The regulated exocytotic release of neurotransmitters in response to neural activity requires storage within intracellular vesicles. In the nervous system, these vesicles are the synaptic vesicles that are derived from the endosomal compartment, whereas in endocrine cells larger secretory granules, such as the chromaffin granules of adrenal medulla, are derived from the trans golgi networks. For classical transmitters that are synthesized in the cytoplasm or appear there after removal form the synapses by plasma membrane reuptake, storage depends upon the active transport into the vesicles. Several distinct transport activities have been identified for monoamines, acetylcholine, glutamate, GABA and glycine. Vesicular monoamine transporters (VMATs) catalyze transport and storage of monoamines, serotonin, dopamine, norepinephrine, epinephrine, and histamine.