Aims: 

Neurotensin (NT) is a brain-gut peptide, which plays an important role in modulation of neurotransmission. Earlier investigations showed that NT modulates dopaminergic transmission in numerous brain structures. The ventral pallidum (VP) is innervated by the mesolimbic dopaminergic system and is important in motivation, reward and memory processes. We investigated the effects of NT and NTS-1-receptor antagonist injected bilaterally (in 0.4 ml) into the VP in conditioned place preference (CPP) test in male Wistar rats.

Methods: 

The CPP paradigm started with a habituation period. In the three following days conditioning sessions were carried out. During the test period, the time spent in the treatment quadrant was measured. In the first experiment 100 ng or 250 ng NT (Sigma-Aldrich Co., N 3010) were microinjected into the VP. Control animals received only vehicle. In the second experiment we investigated the effects of 35 ng dose of specific NTS-1-receptor antagonist SR48692 (gifted by Sanofi-Synthelabo Co.) equimolar with 100 ng NT. The antagonist was injected alone or 15 minutes before 100 ng NT treatment.

Results: 

100 ng dose of NT induced CPP, animals injected with 250 ng NT showed only a tendency to spend more time in the treatment quadrant. The effect of NT was inhibited by antagonist pretreatment, while the antagonist applied in itself had no effect.

Conclusion: 

Our results show that NT, injected into the VP, plays an important role in positive reinforcement. This effect is specific to NTS-1-receptors because it can be inhibited by specific antagonist.

Support: 

NKTH-OTKA K68431 and the HAS.