Nictotinic Acetylcholine Receptor (nAChR)

Question 0

Function

Answer 0

Non-selective cation channel, allows Na and other cations, strictly impermeable to anions. Results in depolarization and AP in neurons and muscle cells

Question 1

Subfamily

Answer 1

Pentametric Ligand-gated Receptors (GABAaR, GlyR, and 5-HT3R)

Question 2

Agonists

Answer 2

ACh, Nicotine, Choline, carbachol, etc

• Needs two molecules of ACh to bind for activation
• Dissociation of ACh is slow, so channel may open and close several times before the ACh is removed
• Agonist usually remain bound until the channel closes, then they leave.

Question 3

Antagonists

Answer 3

alpha-bungarotoxin (snake venom), tubocurarine (arrow head poison for South American Indians) - Competitively and irreversibly block nAChR = spastic paralysis, respiratory failure, and death.
*Synthesized antagonists include mecamylamine and memantine.

Question 4

Desensitization

Answer 4

Prolonged or repeated exposure to ACh can result in desensitization and lack of response. Can also desensitize due to receptor phosphorylation by PKA or PKC

Question 5

Neuromuscular Junction

Answer 5

ACh usually acts as a messenger at the neuromuscular junction, results in depolarization of the muscle cell and generation of an AP.

Question 6

nAChR in the CNS

Answer 6

Endogenous ACh and exogenous nicotine facilitate DA release in the brain (elevating mood)
Mecamylamine is a non-competative antagonist used for smoking cessation