in NA neurotransmission
• used to treat hypertension

29
Q

drugs affecting NA reuptake

A

NA reuptake can be blocked by NA reuptake inhibitors

this will prolong the action of NA in the synapse

30
Q

drugs affecting NA metabolism

A

NA is metabolised by monoamine oxidase (MAO) and catecholamine transferase (COMT)

by blocking these enzymes the amount of NA available for release is increased

tranylcypromine blocks MAO and allows more NA to be recycled so increases NA neurotransmission

31
Q

cheese reaction

A

tranylcypramine and other MAOIs not only block the metabolism of NA but also block the metabolism of dietary amines (e.g. commonly found in cheese, marmite) and amines found in popular cold remedies

accumulation of dietary amines can have a sympathomimetic effect and result in hypertension

Pharmacology (24 decks)

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