Acetylcholine

[WG21:p101-103]

=== Unfinished ===

Need to consolidate and re-organise some of the stuff from [Neuromuscular junction], [Acetylcholine] and [Receptors]

Botulinum toxin works by inhibition of ACh synthesis and release [???]

======

• Acetylcholine is acetyl ester of choline

Synthesis of acetylcholine

Reaction
= Choline + Acetyl-CoA --> Acetylcholine --> Choline + Acetate

NB:

• Acetylcholine, after formation, is taken up into synaptic vesicles by a vesicular transporter VAChT

Enzymes involved

• Formation of acetylcholine is catalysed by choline acetyltransferase
  * High concentration in cytoplasm of cholinergic nerve endings
• Breakdown of acetylcholine is catalysed by acetylcholinesterase

NB:

• Choline is actively taken up via a transporter into cholinergic neurons
  * The transporter is a sodium dependent carrier protein, blocked by hemicholinium [BGK9:p78]
• Choline is also synthesised in neurons

Catabolism of acetylcholine

• Acetylcholine is rapidly broken down in the synapse
  * By hydrolysis which is catalysed by acetylcholinesterase
  * Into choline and acetate
  * Choline is actively taken up by the motor nerve ending
• Acetylcholinesterase is located in neuromuscular junction
• ACh is also broken down by plasma cholinesterase to lesser extent [SH4:p263]