Involved in the transport of biogenic monoamines, such as serotonin, from the cytoplasm into the secretory vesicles of neuroendocrine and endocrine cells. Strongly inhibited by reserpine. Also inhibited to a lesser extent by ketanserin and fenfluramine. Not significantly inhibited by tetrabenazine. Highly expressed in chromaffin cells of the adrenal medulla (at protein level). Detected in peripheral sympathetic ganglia (at protein level). Found in some paracrine cells in stomach and duodenum (at protein level). Unable to uptake serotonin. Belongs to the major facilitator superfamily. Vesicular transporter family.