Exam II: Cholinergic Agonists Flashcards Preview

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Flashcards in Exam II: Cholinergic Agonists Deck (43):
1

Cycle of ACh (All 6 steps)

1. ACh made from acetyl-CoA and choline
2. ACh stored in neurons ("quanta")
3. Release of ACh when neurons stimulated by an action potential
4. ACh binds to ACh-R
5. AChE breaks down ACh
6. Acetyl-CoA and choline recycled

2

What are the two types of cholinergic receptors?

Muscarinic
Nicotinic

3

Are muscarinic receptors found in the sympathetic or parasympathetic nervous system...or both?

Parasympathetic

4

Where are nicotinic receptors found ( in terms of nervous system...not specific organ )

Ganglionic level of both parasympathetic and sympathetic sides of ANS

5

Do nicotinic receptors have inhibitory capabilities?

No. They only relay the efferent message sent from CNS

6

If a cholinomimetic agent acts to stimulate it is an ______. In contrast, if an cholinomimetic agent acts to inhibit it is an ______.

Direct agonist

Indirect agonist
(by preventing breakdown of ACh)

7

What are the two groups of direct-acting cholinomimetics?

1. Esters of Choline

2. Alkaloids

8

List 4 examples of choline esters

1. ACh
2. Bethanechol
3. Carbachol
4. Methacholine

9

List 4 examples of alkaloids

1. Lobeline
2. Muscarine
3. Nicotine
4. Pilocarpine

10

What are the characteristics of choline esters?

1. Hydrophillic
(they poorly penetrate BBB b/c of their methyl groups pulling electrons and causing a positive charge

2. Hydrolized by AChE

3. Above properties vary on chemical structure

11

All alkaloids are _______ except for _____ which is a ___________.

Tertiary amines
Muscarine
quartenary amine

12

All choline esters are ________.

Quarternary ammoniums

13

What are the characteristics of direct acting alkaloids?

1. Well absorbed after oral administration

2. Lipid soluble --> allows for a larger VD

3. NOT susceptible to AChE

14

What are the three types of AChE inhibitors?

1. Simple alcohols
2. Carbamate Esters
3. Organophosphates

15

Contrast the three AChE inhibitor's binding effects

Simple alcohols = bind weakly and reversibly
--> half life is very short (< 10 min)

Carbamate Esters = bind reversibly but stronger than simple alcohols
--> half life from 30 min to 6 hours

Organophosphates = covalent bonds make it nearly irreversible
--> half-life lasts hundreds of hours

16

Describe the effects cholinomimetics have on the eye and what these effects facilitate.

1. Iris sphincter smooth muscle - contraction, causing miosis (pupil constriction)
2. Ciliary muscle --> contraction (accomodation)

These facilitate aqueous humor flow from the anterior chamber and alter the amount and focus of light reaching the retina

17

What drugs are used to treat glaucoma? Describe the type of these drugs.

Pilocarpine (muscarine agonist)

Physostigmine (carbamate ester...AChE inhibitor)

18

Describe the effects cholinomimetics have on the respiratory system.

Do we use cholinomimetics to treat respiratory conditions?

Cause contraction of bronchiole muscles and stimulate secretion of bronchiole glands (inc. mucous)

We do not use cholinomimetics to tx respiratory conditions

19

Describe the effects cholinomimetics have on the GI system

Increase motility (peristalsis), increase secretion, and relax sphincter muscles

20

What is a GI disorder in which you would use a cholinomimetic to tx

Post-operative ileus --> use neostigmine (AChE inhibitor)

21

Describe the effects of cholinomimetics on the GU system

Detrusor muscle --> contraction
Trigone and sphincter --> relaxation

22

What are cholinomimetics can be used to treat urinary retention?

Bethanecol (Choine ester...direct acting)

Neostigmine (Carbamate ester...indirect acting)

23

What secretory glands do muscarine agonists stimulate?

1. Sweat glands --> diaphoresis
2. Salivary glands
3. Lacrimal glands
4. Nasopharyngeal glands --> snot

24

Muscarinic receptors in the CNS are found to:

1. Induce tremor
2. Cause hypothermia
3. Interfer w/ nocieption (ability to sense stimuli)

25

Nicotinic receptors in the CNS are found to:

1. Induce tremor
2. Stimulate emesis (vomitting)
3. Stimulate respiratory center

26

Indirect cholinomimetics in the CNS can cause:

1. convusions
2. coma
3. respiratory arrest

27

How are cholinomimetics used to threat Alzheimer's Disease?

AChE inhibitors slow progression (do not cure)

28

Name 4 AChE inhibitors used to treat Alzheimer's Dz

1. Tacrine
2. Donepezil
3. Galatamine
4. Rivastigmine

29

What drugs is used to treat smoking cessation? What does it do?

Varenicline

A direct nicotnic agonist that decreases cravings and pleasurable effects of cigarettes

30

Describe how ACh acts at the neuromuscular junction

1. ACh released from presynaptic neurons
2. ACh binds to nicotinic receptors on muscle fiber
3. This results in depolarization of muscle fiber
4. Causes contraction of skeletal muscle

31

Contrast the effects of low, medium, and high doses of indirect cholinomimetics at the neuromuscular junction

LOW DOSE: prolongs effects of ACh, increasing the strength of muscle contraction

MEDIUM DOSE: may cause muscles to fibrillate - muscles not effective

HIGH DOSE: block depolarization causing muscle paralysis

32

Myasthenia Gravis

An autoimmune process of antibodies targeting nicotinic receptors. These antibodies block binding of ACh to receptors

33

What are some symptoms of myasthenia gravis?

Ptosis
Difficulty speaking
Weakness

34

What drugs are used to treat Myasthenia Gravis?

AChE inhibitors

35

What cholinomimetic is used to reverse neuromuscular paralysis (usually following surgery)

Neostigmine (an indirect acting carbamate ester)

36

What do you use to treat an excessive amount of anticholinergic action in the body?

AChE inhibitors (physostigmine) because you want to inc. the amount of ACh at receptor sites

37

Jack eats a mushroom of the genus Inocybe (containing muscarinic alkaloids). What kind of cholinomimetic toxicity does Jack have and what can be done to treat him.

Toxicity of Direct muscarinic agonists

Tx: Atropine

38

What is the fatal dose of nicotine?

40 mg or 1 drop of pure liquid.

2 ciagrettes has this much, but fortunately most gets destroyed by burning

39

Acute nicotine toxicity can cause:

1. CNS stimulation (convusions, resp. arrest, coma)

2. Skeletal muscle depolarization --> leads to blockage and resp. paralysis

3. Hypertension and cardiac arrhythmias

40

How do you treat acute nicotine toxicity?

Supportive until drug is metabolized within a few hours

41

What causes cholineresterase inhibitor toxicity?

Organophosphates and carbamate cholineresterase inhibitors

42

What symptoms are displayed when one has toxicity of cholineresterase inhibitors?

Muscarinic excess

43

How do you treat someone with cholineresterase inhibitor toxicity?

1. Monitor V/S

2. Decontaminate if possible

3. Antidote w/ parenteral atropine or pralidoxime