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[Ther 201] 2nd Exam Transes > Cholinergic Receptors and Agents Acting at the Neuromuscular Junction (Jose Paciano Reyes, MD) > Flashcards

Cholinergic Receptors and Agents Acting at the Neuromuscular Junction (Jose Paciano Reyes, MD) Flashcards

1
Q

T/F: Choline entering a neuron via carrier-mediated transport is a rate-limiting step.

A

True

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2
Q

Acetylcholine is released into the neuromuscular junction through what mechanism?

A

Ca2+-mediated exocytosis

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3
Q

What is the rate of degradation of Ach in fast cholinergic synapses?

A

Less than or equal to 1 ms

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4
Q

T/F: Transmission mediated by nicotinic receptors is slower compared to muscarinic receptors.

A

False

It’s the other way around!

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5
Q

(1) is an antagonist to the nicotinic receptor, while (2) is an antagonist to the muscarinic receptor.

A

(1) Curare

(2) atropine

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6
Q

Where are nicotinic Ach receptors located?

A

Ganglia (blocked by hexamethonium)
CNS
NMJ (blocked by tubocurarine)

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7
Q

Where are muscarinic Ach receptors located?

A

M1 - gastric parietal cells
M2 - cardiac & smooth muscle cells
M3 - exocrine glands and smooth muscles

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8
Q

T/F: Nicotinic cholinergic receptors mediate fast EPSPs.

A

True

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9
Q

What are the two types of nicotinic Ach receptor?

A

Neuromuscular and ganglional (8 subtypes of alpha and 4 subtypes of beta)

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10
Q

Enumerate the agonists of the neuromuscular nicotinic Ach receptor

A

Ach
Carbamylcholine (Cch)
Suxamethonium
Decamethonium

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11
Q

Enumerate the agonists of the ganglional nicotinic Ach receptor

A 
Ach
Carbamylcholine (Cch)
Nicotine
Lobeline
Cystisine
Epibatidine
DMPP
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12
Q

Enumerate the antagonists of the neuromuscular nicotinic Ach receptor

A 
Tubocurarine
Pancuronium
Atacurium
Vecuronium
alpha-bungarotoxin
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13
Q

Enumerate the antagonists of the ganglional nicotinic Ach receptor

A

Trimetaphan
Mecamyline
Hexamethonium

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14
Q

Describe the action of alpha-bungarotoxin

A

It blocks postsynaptic nicotinic receptors

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15
Q

Describe the action of beta-bungarotoxin

A

It blocks the presynaptic release of neurotransmitters (similar to botox)

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16
Q

Which cytoplasmic loop in the muscarinic Ach receptor is linked to the G protein?

A

3rd

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17
Q

T/F: Organophosphates are medium-acting, carbamates are long-acting and edrophoniums are very short-acting drug

A

False

Organophosphate - long-acting
Carbamates - medium-acting

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18
Q

Enumerate the types of indirect-acting cholinomimetic drugs

A

Edrophonium
Carbamates
Organophosphates

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19
Q

Enumerate the types of direct-acting muscarinic cholinomimetic drugs

A

Choline esters

Alkaloids

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20
Q

T/F: Choline esters are relatively insoluble in lipids and contain a quaternary ammonium group.

A

True

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21
Q

What are the only choline esters given orally

A

Betanechol and methacholine

This is due to the presence of a beta-methyl group (reduces potency at nicotinic receptor).

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22
Q

What are examples of choline esters?

A

Acetylcholine
Methacholine
Carbachol
Bethanecol (given to patients w/ incontinence)

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23
Q

What are examples of alkaloids?

A

Pilocarpine
Nicotine
Lobeline

These are tertiary amines of plant origin.

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24
Q

T/F: Muscarine, a quaternary amine, is less completely absorbed from the GI tract.

A

True

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25
Q

Alkaloids are chiefly excreted in the (1), enhanced with (2) of the urine.

A

(1) kidney

(2) acidification

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26
Q

What is the duration of action of Ach?

A

5 - 30 seconds

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27
Q

What are the spectra of action of the different cholinomimetic drugs?

A 
Ach - both
Bethanecol - M
Carbachol - B
Pilocarpine - N
Nicotine - N
Varenicline - N
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28
Q

What drug is used for glaucoma as eye drops and has a duration of action of 30 mins to 2 hours?

A

Pilocarpine

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29
Q

What is the duration of action of nicotine?

A

1 - 6 hours

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30
Q

T/F: Varenicline is a partila agonist with a duration of 12 - 24 hours

A

True

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31
Q

What is given to patients to reduce longing for nicotine?

A

Varenicline

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32
Q

What mediates the dilation of arteries and veins?

A

EDRF

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33
Q

What drug blocks the overdose of cholinomimetic drugs that normally leads to diarrhoea?

A

Loperamide

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34
Q

Brain has more (1) receptors, while the spinal cord has more (2) receptors.

A

(1) muscarinic

(2) nicotinic

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35
Q

Describe the effect of nicotine on the CVS, GI and GU.

A

CVS - sympathetic

GI and GU - parasympathetic

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36
Q

Which has a broader substrate specificity - acetylcholinesterase or buterylcholinesterase?

A

Buterylcholinesterase

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37
Q

What drug is used to diagnose myasthenia gravis?

A

Edrophonium (quaternary alcohol)

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38
Q

What is the duration of action of edrophonium?

A

10 minutes (very short-acting)

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39
Q

Enumerate the medium-duration anticholinesterases

A

Neostigmine
Pyridostigmine
Physostigmine

These are carbamic acid esters of alcohol

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40
Q

T/F: Medium-duration anticholinesterases are maintenance drugs for myasthenia gravis and IV forms reverse neuromuscular block.

A

True

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41
Q

For which class of compounds does this phrase apply?

“The longer the bonds stay, the stronger they get.”

A

Organophosphates

42
Q

What class of compounds permanently binds to and deactivates acetylcholinesterase?

A

Organophosphates

43
Q

What are the signs of organophosphate toxicity?

A

Salivation and seizures

44
Q

Organophosphates can cause a severe type of (1)

A

(1) peripheral nerve demyelination

45
Q

Give an example of a cholinesterase regenerator

A

Pralidoxime

46
Q

What is the mechanism of action of pralidoxime?

A

Splits phosphorus-enzyme bond and is most effective before ageing has occurred

47
Q

What is a drug of choice for suicide?

48
Q

What are examples of long-acting cholinesterase inhibitors?

A

Dyfios
Ecothiopate
Parathion

49
Q

For the GI tract, anticholinesterases are used if there is (1)

A

(1) postoperative ileus

50
Q

Cholinesterase inhibitors may be used for the treatment of (1) and overdose of (2)

A

(1) atropine toxicity

(2) tricyclic antidepressants

51
Q

What drugs are used for postoperative ileus?

A

Bethanechol

Neostigmine

52
Q

What drugs are used to treat glaucoma?

A

Carbachol
Pilocarpine
Physostigmine
Echothiaphate

53
Q

What drugs are used to treat symptoms of myasthenia gravis?

A

Neostigmine
Pyridostigmine
Edrophonium

54
Q

What are the symptoms of toxicity of indirect acting agents?

A 
Diarrhea
Urination
Myosis
Bronchoconstriction
Excitation
Lacrimation
Salivation
55
Q

What drugs are used in the treatment of Alzheimer’s disease and dementia?

A

Rivastigmine, galantamine and donepezil

These are centrally-acting cholinesterase inhibitors.

56
Q

T/F: Ganglion stimulants are used as experimental tools and not as clinical treatments.

57
Q

Enumerate the effects of ganglion stimulants

A

Tachycardia
Increased BP
Bronchial, salivary and sweat secretions

58
Q

Give examples of ganglion stimulants

A

Nicotine
Lobeline
Dimethylphenylpiperazinium

59
Q

Give an example of a cholinesterase regenerator

A

Oximes (pralidoxime)

60
Q

Give examples of anti nicotinic classes of drugs

A

Ganglion blockers

Neuromuscular blockers

61
Q

Give examples of anti muscarinic classes of drugs

A

M1-selective (pirenzepine)

Non-selective (atropine)

62
Q

Where is atropine derived from?

A 
Atropa belladona (deadly nightshade)
Datura stramonium (jimsonweed)
63
Q

Where is scopolamine derived from?

A

Hyoscyanius niger (henbane)

64
Q

Atropine and scopolamine are classified as what?

A

Natural alkaloids

65
Q

Give examples of tertiary ammonium cholinergic receptor blockers.

A

Pirenzipine

Tropicamide

66
Q

Give examples of quaternary ammonium cholinergic receptor blockers.

A

Ipratropium

Benztropine

67
Q

T/F: Many antihistamine and antidepressant drugs have similar structures to tertiary ammonium analogs.

68
Q

Enumerate the different tissues that are sensitive to atropine and their level of sensitivity to it.

A

Most sensitive - salivary, bronchial and sweat glands
Intermediate sensitivity - smooth muscles and cardiac tissue
Least sensitive - gastric parietal cells

69
Q

T/F: Atropine is highly selective for muscarinic receptors.

70
Q

What anticholinergic compounds are less specific and may have ganglion-blocking actions?

A

Synthetic anti-muscarinic drugs (e.g. quaternary ammonium’s)

71
Q

What anticholinergic compounds are well absorbed by the gut?

A

Natural alkaloids and tertiary ammonium’s

72
Q

What is the antidote for organophosphate poisoning?

73
Q

What are the symptoms of atropine toxicity?

A 
Blind as a bat (cyclopegia)
Dry as a bone (decreased sweating)
Red as a beet (thermoregulation)
Mad as a hatter (hallucinations)
Hot as hell (fever)
74
Q

Enumerate the different presynaptic cholinergic inhibitors

A 
Hemicholinium
Triethylcholine
Vesamicol
Botulinum toxin
Beta-bungarotoxin
Aminoglycoside antibiotics
75
Q

Enumerate the sites of action of the different presynaptic cholinergic inhibitors

A 
Hemicholinium - reuptake
Triethylcholine - synthesis
Vesamicol - storage
Botulinum - release (ganglion blocker)
Beta-bungarotoxin - release
Aminoglycoside antibiotics - release
76
Q

What is the active ingredient of beta-bungarotoxin?

A

Phospholipase

77
Q

Enumerate the ganglion-blocking drugs that interfere with acetylcholine release

A

Botulinum toxin
Hemicholinum
Mg2+

78
Q

What is given to patients with preeclampsia to prevent seizures and hypertension?

A

Magnesium ion

79
Q

What ganglion-blocking drug causes prolonged depolarisation?

80
Q

Enumerate the ganglion-blocking drugs that interfere with postsynaptic action of acetylcholine

A

Hexamethonium
Trimetaphan
Tubocurarine

81
Q

What are the manifestations of ganglionic blockage?

A 
Loss of CV reflexes
Inhibition of secretions
GI paralysis
Impaired micturition
Hypotension
82
Q

What secondary ammonium compound can enter the CNS and cause sedation, tremor, etc.?

A

Mecamylamine

83
Q

T/F: Hexamethonium has no clinical use.

84
Q

What is trimetaphan used for?

A

Blood pressure lowering

85
Q

Differentiate hexamethonium from decamethonium.

A

Hexamethonium is a ganglionic blocker

Decamethonium is a neuromuscular blocker

86
Q

When are neuromuscular blockers used?

A
  1. Surgery to decrease dose of anaesthetic
  2. Paralysis for intubation
  3. Muscle spasm control
87
Q

What is the mechanism of action of strychnine?

A

Blocks glycine and GABA in spinal cord

88
Q

What are the two classifications under neuromuscular-blocking drugs?

A

Non-depolarizing

Depolarizing

89
Q

What prototype non-depolarising drug prevents access of Ach to its receptors by competitive inhibition?

A

Tubocurarine

90
Q

What is the mechanism of action of the non-depolarising drugs?

A
  1. Act mainly at nicotinic receptor sites

2. May block pre-junctional Na+ channels

91
Q

Non-depolarizing drugs may induce (1) while (2)

A

Motor paralysis

Conscious and aware of pain

92
Q

What is the sequence of motor paralysis by non-depolarising drugs?

A

Extrinsic eye muscles
Small facial muscles
Limbs and pharynx
Respiratory muscles

93
Q

Enumerate the unwanted effects of non-depolarising drugs

A

Tubocurarine - fall in arterial BP and histamine release
Vecuronium - less ganglion block and release of histamine
Gallamine/pancuronium - Tachycardia (M receptor block in heart)

94
Q

Describe depolarizing drugs

A

They are agonists at acetylcholine receptor.

95
Q

What are the two phases in the mechanism of action of depolarising drugs?

A

Phase 1: Depolarizing block (fasciculations)

Phase 2: Desensitizing

96
Q

T/F: Phase 1 block is augmented by cholinesterase inhibitors

97
Q

What are the effects of tetanic stimulation, cholinesterase inhibitors and increased Ach on the block?

A

Tetanic stimulation - relieve
Cholinesterase inhibitors - reverse
Increased Ach - reverse

98
Q

What are the unwanted effects of depolarising drugs?

A 
Bradycardia (prevented by atropine)
Potassium release
Increased intraocular pressure
Prolong paralysis
Malignant hyperthermia
Postoperative muscle pain
99
Q

What do you use to treat patients with malignant hyperthermia?

A

Dantrolene

100
Q

Are Down Syndrome patients at greater risk if they are given succinylcholine?

[Ther 201] 2nd Exam Transes (5 decks)

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