CCK and Parkinson disease: There have been reports of a number of changes in the concentrations of several neuropeptides in PD brain, which are mainly significant decreases in (Jiménez-Jiménez, 1994): (a) met-enkephalin (MET-ENK), substantia P (SP), and cholecystokinine 8 (CCK-8) in the substantia nigra; (b) MET-ENK and leu-enkephalin (LEU-ENK) in the putamen and globus pallidus; (c) MET-ENK in the ventral tegmental area; (d) SP, somatostatin and neurotensin in the neocortex, and (e) somatostatin and neurotensin in the hippocampus.