Answer
There are three processes by which neurotransmitters (NT) released into synaptic clefts are removed:
The first is simple diffusion. Some of the unbound NT in the synaptic cleft just diffuses into the surrounding interstitial fluid. The dilution causes it to lose its potency. Second, there is enzymatic degradation. In this case specific enzymes decompose and deactivate released, unbound neurotransmitter molecules. In the case of the neurotransmitter acetylcholine (ACH) the degradation is accomplished by the enzyme acetylcholinesterase.
Work Step by Step
The process of uptake (and reuptake) also functions to shorten the period of released NT activity on postsynaptic membranes: neuroglia are known to take up released norepinephrine; addition some neurotransmitter molecules are reabsorbed (reuptaken) into the cells that released them.
