Effects of neurotensin administered into the ventral tegmental area on prepulse inhibition of startle.

Prepulse inhibition (PPI) of the acoustic startle reflex is an operational measure of sensorimotor gating. Both locomotor activity and PPI are regulated by mesolimbic dopamine activity. Neurotensin is a neuropeptide, which coexists with dopamine in mesolimbic neurons. Neurotensin receptors have been identified in the nucleus accumbens (NAC) and ventral tegmental area (VTA). Previous studies have shown that neurotensin administered into the NAC differentially modulates PPI and locomotor activity. In this study we tested the effects of neurotensin administered into the VTA on PPI and locomotor activity. Consistent with previous studies, intra-VTA administered neurotensin significantly increased spontaneous locomotor activity. However, intra-VTA administered neurotensin did not have any significant effect on PPI. These results suggest that PPI and locomotor activity may have dissociable mesolimbic substrates and that neurotensin in the VTA does not play an important role in regulating PPI.