Maternal deprivation in the middle of a stress hyporesponsive period decreases hippocampal calcineurin expression and causes abnormal social and cognitive behaviours in adult male Wistar rats: Relevance to negative symptoms of schizophrenia

Adverse experiences in early life profoundly influence the developing nervous, endocrine, and immune systems, and also affect human behaviour during adult life and are considered in the pathogenesis of psychiatric disorders. Numerous studies have provided evidence that maternal deprivation in the middle of a stress hyporesponsive period (SHRP) causes multiple behavioural and physiological abnormalities that mimic positive symptoms of schizophrenia in humans. To investigate the neurochemical characteristics of maternal deprivation in the middle of the SHRP in the context of a possible animal model of the symptoms of schizophrenia, we examined calcineurin expression in the hippocampus of maternally deprived rats. To investigate other behavioural characteristics, we behaviourally phenotyped the rats by applying a comprehensive behavioural test battery. The results indicate that maternal deprivation in the middle of the SHRP has no effects on general health, neurological reflexes, sensory function, or motor function, but does have sex-specific effects on a type of anxiety-related behaviour in the open field test and male-specific effects on hippocampal calcineurin expression, social behaviour, and objective memory function. An interpretation of our results and previous studies in the context of the neurodevelopmental hypothesis of schizophrenia suggests that maternal deprivation in the middle of the SHRP in rats models some positive and negative aspects of schizophrenia. The findings regarding the sex-specific effects of maternal deprivation in the middle of the SHRP may become a strong tool for investigating sex differences in the pathogenesis and pathology of schizophrenia in humans.

► We examine the effects of maternal deprivation in the middle of the SHRP in rats.
► It has no effects on fundamental behavioural functions.
► It has sex-specific effects on anxiety-related behaviour.
► It has male-specific effects on hippocampal calcineurin expression.
► It has male-specific effects on social behaviour and objective memory function.