Specific transporter proteins called monoamine transporters exist that transport monoamines in or out of a cell. These are the dopamine transporter (DAT), serotonin transporter (SERT), and the norepinephrine transporter (NET) in the outer cell membrane and the vesicular monoamine transporter (VMAT1 and VMAT2) in the membrane of intracellular vesicles.
Monoamine oxidase is an enzyme that breaks down monoamine neurotransmitters after they have been released into the synapse.