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Julie Pharm > Cholinergic agonist > Flashcards

Cholinergic agonist Flashcards

1
Q

Cholinomimetics - what are they and the two types

A

agents that activate ACh receptors either directly or indirectly

direct - agonist
indirect - ACh esterase inhibitor

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2
Q

Where is ACh released

A

all preganglionic nerve fibers + all postganglionic parasympathetic nerve fibers

predominant autonomic tone -> parasymp

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3
Q

exceptions of where parasym isn’t involved

A

vasculature - no parasympathetic input

sweat glands -> cholinergic sympathetic fibers

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4
Q

synthesis and release ACh

A

Acetyl CoA + choline = ACh { ChAT = choline acetyl transferase}

  1. acetyl CoA is an intermediate in glucose metabolism
  2. choline is present in all cells
  3. ChAT present in cytosol
  4. newly synthesized ACh -> synaptic vesicles
  5. ACh released from nerve ending by exocytosis degraded by acetylcholinesterase which is present in synaptic cleft
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5
Q

degradation of ACh

A

ACh= choline + acetate [ AChE = acetylcholinesterase]

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6
Q

acetylcholine receptors ( 2)

A

muscarinic and nicotinic

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7
Q

nicotinic - location and type of receptor

A

ligand gated ion channels

  • in muscle, autonomic ganglia, adrenal chromaffin cells and brain
  • neuronal nAChRs -> not in muscle can be distingushed pharmacologically
  • pentamers
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8
Q

muscarinic - type and location

A

gtp- binding protein linked receptors

upon activation alter second messenger pathways

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9
Q

Nicotinic muscle ( tissue and action)

A

NMJ and transient depolarization ( increase Na and K)

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10
Q

Neuronal Nicotinic ( tissue and action_

A

autonomic ganglia -> transient depolarization

adrenal medulla, CNS-> increase internal Ca

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11
Q

Muscarinic ( M2)

tissue and action

A

Cardiac - hyperpolarization : increase K and decrease rate of contraction
CNS ; presynaptic terminals -> decrease cAMP

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12
Q

Muscarinic (M3)

tissue and action

A

smooth muscle -> PI turnover and increase Ca
secretory glands -> increase cAMP

smooth muscle contraction

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13
Q

Muscarinic (M1)

tissue and action

A

autonomic ganglia , CNS PI turnover increase Ca and increase cAMP

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14
Q

Muscarinic (M4)

tissue and action

A

CNS decreases cAMP

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15
Q

Muscarinic (M5)

tissue and action

A

PI turnover; increase Ca and increase cAMP

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16
Q

All muscarinic receptors are selectively blocked by

A

ATROPINE - no receptor subtype agonist exists that is clinically useful

17
Q

Nm and Nn are selectively blocked by

A

curare and mecamylamine respectively

18
Q

Effect of ACh on muscarinic receptors on

  1. vasculature
  2. bronchi
  3. eye iris
  4. ciliary muscle
  5. salivary glands
  6. lacrimal glands
  7. sweat glands
  8. GI tracts
  9. urinary bladder
  10. heart
A
  1. vasculature -> vasodilation, release of EDRF decrease in bp
  2. bronchi -> constriction, increase in mucosal secretions
  3. eye iris- contraction and miosis
  4. ciliary muscle - contraction- lens accommodations for near vision
  5. salivary glands- secretion - thin and watery
  6. lacrimal glands - secretion
  7. sweat glands - diaphoresis
  8. GI tracts - increase tone ( motility) relaxation at sphincters
  9. urinary bladder - contraction of detrusor, relax sphincters
  10. heart - bradycardia and decrease in conductions
19
Q

ACh effect on nicotinic receptors

A

all gang- genral stimulation, predominate tone depends of tissue
adrenal medulla - release of epi
skeletal muscle - contraction/ relaxation

20
Q

vasculature and effect of Ach

A

blood vessels contain no cholinergic input but endothelium with in the vessels have muscarinic

ACh receptors and upon stimulation NO is released -> vasodilation

  • low dose of ACh -> decrease in BP followed by baroreceptor induced tachy
  • if pretreated with atropine ( m antagonist) bp doesnt drop as much
21
Q

ACh and the brain

A

ACH and related choline esters are all permanently charged, quaternary amines and dont penetrate into the CNS

but adrenal medulla is effected -> epi

22
Q

uses of acetylcholine

A

rapidly hydrolyzed by cholinesterases
limited clinical use
- intraocularly to produce miosis after lens extraction
- used during diagnostic coronary angiography where intracoronary injection causes vasodilation

23
Q

methacholine

A

agonist at mAChRs
may be used for diagnosis of bronchial hyperactivity and asthmatic conditions very carefully
- not very susceptible to AChE (+)
no effect at muscarinic receptors

24
Q

Carbachol

A

agonist at all AChRs
used for wide angle glaucome, only when other cholinomimetics are no longer effective

cholinesterase -negligible
mus ++
nic +++

25
Q

Bethanechol

A 
Agonist at GI mAChRs 
used postop after abdominal surgery and postpartum to decrease badder distention 
-promotes salvations 
- cholinersterase - negligible 
mus ++
nic - none

BBB- bethanechol, bowel and bladder

26
Q

Side effects of choline esters

A 
all related to muscarinic stim
Diarrhea 
urination
miosis 
bradycardia 
emesis 
lacrimation
lethargy
salivation 
( decrease in night vision, trouble focusing on distant objects)
27
Q

contraindications for use of choline esters

A
  1. asthma-> may precipitate attack due to muscarinic mediated bronchial contraction
  2. urinary obstruction
  3. acid-peptic disease- may induce gastric acid secretion
28
Q

plant alkaloids (3)

A
  1. pilocarpine
  2. muscarine
  3. nicotine
29
Q

pilocarpine

A

agonist at mAChRs
- miotic agent ( lasts 1 daY)
-wide angle glaucoma
- AChE inhibitor for emergency narrow angle glaucoma
-oral to overcome xerostomia ( decrease salvation)
-side effects - dumbells
chronic use-> decrease in night vision and focusing on distant objects

30
Q

muscarine

A

agonist of mAChRs
muscarine poisoning ; rapidly developing symptoms (30-60 min) revered with atropine
- salvation, lacrimation nausea , vomiting, visual disturbances, bronchospasm, bradycardia and hypotension, shock

Julie Pharm (14 decks)

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