Neurotensin: a new 'reward peptide'.

oeurotensin (NT) is a tridecapeptide which is thought to bind to receptors located on dopamine cells in the ventral tegmental area (VTA). Rats with cannulas implanted in the VTA showed a significant increase in time spent in an environment in which they had received bilateral injections of neurotensin on previous days. This is indicative of conditioned reinforcement in which the neuropeptide was the primary reinforcer. In order to determine the specificity of neurotensin receptor interactions, 3 fragments of the peptide were examined at 2 doses. NT1-8 and NT8-13 were found to be inactive while NT1-11 demonstrated significant activity. The results suggest that NT in the VTA is capable of inducing reinforcing effects. This is the first evidence for a non-opiate 'reward peptide'.