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Pharmacology > Pharm 6 - Cholinomimetics > Flashcards

Pharm 6 - Cholinomimetics Flashcards

1
Q

Describe the synthesis of acetylcholine.

A

Acetylcholine is synthesised from Acetyl CoA and choline via choline acetyltransferase

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2
Q

Why are the receptors described as nicotinic and muscarinic?

A

muscarinic effects can be replicated by muscarine

nicotinic effects can be replicated by nicotine

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3
Q

What can be given to abolish muscarinic effects?

A

Atropine - competitive muscarinic antagonist

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4
Q

State where you would find the different types of muscarinic receptors.

A

M1 - salivary, CNS
M2 - heart
M3 - salivary, bronchial/smooth muscle, eyes, sweat glands

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5
Q

What type of receptor are all muscarinic receptors?

A

G protein coupled receptors

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6
Q

What is the difference in the G-protein receptors of M1/3/5/ and M2/4?

A

m1/3/5/= stimulate PLC which increases IP3 and DAG

M2/4 = inhibitory

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7
Q

Describe the structure of nicotinic receptors.

A

Ligand gated ion channel

5 subunits

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8
Q

What are the two main types of nicotinic receptors?

A

Muscle and Ganglion

Muscle = 2 alpha, beta, delta, epsilon

Ganglion = 2 alpha + 3 beta

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9
Q

Compare the effects of acetylcholine on nicotinic receptors compared to muscarinic receptors.

A

weak effect on nicotinic

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10
Q

What are the 3 effects of muscarinic stimulation on the eye?

A

Contraction of the ciliary muscle (near vision)

Constriction of sphincter pupillae (circular muscle of the eye) constricts pupil

Lacrimation

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11
Q

What are the two effects of constriction of sphincter pupillae?

A

constricts the pupil

increases drainage of intraocular fluid

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12
Q

What is glaucoma?

A

Sustained raised intraocular pressure

can damage optic nerve and retina and cause blindness

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13
Q

Where is aqueous humour produced?

A

ciliary body

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14
Q

Describe the passage of aqueous humour through the eye.

A

passes anteriorly from the ciliary body into the anterior chamber

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15
Q

What drains aqueous humour?

A

Canals of Schlemm

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16
Q

What is the role of aqueous humour?

A

provides oxygen and nutrients to the cornea and iris as they don’t have blood supply as would not be transparent

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17
Q

What happens in angle-closure glaucoma?

A

angle between cornea and iris is narrowed decreasing drainage of humour through canal of Schlemm

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18
Q

What are the effects of giving a muscarinic agonist to people with angle closure glaucoma?

A

causes constriction of sphincter pupillae and opens up the angle to increase drainage of intraocular fluid

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19
Q

Describe the muscarinic effects on the heart.

A

Binding of M2 receptors causes a decrease in cAMP production

triggers a decrease in Ca2+ influx leading to decrease in cardiac output

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20
Q

Describe the muscarinic effects on vasculature.

A

triggers production of NO causing vasodilation and drop in TPR

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21
Q

Summarise the muscarinic effects on the cardiovascular system.

A
  • decrease in heart rate
  • decrease in cardiac output
  • decrease in TPR
  • decrease in blood pressure
22
Q

Describe the muscarinic effects on non-vascular smooth muscle.

A

causes CONTRACTION
lungs - bronchoconstriction
GI - increased motility
bladder - increased bladder emptying

23
Q

Describe the muscarinic effects on exocrine glands.

A

salivation
increased bronchial secretions
increased GI secretions

24
Q

What are two types of cholinomimetic drugs?

A

Directly acting - muscarinic agonists

Indirectly acting - acetylcholinesterase inhibitors

25
Q

What are the two types of muscarinic receptor agonists and give an example of each?

A

Choline Esters - bethanechol

alkaloids - pilocarpine

26
Q

Describe the selectivity of pilocarpine.

A

Non selective muscarinic receptor agonist

stimulates all muscarinic agonists

27
Q

What is pilocarpine used for?

A

Glaucoma (as used locally so cannot stimulate all muscarinic agonists)

28
Q

State some of the side effects of pilocarpine.

A 
Blurred vision
Hypotension
Sweating
Respiratory difficulty
GI disturbance
29
Q

Describe the selectivity of bethanechol.

A

M3 selective agonist

30
Q

What are the effects of bethanechol?

A

assisted bladder emptying

enhanced gastric motility

31
Q

State some side effects of bethanechol.

A 
Blurred vision
Hypotension
Sweating
Respiratory difficulty
GI disturbance
Bradycardia
32
Q

What are the two types of acetylcholinesterases?

A

Reversible

Irreversible

33
Q

Give examples of reversible and irreversible acetylcholinesterases.

A

reversible - physostigmine, neostigmine

irreversible - ecothiopate

34
Q

Where is acetylcholinesterase found?

A

In all cholinergic synapses

Highly selective and rapic

35
Q

Where is butyrylcholinesterase found?

A

found in plasma and most tissues

broad specificity

36
Q

State the effects of low, moderate and high doses of cholinesterase inhibitors.

A

low - enhances muscarinic effects

moderate - further enhances muscarinic effects + stimulates nicotinic receptors

High - depolarising block

37
Q

Describe the mechanism of action of reversible anticholinesterases.

A

Donate carbamyl group which blocks the active site of acetylcholinesterase

carbamyl groups are removed by slow hydrolysis

38
Q

Which synapses does pilocarpine primarily act on?

A

Postganglionic parasympathetic synapses

39
Q

What is physostigmine used to treat?

A

Glaucoma

40
Q

What type of poisoning is physostigmine used to treat?

A

Atropine poisoning

41
Q

How does physostigmine treat atropine poisoning?

A

increases synaptic concentration of acetylcholine so it can outcompete atropine

42
Q

What type of compounds are irreversible anticholinesterases?

A

Organophosphates

43
Q

Describe the mechanism of action irreversible anticholinesterases.

A

react with enzyme active site leaving a large blocking group

blocking group is resistance to hydrolysis

44
Q

What is ecothiopate used to treat?

A

Glaucoma

45
Q

State some side effects of ecothipate.

A 
Blurred vision
Hypotension
Sweating
Respiratory difficulty
GI disturbance
Bradycardia
46
Q

What type of anticholinesterase can cross the BBB?

A

non-polar

47
Q

Describe the effects of low and high doses of anticholinesterase drugs on CNS activity.

A

LOW - CNS excitation

High - unconciousness, resp depression and death

48
Q

State 2 anticholinesterases that are used to treat Alzheimer’s.

A

Donepezil

Tacrine

49
Q

Describe the treatment of organophosphate poisoning.

A

IV atropine

50
Q

What is the acute treatment of organophosphate poisoning?

A

Pralidoxime

Pharmacology (10 decks)

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