The effects of combined prefrontal cortical and hippocampal damage on dopamine-related behaviors in rats.

The effects of excitotoxic damage to both the medial prefrontal cortex (MPFC) and the ventral hippocampus (VH) on behaviors related to mesolimbic/nigrostriatal dopamine (DA) transmission were investigated in the rat. Locomotor activity in a novel environment, after injection of saline, and after d-amphetamine was assessed 2 and 4 weeks after ibotenic acid lesion of both MPFC and VH in adult rats. In addition, stereotypic behaviors and locomotion after apomorphine were evaluated 8 weeks after the lesion. Locomotor activity was significantly enhanced in all testing conditions in lesioned rats as compared with sham-operated animals, while oral stereotypic behaviors elicited by apomorphine were attenuated possibly because they were eclipsed by excessive locomotion. These data indicate that coexisting lesions of the MPFC and VH in adult rats produce potent and long-lasting effects on behaviors believed to be dependent primarily on the mesolimbic DA system. The profile of changes resembles more closely that observed after excitotoxic lesions of the VH alone rather than that after separate MPFC lesion.