Comparative behavioral changes in postpubertal rats after neonatal excitotoxic lesions of the ventral hippocampus and the prefrontal cortex

The neonatal ventral hippocampal (nVH) and the neonatal prefrontal cortex (nPFC) lesions in rats have been used as models to test the hypothesis that early neurodevelopmental abnormalities lead to behavioral changes putatively linked to schizophrenia. We investigated the role of the nVH and the nPFC lesions on behavioral characteristics related to locomotor behaviors, social interaction, and grooming. Bilateral ibotenic acid lesions of the VH, the PFC, or both were made in neonatal Sprague-Dawley rats (postnatal day 7, P7) and their behaviors studied at P35 and P60. No significant differences in any of the behaviors were observed between sham animals and rats with ibotenic acid lesions at P35. Postpubertally (at P60), the spontaneous locomotor activity of nVH-lesioned rats was significantly enhanced compared to the sham controls; however, this hyperactivity was reversed by nVH and nPFC double lesions. Neonatal PFC lesion alone did not alter spontaneous activity, although a trend of increased activity was observed. The duration of grooming was significantly decreased in rats with neonatal lesions of the VH. Similar to the data on locomotion, nVH plus nPFC lesion normalized the grooming behavior. Lesion of the PFC alone was without any significant effect on grooming behavior. Neonatal VH-lesioned animals spent less time in active social interaction, and this effect persisted even in nVH plus nPFC-lesioned animals. By itself, nPFC lesion did not alter social behavior. These data suggest that subtle developmental aberrations within PFC caused by nVH lesions, rather than the lesion of PFC itself, may contribute to some of the behavioral changes seen in the nVH-lesioned rats. Synapse 56:147-153, 2005. (c) 2005 Wiley-Liss, Inc.