Figure 1.

Acetylcholine synthesis and degradation, and the actions of pharmacological interventions. Acetylcholine (ACh) is synthesized in neurons from choline and acetyl-coenzyme A by the enzyme acetyltransferase. ACh is protected from degradation by packaging within synaptic vesicles. ACh is released into the synaptic cleft where it acts upon pre- and postsynaptic muscarinic and nicotinic receptors, and degraded into choline and acetate by the enzyme acetylcholinesterase (AChE). Choline is recycled back into neurons. AChE inhibitors (AChEIs) such as physostigmine and donepezil prevent the breakdown of ACh. Precursors such as deanol and choline contribute to ACh synthesis. Abbreviations: AcCoA, acetyl coenzyme A; AChR, acetylcholine receptor.