Neuromuscular blocking agents

Question 1

How many ACh molecules are needed to open the nicotinic receptors?

Answer 1

2

Question 2

Where are the binding sites for ACh located on the receptor?

Answer 2

on the alpha subunits always

Question 3

how many alpha subunits are on the nicotinic receptor?

Answer 3

2 out of the 5 total subunits

Question 4

What is an important feature of drugs that interact with the nicotinic receptor?

Answer 4

they are large structures that look like they’re made from 2 ACh molecules, this makes sense because there are 2 ACh binding pockets on the receptor that the drug molecule has to bind to

Question 5

what is the only depolarizing agent for nicotinic receptors?

Answer 5

succinylcholine

Question 6

what is succinylcholine’s mechanism of action?

Answer 6

it binds to both of the receptor sites on the channel and then causes it to open. this causes initial muscle spasms, but then the drug stays on the receptor and it stays open (aka the muscle stays depolarized) so the drug is now causing paralysis

Question 7

what is flaccid paralysis?

Answer 7

when a drug binds to both of the receptor sites on the channel and then causes it to open. this causes initial muscle spasms, but then the drug stays on the receptor and it stays open (aka the muscle stays depolarized) so the drug is now causing paralysis

Question 8

what kind of block does succinylcholine cause?

Answer 8

Phase I block

Question 9

what kind of block may result from high or prolonged doses of succinylcholine?

Answer 9

Phase II block

Question 10

How would an AChE inhibitor affect the actions of succinylcholine?

Answer 10

it would not change the action of succinylcholine at all because the amount of ACh present is irrelevant due to the fact that they are both agonists for the same receptor. The only thing that will affect this drug is time, when it comes off the receptor.

Question 11

what is the half life of succinylcholine? why?

Answer 11

very short because of plasma cholinesterase that rapidly metabolizes it

Question 12

do non-depolarizing agents cause muscle spasms?

Answer 12

no, they are not agonists, they do not depolarize the cell they just block it

Question 13

can non-depolarizing Nm receptor agents be affected by ACh concentration?

Answer 13

yes, they are not agonists, so they can be affected by the ACh which wants to activate the receptor