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MTP > Exam 3: Cholinergics Part 1 > Flashcards

Exam 3: Cholinergics Part 1 Flashcards

1
Q

What are the 2 components of acetylcholine?

A

Acetyl ester and quaternary ion

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2
Q

Draw the structure of acetyl choline

A
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3
Q

What structures was Ach get broken down into?

A

Acetic acid and choline

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4
Q

How is ACh biosynthesized?

A

Choline acetyltransferase transfers acetyl group from acetyl CoA to choline

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5
Q

What is the limiting factor of ACh biosynthesis?

A

Choline that is recycled and biosynthesized from Serine

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6
Q

What does ChAT come from?

A

Biosynthesized in the cholinergic neuron

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7
Q

What is the function of acetylcholinesterase (AChE)?

A

Serine hydrolase enzyme that hydrolyzes of ACh forming choline and acetate also inactivating ACh

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8
Q

Describe the acetylcholine metabolism process?

A
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9
Q

What is tranesterification?

A

Transferring the ester group from ACh to the Ser-AChE complex while cleaving the choline.

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10
Q

What makes an ACh enzyme drug successful?

A

Ability to bind to the same receptors as ACh

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11
Q

What type of bonds are developed between receptor and ACh?

A

H from histidine will H-bond with the cholinergic ester. Tertiary nitrogen ionically binds with anionic binding site. Hydroxyl serine attacks the carbonyl carbon.

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12
Q

What is the purpose for fast ACh metabolism?

A

Each synaptic vesicle contains a lot of ACh molecule over receptors. AChE metabolizes it present overstimulation

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13
Q

What are the 2 types of cholinergic receptors?

A
  1. Muscarinic
  2. Nicotinic
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14
Q

How does this molecule match the SAR of Ach?

A

Muscarine: Tertiary ionized nitrogen, 2 carbon bridge, esteratic lone pair

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15
Q

How does this molecule match the SAR of Ach?

A

Nicotine: Tertiary ionizable nitrogen, 2 carbon bridge, 2 nitrogen contains lone pairs

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16
Q

What is the function of this molecule?

A

Pirenzapine: only muscarinic antagonist to block gastric acid secretion at concentrations that did not block the effects of other muscarinic antagonist

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17
Q

Where are M1 receptors located?

A

Neural tissues and various exocrine glands

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18
Q

What is the function of M1 receptors?

A

Involved with memory and learning implicated with Alzheimer’s

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19
Q

Where are M2 receptors located?

A

Postganglionic membranes in the ANS (smooth muscle, heart, exocrine)

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20
Q

What is the function of M2 receptors?

A

Decreases both the rate and contractility of the heart

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21
Q

Where are M3 receptors located?

A

Brain, smooth muscle, and secretory glands

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22
Q

What is the function of M3 receptors?

A

Brain: decrease neurotransmitter release

Smooth muscle and glands: contraction and secretion

23
Q

Where are M4 receptors located?

A

Smooth muscle and secretory glands?

24
Q

What is the function of M4 receptors?

A

Inhibition of calcium channels

25
Q

What molecule was used to identify and study muscarinic subtypes?

A

McN-A343

26
Q

Where are M5 receptors located?

A

Brain and peripheral tissues

27
Q

What is the function of M5 receptors?

A

Whole tissue response in places that match expressed gene products

28
Q

What are SAR requirements for muscarinic agonists?

A
  1. Esteratic site
  2. Anionic site
  3. 2 of the alkyl groups bound to tertiary N must be methyl groups
  4. ACh is not chiral, but receptor has chiral agents
  5. Follows ing’s rule of five
29
Q

Describe the difference between esteratic and anionic sites of muscarinic agonists?

A

E: Acetyl ester oxygen undergos H-bonding

A: Quaternary nitrogen undergos ionic interactions

30
Q

What is Ing’s rule of 5?

A

All potent cholinergic agonists have only 5 atoms between the tertiary nitrogen and terminal hydrogen

31
Q

What can we expect from this ACh conformation?

A

180 degrees, antiperiplanar containing steric bulk therefore is the lowest energy conformation

32
Q

What can we expect from this ACh conformation?

A

60 degrees, synclinal is the observed state in NMR and X-ray solid crystalline form

33
Q

What can we expect from this ACh conformation?

A

137 degrees, anticlinical is the most active conformation is ACh receptors

34
Q

What is the difference between cis and trans ACh?

A

Cis mimics synperiplanar which is eclipsed and sterically unfavored

Trans mimics anticlinal conformation which is favorable

35
Q

What are the classifications of cholinergic and anticholinergic drugs?

A
  1. Muscarinic agonsits
  2. Acetylcholine inhibitors (reversible and irreversible)
  3. Muscarinic antagonists
  4. Nicotinic antagonists
36
Q

Describe the characteristics of this drug?

A
  1. Muscarinic and nicotinic agonist with poor therapeutic agent
  2. Low bioavailability and nonselective action
  3. Quick onset and short duration of action
37
Q

What is the therapeutic use of ACh?

A

Ocular surgery causing complete miosis (constriction) in seconds, instilled in the anterior chamber

38
Q

Describe how ACh properties changes altering A?

A
  1. Increasing length of acetyl ester decreases potency
  2. Aromatic and high MW esters provide cholinergic antagonists
  3. Carbamates increase stability to hydrolysis from AChE
39
Q

Describe how ACh properties changes altering B?

A

Equipotent, Methylation of beta carbon shifts affinity towards muscarinc selectivity

40
Q

Describe how ACh properties changes altering C?

A

Less potent, Methylation of alpha carbon shifts affinity towards nicotinic selectivity

41
Q

Describe how ACh properties changes altering D?

A

Activity decreases as chain length increases

42
Q

Describe how ACh properties changes altering E?

A

3 methyl groups are optimal for activity, removal of methyl reduces activity. Replacing all methyls with ethyls results to antagonism, replacing 1 methyl leads to weak agonist

43
Q

What does this drug accomplish?

A

Methacholine (Amechol, Provocholine)

  1. Slightly more stable than ACh do to beta methy group
  2. More selective to muscarinic
  3. Muscarinic agonist
44
Q

Describe the racemic methacholine?

A
  1. S+ enantiomer is the most active
  2. R- enantiomer is 20 fold less potent
  3. S+ isomer has slow metabolism than ACh
  4. R- isomer is not hydrolyzed by AChE, weak competitive inhibitor of enzyme
45
Q

What does this drug accomplish?

A

Carbachol (Doryl, Milostat)

  1. Potent agonist that is nonselective
  2. Slight indirect activity promoting ACh release and weak AChE activity
  3. Increased hydrolytic stability do to carbamate linkage achieving oral bioavailability
46
Q

What is carbachol used for?

A

Topical for glaucoma and intraocular for miosis in surgery

47
Q

What are the side effects of carbachol?

A

Coreal edema and decreased vision

48
Q

What does this drug accomplish?

A

Bethanechol (Urecholine, Mictone)

  1. Potent muscarinic agonist
  2. Increased hydrolytic stability from b-methyl (gives bulk) and carbamate ester
49
Q

What is the use for bethanechol?

A
  1. Stimulant of GI tract smooth muscle and urinary bladder
  2. For the relief of post-surgical urinary retention and abdominal distension
50
Q

What are the side effects of bethanechol?

A

Low toxicity, no serious, but not caution for asthmatic patients

51
Q

What does this drug accomplish?

A

Pilocarpine (Almocarpine, Pilogel)

  1. Unstable to alkali and bases
52
Q

What is the use for Pilocarpine?

A

Glaucoma and xerostomia

53
Q

What are the side effects of pilocarpine?

A

Copious sweating, salivation, gastric secretion

54
Q

What is the therapeutic use for Cevimeline?

A

Oral capsule for the treatment of xerostamia associated with Sjögren’s syndrome

MTP (15 decks)

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