Reuptake transporters can be present either pre- and/or postsynaptically. They take up the (excess) neurotransmitter present in the synaptic cleft, which is not bound to another receptor. This reuptake process thus lowers the concentration present in the synaptic cleft. Usually the neurotransmitter that has been taken up is metabolised by enzymes present in the synapse of postsynaptic neuron. Alternatively, the neurotransmitter can enter a synaptic vesicle and be released again.