Disruption of latent inhibition in rats with postnatal hippocampal lesions

Disruption of latent inhibition has been proposed as a possible model of co gnitive abnormalities that under lie positive symptoms of a schizophrenia. We tested neonatal hippocampal lesioned vats in a Intent inhibition paradig m. Lesions of the ventral hippocampus were induced by bilateral injections of ibotenic acid in 7 days old mts. The behavior of lesioned was was tested postpubertally. We found a hyperresponsiveness to dopaminergic stimulation by apomorphine in locomotion tests. Latent inhibition was tested using the acquisition of a conditioned reaction in a two-way shuttle box. Sham opera ted control animals showed after preexposure of the to-be-conditioned stimu lus (combined tone and light stimulus) a low acquisition. Ibotenic acid les ioned animals learned the conditioned reaction with and without preexposure in the same way, indicating disturbed latent inhibition. These results dem onstrate disturbances in early postnatal hippocampal lesioned rats comparab le with those seen in schizophrenic patients, thus further validating this procedure as a useful animal model of some aspects of schizophrenia. (C) 19 99 American College of Neuropsychopharmacology. Published by Elsevier Scien ce Inc.