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Pharmacology > Cholinergic Mechanism > Flashcards

Cholinergic Mechanism Flashcards

1
Q

Direct cholinergic responses are mediated by:

  1. Muscarinic receptors at❓
  2. Nicotinic receptors at❓
A
  1. Parasympathetic
    Postjunctional
    Neuroeffector sites
  2. Parasympathetic ganglia
    Sympathetic ganglia
    NMJ of the somatic nervous system
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2
Q

Muscarinic receptors are:

  1. Members of seven transmembrane domain
  2. G-coupled receptors
  3. Functional and structurally unrelated to nicotinic receptors

True or false

A

True

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3
Q

Describe the nicotinic Ach receptor

A
  • Ligand gated ion channel
  • 5 subunits (2a, 1b, 1g, 1d)
  • Receptor opens transmembrane ion channel when Ach bind on extracellular a-subunit sites
  • Muscle, ganglionic and CNS types
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4
Q

Are M1, M3 and M5 receptors are generally excitatory or inhibitory in nature❓

How do they bring about this effect❓

A

M1, M3, M5 receptors are excitatory in nature

⬆️IP3/DAG activity

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5
Q

Are M2 and M4 receptors are generally excitatory or inhibitory in nature❓

How do they bring about this effect❓

A

Inhibitory

⬇️cAMP

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6
Q

Are N1 and N2 receptors are generally excitatory or inhibitory in nature❓

How do they bring about this effect❓

A

Excitatory

⬆️cation conductance

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7
Q

Acetylcholine is an ester of acetic acid and choline

True or false❓
What limits it utility physiologically❓

A

True

  • Lack of selectivity (both M -Ach and N-Ach)
  • Rapid degradation by cholinesterases
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8
Q
  1. What properties do direct acting agonist of Ach receptors have❓
  2. List some examples of choline esters
  3. List selective agonists of muscarinic receptors
  4. Carbacol can activate both receptors. True or false❓
A
  1. Acetyl group in Ach replaced by carbamoyl group

Substitution of methyl group of beta carbon

  1. Bethanecol
    Carbacol
    Methacoline
  2. Bethanecol
    Methacoline
  3. True
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9
Q

At usual therapeutic doses, the effects of carbacol on ACh is dependent on the activation of muscarinic receptors

True or false❓
Why❓

A

True

Greater abundance and accessibility compared to NAch

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10
Q

List the choline non-esters you know

A

Pilocarpine

Muscarine

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11
Q

What do you know about Pilocarpine❓

A
  • Crosses membranes easily
  • Crosses BBB
  • Rapidly absorbed by cornea of the eye
  • Unaffected by cholinesterases
  • Naturally occurring
  • Cholinomimetic alkaloid
  • Tertiary amine
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12
Q

Muscarine is an alkaloid with no therapeutic use, however, it can cause dangerous cholinomimetic stimulation after ingestion of some mushrooms

True or false

A

True

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13
Q

What is the effect of cholinesterase inhibitors❓

A

Prevent degradation of Ach/Prevent ACh binding

⬆️Ach in the system

⬆️Stimulation of muscarinic and nicotinic receptors

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14
Q

AchE can be inhibited by which mechanisms❓

A
  1. Binding to anionic site/Competitive binding

2. Binding to esteratic site (false substrate for cholinesterase)

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15
Q

What are the two major classes of AChE inhibitors❓

List a few examples

A 
Carbamates/Carbamic Acid Esters: 
Physostigmine 
Neostigmine 
Pyridostigmine 
Rivastigmine (good brain penetration)
Organophosphate Esters: 
Echothiophate 
Parathion 
Malathion 
Isoflurophate

*Echothiophate is not lipid soluble

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16
Q

What is the mechanism behind carbamate inhibition of AChE❓

What is the mechanism behind organophosphate inhibition of AChE❓

A
  1. •A carbamylated intermediate is formed (instead of an acetylated one)

•carbamylated enzyme undergoes hydrolysis much more slowly

*Recovery time is in minutes or hours

2. 
Binding to esteratic site 
⬇️
Stable bond btwn phosphate and AChE
⬇️
”Irreversible inhibition”

*Recovery time is in days

17
Q

Do you know any quaternary ammonium compounds closely related to carbamates❓

How do they inhibit AChE❓

A
  1. Edrophonium (monoquaternary)

Ambenonium (bisquaternary)

2.
\+vely charged 
⬇️
Bind to anionic site competitively
⬇️
Displaces ACh from active site without covalent modification
18
Q

What is the duration of action of:

A) Endrophonium
B) Ambenonium

A

A) 5-10minutes

B) 4-8hours

19
Q

List some organ responses to cholinergic agonists

A

1.
Heart:

AV node: ⬇️dromotropy
Atria/Ventricles: ⬇️inotropy
SA node: ⬇️chronotropy

2.
Eye:

Sphincter muscle: C: Miosis
Cilliary muscle: C: Accommodation

  1. Glands:

Lacrimal: ⬆️
Sweat: ⬆️
Salivary: ⬆️

  1. Lungs:
    Bronchial muscle: C
    Bronchial glands: ⬆️ secretion
  2. Urinary bladder:

Detrusor muscle: C
Trigone and sphincter: R

  1. GIT:

Intestines: ⬆️motility
Sphincters: R
Glands: ⬆️

20
Q

1.
List some AChE, CNS inhibitors you know

  1. Are they reversible or irreversible inhibitors❓
A
  1. Tacrine
    Donepazil
    Galantamine
  2. They are reversible
21
Q

Which ACh direct agonist would you use in initiating micturition in acute, non-obstructive urinary retention❓

A

Bethanecol

22
Q

Which ACh direct agonist would you use in producing miosis in the treatment of glaucoma❓

A

Pilocarpine

23
Q

ACh is used in causing miosis during cataract surgery of short duration

True or false

A

True

Carbacol is used for longer durations

24
Q

Which ACh indirect agonist would you use in producing miosis in the treatment of glaucoma❓

A

Physiostigmine

25
Q

Which ACh indirect agonist would you use in producing miosis in the diagnosis and treatment myasthenia gravis❓

A

Endrophonium

Ambenonium

Neostigmine

26
Q

Which ACh indirect agonist would you use to counteract intoxication of anticholinergics❓

A

Physostigmine

27
Q

Which ACh indirect agonist would you use to improve cognitive functions in AD patients❓

A

Tacrine

Galantamine

Rivastigmine

28
Q

Which ACh indirect agonist would you use to treat paralytic ileus or cardiac tacharrythmias❓

A

Edrophonium

29
Q

What are the adverse effects of cholinergic agonists❓

A

Congested conjunctiva
Myopic accommodation
Transient lenticular opacity

Headache
Syncope
Tremors

Nausea 
Vomiting 
Abdominal cramps
Diarrhea 
Salivation

Bradycardia
Hypotension

Bronchospasm

Sweating
Lacrimation
Flushing

Pharmacology (10 decks)

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