Neurotransmitters are the body’s chemical messengers. Each neurotransmitter can bind only to a very specific matching receptor in much the same way that a key can fit only into a matching lock. 

After neurotransmitters have delivered their message, they need to be removed from the synaptic cleft. Clearing the neurotransmitters from this space can happen in one of three ways. 

1. The neurotransmitters may undergo degradation in which they are broken down by enzymes within the synapse, rendering them unrecognizable and unable to bind to the receptor cell. 
2. The neurotransmitters may be reabsorbed into the presynaptic neuron from which they originated to be reused at a later time in a process known as reuptake. 
3. The neurotransmitters may fade away through the process of diffusion.