Cholinergic Agonists & Antagonists

Question 1

To which receptors does ACh bind?

Answer 1

Both nicotinic and muscarinic

Question 2

To which receptors does methacholine bind?

Answer 2

Primarily muscarinic

Question 3

To which receptors does carbachol bind?

Answer 3

Both nicotinic and muscarinic

Question 4

To which receptors does bethanechol bind?

Answer 4

Primarily muscarinic

Question 5

Describe the mechanism of indirectly-acting cholinergic agonists.

Answer 5

They inhibit AChE, so they don’t actually bind the receptor, but they effectively increase the amount of ACh present in the synapse and enhance its effects.

Question 6

Name a tertiary amine muscarinic agonist

Answer 6

Pilocarpine

Question 7

What differentiates pilocarpine from the quaternary amines?

Answer 7

It is able to cross the blood-brain barrier, so it has appreciable CNS effects

Question 8

To which receptors does pilocarpine bind?

Answer 8

Muscarinic only

Question 9

For what is methacholine used?

Answer 9

To test for asthma

Question 10

For what is carbachol used?

Answer 10

As a miotic agent; reduces intraocular pressure

Question 11

For what is bethanechol used?

Answer 11

Stimulates GI motility and bladder control

Question 12

For what is pilocarpine used?

Answer 12

To treat lack of sweat/lacrimation/salivation

Question 13

Three reversible cholinesterase inhibitors discussed in class

Answer 13

Neostigmine
Edrophonium
Physostigmine

Question 14

What does neostigmine do, and what is it used for?

Answer 14

Blocks ACh binding AChE for >1 hour; used to treat myesthenia gravis and reverse the neuromuscular blockade

Question 15

What does edrophonium used for clinically?

Answer 15

Used to test myasthenia gravis progression vs. ACh poisoning; preferential due to its short half-life

Question 16

What does physostigmine do clinically?

Answer 16

Crosses the blood brain barrier and counteracts delirium from anticholinergic activation, such as atropine poisoning

Question 17

What does pralidoxime (2PAM) do?

Answer 17

Helps to treat organophosphate poisoning by restoring function to AChE

Question 18

Muscarinic antagonists

Answer 18

Atropine
Scopalamine
Glycopyrrolate

Question 19

What happens at a high enough concentration of atropine?

Answer 19

Nicotinic cholinergic receptors at the autonomic ganglia will also be blocked

Question 20

Symptoms of atropine poisoning

Answer 20

Dilated pupils
Blurred vision
Dry mouth
Thirst
Dysphagia
Tachycardia
Hypertension
Urinary retention
Respiratory collapse
Hallucinations
Psychosis

Question 21

For what are atropinic agents used?

Answer 21

Bladder problems, nausea/vomiting, overstimulation of the gut

Question 22

What side effects will atropinic agents cause?

Answer 22

Increase in heart rate and mydriasis