Co-storage in large ‘dense-core’ vesicles of dopamine and cholecystokinin in rat striatum

The subcellular localization of cholecystokinin in the striatum—an area where a high density of cholecystokinin containing terminals has been demonstrated—was studied using biochemical techniques. Cholecystokinin containing vesicles were partially purified using iso-osmotic Ficoll gradients. As judged from their size and their buoyant density in isopycnic gradients, cholecystokinin containing vesicles represent large ‘dense-core’ vesicles. Negative staining and subsequent immunolabelling for synaptophysin at the electron microscopical level, showed labelled vesicles of 50–70 nm. Binding of dihydrotetrabenazine was detected in the cholecystokinin containing fractions. The results suggest that dopamine is co-stored with cholecystokinin in large dense vesicles in rat striatum.