The process in the central nervous system aminergic synaptic terminals. It includes plasma membrane transporter, biosynthetic enzymes, vesicular transporters, and neurotransmitter storage in vesicles. Arrows indicate the flow of neurotransmitters into and out of the vesicles. The examples of cells contain secretory vesicles in peripheral tissues, including adrenal chromaffin granules, platelets storage granules, mast cells, enterochromaffin cells, and beta cells in pancreas. The diagram also includes chemical structures of dopamine, adrenaline, noradrenaline, serotonin, and histamine.
VMATs mediate the loading of monoamine neurotransmitters into synaptic vesicles and storage organelles. Monoamine neurotransmitters are synthesized in the cytosol and subsequently packaged into synaptic vesicles at nerve terminals or into storage organelles found in platelets, enterochromaffin, chromaffin, and other similar cells. When an action potential triggers calcium influx, these synaptic vesicles fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft. There, they bind to postsynaptic receptors, transmitting the signal. Signal termination is rapidly achieved by retrieval of the neurotransmitters, primarily mediated by specific Na+-coupled plasma membrane transporters. This crucial packaging of monoamines into vesicles is mediated by VMATs, specifically VMAT1 and VMAT2. VMAT1 is predominantly expressed in neuroendocrine cells, while VMAT2 is found throughout the central and peripheral nervous systems.