REDUCED PREPULSE INHIBITION AFTER ELECTROLYTIC LESIONS OF NUCLEUS-ACCUMBENS SUBREGIONS IN THE RAT

A variety of neurochemical and anatomical studies have shown that the ventral striatal nucleus accumbens (NAcc) can be divided into a predom inantly medial 'shell' and a predominantly lateral 'core'. These accum bens subdivisions are innervated by different cortical regions and pro ject to different anatomical targets. Additionally, recent behavioral observations suggest functional differences between the accumbens shel l and core. In order to further examine core and shell function, we me asured prepulse inhibition (PPI) of the acoustic startle reflex after electrolytic lesions aimed at the central NAcc, the NAcc shell, the NA cc core, and the adjacent anteroventrolateral striatum. Acoustic start le is the contraction of whole-body musculature in response to a sudde n, loud auditory stimulus, and PPI is the inhibition of acoustic start le by a weak auditory 'prepulse' administered 30-500 ms prior to the s tartling stimulus. Previous work has shown that PPI is regulated by th e NAcc, and recent observations suggest that PPI is regulated by diffe rent neurochemical interactions in the core and shell. PPI was signifi cantly reduced by electrolytic lesions of the central NAcc, as well as by lesions that predominantly damaged-either the NAcc shell or the co re. Lesions of the anteroventrolateral striatum and lateral edge of th e NAcc core did not significantly alter PPI. These findings suggest th at, despite neurochemical differences between the two subregions, PPI is regulated by both the NAcc shell and core. (C) 1997 Elsevier Scienc e B.V.