1. Diffusion: the neurotransmitter drifts away, out of the synaptic cleft where it can no longer act on a receptor.
Diffusion
2. Enzymatic degradation (deactivation): a specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor. For example, acetylcholinesterase is the enzyme that breaks acetylcholine into choline and acetate.
Enzymatic degradation
3. Glial cells: astrocytes remove neurotransmitters from the synaptic cleft.
Astrocyte
4. Reuptake: the whole neurotransmitter molecule is taken back into the axon terminal that released it. This is a common way the action of norepinephrine, dopamine and serotonin is stopped...these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors."
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