Social behaviour in rats lesioned with ibotenic acid in the hippocampus: quantitative and qualitative analysis

Rationale: Neonatal ibotenic acid lesion of the ventral hippocampus was pro posed as a relevant animal model of schizophrenia reflecting positive as we ll as negative symptoms of this disease. Before and after reaching maturity , specific alterations in the animals' social behaviour were found. Objecti ve: In this study, social behaviour of ventral hippocampal lesioned rats wa s analysed. For comparison, rats lesioned either in the ventral hippocampus or the dorsal hippocampus at the age of 8 weeks were tested. Methods: Rats on day 7 of age were lesioned with ibotenic acid in the ventral hippocampu s and social behaviour was tested at the age of 13 weeks. For comparison, a dult 8-week-old rats were lesioned either in the ventral or the dorsal hipp ocampus. Their social behaviour was tested at the age of 18 weeks. Results: It was found that neonatal lesion resulted in significantly decreased time spent in social interaction and an enhanced level of aggressive behaviour. This shift is not due to anxiety because we could not find differences bet ween control rats and lesioned rats in the elevated plus-maze. Lesion in th e ventral and dorsal hippocampus, respectively, in 8-week-old rats did not affect social behaviour. Conclusions: The results of our study indicate tha t ibotenic acid-induced hippocampal damage per se is not related to the shi ft in social behaviour. We favour the hypothesis that these changes are due to lesion-induced impairments in neurodevelopmental processes at an early stage of ontogenesis.