Neurotensin is a 13 amino acid neuropeptide first isolated from bovine hypothalamus. It was detected in the central nervous system (CNS) and peripheral tissues mainly in the gastrointestinal tract, where it induces smooth muscle contraction. In the CNS, neurotensin has a dual function of neuromodulator of dopamine transmission and of anterior pituitary hormone secretion. It also shows potent hypothermic and analgesic effects in the brain. Neurotensin has been implicated in the pathophysiology of schizophrenia, Huntington, and Parkinson diseases. The intrastriatal perfusion with Neurotensin (1-13) [NT(1-13)] and its active fragment NT(8-13) on striatopallidal GABA leads to the increased striatal and pallidal GABA release, and this effect is antagonized by intrastriatal perfusion with the NT receptor antagonist. In other experiments, NT, NT (8-13) and [D-Tyr(11)] NT are applied into the ventral tegmental area on extracellular dopamine in the prefrontal cortex and nucleus accumbens of rats. In the prefrontal cortex, neurotensin (8-13) is as potent as neurotensin but ineffective in [D-Tyr(11)]neurotensin. In the caudal nucleus accumbens, neurotensin (8-13) and neurotensin appears more potent than [D-Tyr(11)]neurotensin. In contrast, in the rostral nucleus accumbens, neurotensin(8-13) is less potent than [D-Tyr(11)]neurotensin and neurotensin.