Neurotensin (NT) is a 13-amino-acid peptide [69] that is widely distributed in neurons, in which, in dense nuclear vesicles, it acts as a neuromodulator of several neurotransmitters, such as acetylcholine, as well as serotonin, GABA, and dopamine [70].The IHC of normal rat brains showed the expression of NT in ventral tegmental-area fibers and SN (both compacta and reticulata) [71], while combined HPLC/RIA showed an increased (twofold) expression in post-mortem SN samples from 6 advanced-PD patients (compared to 5 controls) [72]. This evidence concerns the gene NTS and Parkinson disease.