Neuroactive peptides exist in the midbrain dopaminergic neurons that contain calbindin-D28k.

Calbindin-D28k, a calcium-binding protein, has been identified within a subpopulation of midbrain dopaminergic (DA) neurons in rats, monkeys and humans. The neuroactive peptides CCK and neurotensin also have been found in a subpopulation of midbrain DA neurons. Using double- and triple-labeling immunocytochemical staining procedures in the rat, we now report that the midbrain DA neurons that contain the peptides also contain calbindin-D28k. Calbindin-D28k may play a role in the co-release of neuroactive peptides with dopamine from the midbrain DA neurons.