Acetylcholine is the neurotransmitter found at neuromuscular junctions, synapses in the ganglia of the visceral motor system, and at a variety of sites within the central nervous system. A great deal is known about the function of cholinergic transmission at the neuromuscular junction and at ganglionic synapses, the actions of ACh in the central nervous system are not as well understood. Acetylcholine is synthesized in nerve terminals from acetyl coenzyme A (acetyl CoA) synthesized from glucose) and choline. This reaction is catalyzed by choline acetyltransferase (CAT). The presence of acetyltransferase in a neuron is thus a strong indication that ACh is used as one of its transmitters. Choline is present in plasma at a concentration of about 10 mM, and is taken up into cholinergic neurons by a high-affinity Na+/choline transporter. About 10,000 molecules of ACh are packaged into each neurotransmitter containing vesicle by a vesicular ACh transporter.