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Part 3 – PM3B COPY T > (PM3B) Cholinergic Therapeutics > Flashcards

(PM3B) Cholinergic Therapeutics Flashcards

1
Q

Where does cholinergic transmission occur?

A

In the autonomic nervous system

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2
Q

What is the peripheral nervous system?

A

Output of CNS

Acts independently to regulate body’s internal environment

(1) Autonomic nervous system – ANS
(2) Somatic (motor) nervous system – SNS

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3
Q

What type of nerves control movement?

A

Efferent nerves of somatic (motor) nervous system

Innervate skeletal muscle

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4
Q

What type of nerves respond to external stimuli?

A

Afferent nerves of somatic (motor) nervous system

e.g. nociceptive fibres (pain-sensing)

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5
Q

What systems are in the autonomic nervous system (ANS)?

A

(1) Sympathetic nervous system
– Thoracic-lumbar output
– Synapase at ganglia either side of vertebral column
– Ganglia are distal to innervated tissue

(2) Parasympathetic nervous system
– cranial-sacral output
– Synapse at ganglia close to innervated tissue

(3) Enteric nervous system
– Neurones with cell bodies in intestine wall
– innervates GIT, pancreas, and gall bladder

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6
Q

Name some structures in the sympathetic nervous system.

A
  • eye
  • salivary glands
  • heart
  • lungs
  • adrenal medulla
  • liver
  • GIT
  • bladder
  • genitalia
  • blood vessels
  • sweat glands
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7
Q

Name some structures in the parasympathetic nervous system.

A
  • eye
  • lacrimal gland
  • salivary glands
  • heart
  • lungs
  • upper GIT
  • lower GIT
  • bladder
  • genitalia
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8
Q

What neurones are outside of the CNS in the autonomic nervous system?

A

(1) Preganglionic fibres
- arise from CNS synapse
- releases acetylcholine (ACh)
- cholinergic transmission

(2) Postganglionic nerve
- in ganglia
- terminate at the effector
- most release noradrenaline (NA)
- adrenergic transmission

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9
Q

Which type of neurones in the autonomic nervous system are responsible for cholinergic transmission?

A

Preganglionic fibres

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10
Q

Which type of neurones in the autonomic nervous system are responsible for adrenergic transmission?

A

Postganglionic nerves

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11
Q

How does the CNS act on skeletal muscle?

A

Binding of acetylcholine to nicotinic receptors

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12
Q

How does the CNS act on blood vessels?

A

Release of acetylcholine and binding to nicotinic receptors

Leads to release of noradrenaline

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13
Q

How does the CNS act on sweat glands?

A

Release of acetylcholine and binding to nicotinic receptors

Least to release of further acetylcholine and binding to muscarinic receptors

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14
Q

How does the CNS act on the adrenal medulla?

A

Release of acetylcholine and binding to nicotinic receptors

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15
Q

How does the CNS act on the salivary glands?

A

Release of acetylcholine and binding to nicotinic receptors

Least to release of further acetylcholine and binding to muscarinic receptors

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16
Q

Which nerves release ACh?

A

All postganglionic parasympathetic nerves
- to act on mAChRs

All motor nerves
- to act on nAChRs

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17
Q

Where are M1 receptors located?

A

Ganglia in CNS

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18
Q

Where are M2 receptors located?

A

Cardiac

CNS

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19
Q

Where are M3 receptors located?

A

Glands + smooth muscle + blood vessels

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20
Q

Where are M4 receptors located?

A

CNS

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21
Q

Where are M5 receptors located?

A

CNS

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22
Q

What is the function of M1 receptors?

A

Excitation + secretion

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23
Q

What is the function of M2 receptors?

A

Cardiac + CNS inhibition

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24
Q

What is the function of M3 receptors?

A

Secretion

Contraction

Vasodilatation

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25
What is the function of M4 receptors?
Enhanced movement
26
What is the function of M5 receptors?
Unknown
27
Which G protein does an M1 receptor act on?
G-alpha q
28
Which G protein does an M2 receptor act on?
G-alpha- i/o
29
Which G protein does an M3 receptor act on?
G-alpha q
30
Which G protein does an M4 receptor act on?
G-alpha- i/o
31
Which G protein does an M5 receptor act on?
G-alpha q
32
What is the response following binding of an M1 receptor?
Increased IP3
33
What is the response following binding of an M2 receptor?
Decreased cAMP
34
What is the response following binding of an M3 receptor?
Increased IP3
35
What is the response following binding of an M4 receptor?
Decreased cAMP
36
What is the response following binding of an M5 receptor?
Increased IP3
37
What is the effect of binding to a muscarinic receptor eliciting an effect on a G-alpha q G protein?
Increased IP3
38
What is the effect of binding to a muscarinic receptor eliciting an effect on a G-alpha i/o G protein?
Decreased cAMP
39
Name some agonists of muscarinic receptors.
(1) Acetylcholine (2) Carbachol (3) Oxotremorine (4) Pilocarpine (5) Bethanechol
40
What are some antagonists of an M1 receptor?
(1) Atropine | (2) Pirenzepine
41
What are some antagonists of an M2 receptor?
Atropine
42
What are some antagonists of an M3 receptor?
(1) Atropine | (2) Darifenacin
43
What are some antagonists of an M4 receptor?
Atropine
44
What are some antagonists of an M5 receptor?
Atropine
45
What are some general effects of muscarinic receptor agonists?
(1) Bradycardia/ reduced cardiac output (2) Vasodilation (3) Increased secretion - salivation - lacrimation - sweating (4) Bronchoconstriction + increased bronchial secretion (5) Increased gut motility (6) Reduction of intraocular pressure - a result of pupillary constriction
46
When is an mAChR agonist used in glaucoma?
A mitotic (pilocarpine) used to reduce intraocular pressure Action lasts ~1 day
47
When is an mAChR agonist used in urinary retention?
Bethanechol To relieve urinary retention
48
When is an mAChR agonist used in constipation?
Bethanechol Increase gut motility
49
What is the acronym SLUDGE in regard to mAChRs?
``` S = salivation L = lacrimation U = urination (relaxation of internal sphincter + contraction of detrusor muscles) D = defecation G = gastrointestinal upset E = emesis (vomiting) ```
50
What is emesis?
Vomiting
51
Why is therapeutic use of mAChRs limited?
Causes SLUDGE
52
What are some actions of mAChR antagonists?
(1) Block secretion - salivary - lacrimal - sweating - bronchial (2) Tachycardia (3) Pupillary dilation (4) Inhibition of gut motility (5) Bladder paralysis (6) Smooth muscle relaxation (except gut) (7) Excitatory CNS effects
53
What can blocked secretion, due to use of mAChR antagonists, lead to?
Dry mouth
54
What can pupillary dilation, due to use of mAChR antagonists, lead to?
Increased intraocular pressure
55
What can inhibition of gut motility, due to use of mAChR antagonists, lead to?
Constipation
56
What can paralysis of the bladder, due to use of mAChR antagonists, lead to?
Urinary retention
57
What can the excitatory effects on the CNS, due to use of mAChR antagonists, lead to?
Disorientation Mood swings
58
When are mAChR antagonists used for ophthalmic purposes?
(1) Tropicamide - to dilate pupils (mydriasis) - to aid eye examinations (2) Atropine/ cyclopentolate - to paralyse the eye - to treat inflammation
59
When are mAChR antagonists used for bronchodilation purposes?
(1) Ipratropium - orally inhaled aerosol - short-acting - half-life 2-4 hours - acute asthma (2) Tiotropium - orally inhaled aerosol - half-life ~10 hours - long-acting - COPD
60
When are mAChR antagonists used for reducing intestinal motility?
(1) Atropine/ dicycloverine - smooth muscle relaxant - anti-spasmodic agents - management of IBS - management of diverticular disease (presence of pouches in wall of intestine)
61
When are mAChR antagonists used for treating urinary incontinence?
(1) Tolterodine/ oxybutynin - treatment of OAB (overactive bladder) - extended-release formulation OD Ideally want a selective M3 antagonist such as darifenacin/ solifenacin
62
When are mAChR antagonists used for cardiovascular purposes?
(1) Atropine - bradycardia - after MI
63
When are mAChR antagonists used for nausea and vomiting?
(1) Hyoscine - transdermal patch - orally - treatment of motion sickness - acts on 'vomiting centre' of hind brain medulla
64
When are mAChR antagonists used for Parkinson's disease?
(1) Trihexyphenidyl hydrochloride - treatment of dopamine deficiency - due to overactivity of cholinergic transmission
65
When are mAChR antagonists used for anaesthesia?
(1) Atropine/ hyoscine - inhibition of salivation/ bronchial secretion - cause drowsiness (2) Atropine/ glycopyrronium - during surgery - prevent vagal inhibition of the heart
66
What is the function of nicotinic receptor subtypes?
Excitation
67
Where are nicotinic receptors in muscle located?
Postsynaptic Neuromuscular junction (NMJ)
68
Where are nicotinic receptors in ganglia located?
Postsynaptic ganglia
69
Where are nicotinic receptors in CNS located?
Pre- and post- synaptic
70
What are some agonists of nicotinic receptors located in muscle?
(1) Acetylcholine | (2) Succinylcholine
71
What are some agonists of nicotinic receptors located in ganglia?
(1) Acetylcholine | (2) Nicotine
72
What are some agonists of nicotinic receptors located in the CNS?
(1) Acetylcholine | (2) Nicotine
73
What are some antagonists of nicotinic receptors located in muscle?
(1) Tubocurare | (2) Pancuronium
74
What are some antagonists of nicotinic receptors located in ganglia?
(1) Trimetaphan | (2) Hexamethonium
75
What are some antagonists of nicotinic receptors located in the CNS?
Mecamlylamine
76
Why are most nicotinic acetylcholine ligands therapeutically undesirable?
Lack of selectivity between sympathetic + parasympathetic ganglia
77
What effects do the ganglion-blocking drugs trimetaphan and hexamethonium have?
(1) Cardiovascular - block of sympathetic system - vasodilation causes fall in BP - trimetaphan used to induce hypotension in surgery (2) GIT - block of parasympathetic system - inhibition of motility (3) Genito-urinary system - block of parasympathetic system - impairment of micturition (urination)
78
How do neuromuscular blocking agents work?
(1) Competitive antagonists - widely used as muscle relaxants - adjunct to anaesthesia - e.g. pancuronium, vecuronium, atracurium (2) Agonists which cause a depolarising block of muscle endplate (depolarising blockers) - to cause paralysis during anaesthesia - e.g suxamethonium (succinylcholine)
79
What are the stages of cholinergic transmission?
(1) Acetyl CoA + choline produce ACh in the presence of CAT (2) ACh is packaged into vesicles and released into synaptic cleft (3) Binds to mAChR or nAChR on postsynaptic membrane to elicit a cellular effect
80
What happens to excess ACh in the synaptic cleft?
(1) Broken down into choline + acetate by acetylcholinesterase (2) Endocytosis of choline + acetate
81
Name a drug that prevents vesicle release in cholinergic transmission.
Botulinum toxin
82
Name some therapeutic acetylcholinesterases.
(1) Donepezil (2) Galantamine (3) Rivastigmine
83
What is the function of vesamicol?
Block packaging of ACh into vesicles
84
What is the function of hemicholinium?
Blocks choline reuptake
85
What is the function of botulinum toxin type A?
Blocks vesicle docking/ release Causes dry mouth/ blurred vision Can lead to respiratory paralysis
86
What are some therapeutic applications of botulinum toxin?
(1) Muscle spasm - focal dystonic spasms (writer's cramp) - spasmodic dystonia - pain associated with continual muscle contraction (2) Migraine/ headache - facial muscle contractions causing headaches (3) Excessive secretion - severe underarm sweating - severe salivation - when not managed effectively with topical agents - can be effective for 6-10 months
87
What amino acid binding sites are present in cholinesterase?
(1) Histidine - catalytic (active) site (2) Serine (3) Glutamate - allosteric (anionic) site
88
What are the main classes of anticholinesterase?
(1) Short-acting - e.g. edrophonium (2) Medium-duration - e.g. neostigmine/ pyridostigmine (3) Irreversible - e.g. ecothiopate
89
What is the mechanism of action of neostigmine?
Inhibits cholinesterase Binds to serine of cholinesterase
90
What is myasthenia gravis?
Autoimmune disease Leads to depletion of nAChRs at NMJ Use of neostigmine/ pyridostigmine as they are able to cross BBB
91
What are some therapeutic uses of anticholinesterases?
(1) Myasthenia gravis (2) Dementia (3) Reversal of competitive neuromuscular block after anaesthesia
92
Why are anticholinesterases used for treatment of dementia?
Alzheimer's is associated with loss of cholinergic neurones in basal forebrain Donepezil, rivastigmine + galantamine used to treat mild-moderate AD
93
What anticholinesterases are used for reversal of competitive neuromuscular block after anaesthesia?
(1) Edrophonium - transient action | (2) Neostigmine

Part 3 – PM3B COPY T (33 decks)

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