What happens to acetylcholine after it has interacted with receptors on the post-synaptic neuron during exchange of signal from neuron to neuron?

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"Acetylcholine (ACh) is a simple molecule synthesized from choline and acetyl-CoA through the action of choline acetyltransferase. Neurons that synthesize and release ACh are termed cholinergic neurons. When an action potential reaches the terminal button of a presynaptic neuron a voltage-gated calcium channel is opened. The influx of calcium ions, Ca2+, stimulates the exocytosis of presynaptic vesicles containing ACh, which is thereby released into the synaptic cleft. Once released, ACh must be removed rapidly in order to allow repolarization to take place; this step, hydrolysis, is carried out by the enzyme, acetylcholinesterase. The acetylcholinesterase found at nerve endings is anchored to the plasma membrane through a glycolipid. " http://web.indstate.edu/thcme/mwking/nerves.html "Normally, the enzyme acetylcholinesterase converts acetylcholine into the inactive metabolites choline and acetate. This enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function. The devastating effects of organophosphate-containing nerve agents (e.g. Sarin gas) are due to their irreversible inactivation of this enzyme. The resulting accumulation of acetylcholine causes continuous stimulation of the muscles, glands and central nervous system; victims commonly die of suffocation as they cannot contract their diaphragm. Other organophosphates and some carbamates are effective insecticides because they inhibit acetylcholinasterase in insects. On the other hand, since a shortage of acetylcholine in the brain has been associated with Alzheimer's disease, some drugs that inhibit acetylcholinesterase are used in the treatment of that disease" http://en.wikipedia.org/wiki/Acetylcholine Feb 27 07, 6:31 PM