Cholinergic Transmission

Question 1

Synthesis of acetylcholine:

Answer 1

choline precursor is transporter into pre-synaptic nerve endings, transport is rate-limiting step in Each synthesis

Question 2

Storage of Acetylcholine:

Answer 2

ACh is transported into and stored in nerve terminal vesicles; uptake is mediated by H+-ACh antiporter

Question 3

Release of Acetylcholine:

Answer 3

arrival of action potential and depolarization of the terminal; influx of calcium and initiation of exocytosis

Question 4

What drug inhibits release of acetylcholine?

Answer 4

onabotulinumtoxin: Botulinum toxin

Question 5

T/F. Botulinum toxin is a protein.

Answer 5

TRUE.

Question 6

What is the mechanism of botulinum toxin?

Answer 6

is a protein that is taken up into cholinergic nerve terminals by receptor-mediated endocytosis; inactive synaptic vesicle protein required for vesicle docking with presynaptic membrane; produced reversible state of cholinergic denervation

Question 7

T/F. Botulinum toxin produces flaccid paralysis of skeletal muscle.

Answer 7

TRUE.

Question 8

What is the street name for botulinum toxin?

Answer 8

Botox.

Question 9

How is botox given and what is it used for?

Answer 9

IM, therapeutic uses for muscle spasms/dystonias, cosmetic, excessive perspiration, overactive bladder

Question 10

What are side effects of botox?

Answer 10

distant spread beyond injection site can cause serious dysphagia and breathing difficulties, allergic reactions, loss of facial expression

Question 11

What are the two cholinergic receptor subtypes?

Answer 11

muscarinic and nicotinic

Question 12

What are the most common muscarinic receptors?

Answer 12

M2 and M3 (there are M1-M5)

Question 13

Which drug selectively STIMULATES muscarinic receptors?

Answer 13

muscarine (agonist)

Question 14

Which drug selectively BLOCKS muscarinic receptors?

Answer 14

atropine (antagonist)

Question 15

What is an example of using atropine?

Answer 15

eye drops in the eye to dilate pupils; antagonists of muscarinic receptor = iris sphincter

Question 16

What are the most common nicotinic receptors?

Answer 16

Nn(neuronal, ganglia) and Nm(neuromuscular junction)

Question 17

How is the Nn (neuronal) different than Nm (neuromuscular)?

Answer 17

Nn = 2 alpha and 3 beta, Nm = 2 alpha, beta, GAMMA, and DELTA; nicotine ONLY stimulates Nn, whereas nicotine stimulates AND blocks in Nm

Question 18

If nicotine persistently blocks the Nn receptors what can occur?

Answer 18

desensitization (depolarizing blockade)

Question 19

What is a cholinergic antagonists (blocker) of Nn receptor?

Answer 19

mecamylamine

Question 20

What is a competitive antagonist of Nm

Answer 20

d-tubocurarine

Question 21

Termination of cholinergic transmission: acetylcholinesterase RAPIDLY terminate cholinergic transmission by what?

Answer 21

Hydrolysis (choline is recycled)

Question 22

Butyrylcholinesterase functions as what?

Answer 22

drug metabolizing enzyme

Question 23

What is a ganglionic blocking agent?

Answer 23

mecamylamine

Question 24

Characteristics of mecamylamine:

Answer 24

antihypertensive (lowers high BP); withdrawn from sales

Question 25

Mechanism of mecamylamine:

Answer 25

noncompetitive antagonist of Nn receptors; has no effect on Nm receptors; blocks activation of postganglionic PNS and SNS nerve fibers