Which statement best describes acetylcholine degradation and recycling?

• A. Acetylcholine is hydrolyzed by acetylcholinesterase into acetic acid and choline, and choline is recycled into the presynaptic neuron
• B. Acetylcholine is never degraded and remains active in the synaptic cleft
• C. Acetylcholine is converted into dopamine
• D. Acetylcholine is stored in vesicles unchanged after release

Answer: (A)

When acetylcholine is released at a cholinergic synapse, it is rapidly inactivated by the enzyme acetylcholinesterase in the synaptic cleft, which breaks it down into acetate and choline. The choline is then transported back into the presynaptic neuron, where it’s reused to synthesize new acetylcholine with acetyl-CoA. This combination of degradation and recycling is what terminates the signal quickly and maintains a ready supply of transmitter for the next release.

That description matches the best answer because it accurately describes both the breakdown by acetylcholinesterase and the recycling of choline into the presynaptic neuron for resynthesis of acetylcholine. The other statements are inconsistent with how acetylcholine signaling is terminated and recycled: it is not left active in the cleft, it is not converted into dopamine, and it is not stored unchanged after release.