Acetylcholine (ACh)

Question 1

What is ACh?

Answer 1

Primary NT secreted by efferent neurons in CNS

Question 2

What is the role of ACh?

Answer 2

Facilitation - ACh and terminal buttons distributed widely throughout the brain

Question 3

Three ACh systems/structures involved

Answer 3

Dorsolateral pons
Basal forebrain
Medial Septum

Question 4

Dorsolateral pons

Answer 4

Involved in eliciting most of the characteristics of REM sleep

Question 5

Basal forebrain

Answer 5

General activation of cortex and facilitation of learning, especially perceptual learning

Question 6

Medial septum

Answer 6

Regulate electrical rhythms of hippocampus, important in formation of certain kinds of memories

Question 7

How is ACh deactivated?

Answer 7

2. Ach is deactivated in post-synaptic receptor by enzyme AchE – acetate and choline
   - choline is taken up into pre-synaptic button

Question 8

Two types of ACh receptors

Answer 8

Nicotinic and Muscarinic

Question 9

Nicotinic

Answer 9

ionotropic (thus rapid firing) – neuromuscular junctions, some in CNS

• neuromuscular junctions and skeletal muscle, some in CNS
• Agonist: ACh, nicotine
• Antagonists: d-tubocurarine and curare (induce paralysis)
• Myasthenia gravis - less nicotinic receptors, less ACh

Question 10

Muscarinic

Answer 10

metabotropic (slower firing) – predominate in CNS

• In heart and smooth muscle, predominate in CNS
• Agonists: ACh, muscarine
• Antagonists: atropine and scopolamine

Question 11

Drug interactions

Answer 11

• botulinum toxin – blocks protein that causes fusion of nt vesicle with pre-synaptic membrane
• black widow venom – binds with protein and causes release of Ach
• curare – blocks nicotinic receptors and produces paralysis, used in “poison darts” and in surgery
• Acetylcholinesterase inhibitor - Aricept (donepezil - Alzheimer’s )

Question 12

Botulism toxin

Answer 12

ACh release blocked by botulism - blocks protein that causes fusion of NT vesicles w/ presyn mem