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Drugs in Pharmacology > 82 - Drugs in ANS Cholinergic drugs > Flashcards

82 - Drugs in ANS Cholinergic drugs Flashcards

1
Q

Cholinergic drugs act on
A. Skeletal muscles nicotinic receptors

B. Parasympathetic postganglionic muscarinic receptors on skeletal muscles

C. Parasympathetic preganglionic nicotinic receptors

D. Sympathetic postganglionic adrenoreceptors

E. Sympathetic preganglionic nicotinic receptors

A

All except D

All autonomic preganglionic neurons release acetylcholine onto cholinergic nicotinic receptors (ionotropic, ion channels)
> C and E are correct

Cholinergic receptors: acetylcholine-releasing fibers

○ Nicotinic receptor: Ganglionic(Neuronal type), Muscle type (ionotropic receptors > faster action)

Muscarinic receptor: M1- M5 (Modd excitatory; Meven inhibitory) (metabotropic receptors. >slower action)

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2
Q

How can cholinergic receptors be classified?

State the nature of the 2 types of receptors and their actions.

A

Nicotinic receptors

  • ligand- gated ion channels
  • on muscles, ganglion, CNS
  • 4 transmembrane domains

Muscarinic receptors

  • G-protein coupled receptors
  • Odd: Ionositol phosphate (IP3 as 2nd messenger)
  • Even: inhibition of AC
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3
Q

Name the e muscarinic agonists.

A
  1. Acetylcholine
  2. Bethanechol
  3. Carbachol
  4. Methacholine
  5. Pilocarpine
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4
Q

Bethanechol can be used for?

A

Bladder and GI hypotonia

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5
Q

What is the clinical use of pilocarpine?

A

Pilocarpine contracts the iris circular muscle to improve aqueous humour outflow via the Canal of Schlemm by expanding the filtration angle.

This can solve the problem of increased eye pressure in glaucoma patients.

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6
Q

Which G-protein coupled receptors do M1, M2 and M3 receptors activate?

A

M1: Gq protein
M2: Gi protein
M3: Gq protein

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7
Q

What effects are produced when M1, M2 and M3 receptors bind to their respective receptors?

A

M1: CNS excitation, Gastric secretion

M2: Presynaptic inhibition of the heart > slow down the heart

M3: Smooth muscle contraction;
endothelium induced vasodilation;
gastric secretion (parietal gland)
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8
Q

The main function of muscarinic antagonists is?

A

Relaxation

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9
Q

Which muscarinic antagonist is most potent with pA2 9.0?

A

Atropine

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10
Q

Which drug is used for dilating pupil (mydriasis) to see the retina for eye examination?

What is the pharmacological class of this drug?

A

Tropicamide

Muscarinic antagonist to paralysis accommodation

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11
Q

What is the use of tiotropium (in tea) ?

A

Suppresses reflex bronchoconstriction, given by aerosol to restrict its action to the lung

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12
Q

What is muscarinic antagonist used to reduce acid secretion and cure PUD (peptic ulcer disease)?

What kind of muscarinic receptor it is selective to?

A

Pirenzepine

M1 selective receptors

(scold people with 1 finger, angry thus stomachache)

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13
Q

What are the 4 uses of Hyoscine/ Hyoscine N-butyl bromide?

A
  1. Hi! ensure clean airway by reducing secretion and reflex bronchoconstriction (M3)
  2. ai… Slowing of heart rate > prevent it (M2)
  3. 海 motion sickness (M1)
  4. Treat GI hypermotility (brothers > always motile)
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14
Q

Name the 2 most common nicotinic agonist.

A
  1. Acetylcholine

2. Nicotine (more potent)

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15
Q

Name the 2 ganglionic blockers. What are their clinical uses respectively?

A

Trimetaphan
- competitive receptor antagonist for nicotinic Na+ channel

  • Short-term lowering BP (like in the movie avatar)

Hexamethonium

  • Na+ channel blocker
  • antihypertensive (elderly like 韓瑪莉)
  • no longer in clinical use (retired)

different!
trimetaphan competes for the receptor
while Hexamethonium blocks the entire channel

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16
Q

Other than ganglionic blockers, inhibitors of Ach release can also be used.
Name one inhibitor of Ach and explain its MOA.

A

Botulinum toxin

  • degrade SNAP25 ( a component of SNARE) > inhibit exocytosis od Ach
  • cause paralysis of muscles (respiratory muscles)
17
Q

Antitoxin of Botulinum toxin is effective if it is given before appearance of symptoms.

List the 7 uses of Botulinum toxin.

A
  1. Locally for upper motor neuron syndrome
  2. Focal hyperhidrosis - excessive sweating
    (always say high, high doe sweat)
  3. Chronic migraine
  4. Blepharospasm (bless 法老眼zarm zarm)
  5. Bruxism (磨牙磨到牙刷也不用）
  6. Strabismus (heterotropia, cross-eye)
  7. Botox (reduce skin wrinkles)
18
Q

What are the 2 types of acetylcholinesterase?

A

Acetylcholinesterase (AChE): highly selective for Ach, bound to postsynaptic membrane

Butyrylcholinesterase (BChE):widely distributed, also for ester-containing drugs (procaine, suxamethonium)

19
Q

What is the action of Edrophonium on AChE?

A

Edrophonium is an anticholinesterase. It binds to the anionic part of AChE with ionic bond so that ACh canot bind to it.

It is readily reversible and thus short inhibition only.

20
Q

What is the action of Neostigmine on AChE?

A

Neostigmine is an anticholinesterase. It binds to the anionic part + esteralic site of AChE so that Ach cannot bind to it, NH2 group is gradually removed thus there is a longer blocking effect.

Carbamate ester is slowly hydrolysed

> moderate inhibition on AChE

Same as Physostigmine

21
Q

What is the use of Neostigmine?

A

Test for myasthenic gravis;

Rescue for non-depolarizing neuromuscular block produced by tubocurarine (used in surgeries to relax muscles)

22
Q

What is a long-duration anticholinesterase? Why can it achieve a irreversible inhibition on acetylcholinesterase?

A

Dyflos.

Phosphate ester is very stable.

23
Q

What is the major use of anticholinesterases clinically?

A

For diagnosis and treatment of myasthenia gravis.

  • a disease of muscle weakness and fatigue due to reduced number of nAChR at skeletal neuromuscular junctions (NMJ)
  • diagnosis: short-acting edrophonium produces transient improvement on muscle strength
  • treatment: medium-duration neostigmine for longer duration of action
24
Q

Long-acting anticholinesterases are used as? Examples?

A

Insecticide and nerve gases.

Dyflos, Sarin, Ecothiopate (all are organophosphate)

  • severe poisoning may occur from exposure to these agents
  • effects are due to excessive action of ACh at both muscarinic and nicotinic synapses…
25
Q

What are the symptoms for anticholinesterase poisoning in muscarinic receptors?

A. Pupil constriction (miosis)
B. Bronchoconstriction
C. Diarrhea
D. Tachycardia
E. Less glandular excretion
A

All except D and E

D: should be bradycardia (slow heart rate)

E: should be excessive glandular excretion

26
Q

What are the symptoms for anticholinesterase poisoning in nicotinic receptors? (both sympathetic and parasympathetic)

A
  • increase in blood pressure (hypertension)
    by stimulation of sympathetic ganglia,
    then a decrease in blood pressure caused by depolarizing block at the ganglia
  • Skeletal muscle twitch (fasciculation), then paralysis caused by depolarising block at neuromuscular junction

*If untreated, overall effects on the cardiovascular system,
secretion and constriction of airways, and paralysis of
respiratory muscles would lead to death.

27
Q

What can be used to treat anticholinesterase poisoning? (2 drugs)

A
  1. Atropine (not always work as it cannot help if its a nicotinic effect that causes a depolarization block)
  2. Oxime
    e. g. Pralidoxime, Obidoxime
    - reactivate AChE before structural ‘ageing’ occurs by removing the phosphate group from AChE
  • will not cross BBB so little action against central respiratory depression
28
Q

Organophosphate ageing is a chemical stabilization of ______ bond to AChE occurs over time.

_______ prevents ageing can cause regeneration of AChE.

A

Phosphate;

Pralidoxime

Drugs in Pharmacology (5 decks)

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