Lack of effect of an early stressful life event on sensorimotor gating in adult rats

Hypotheses of the etiology of schizophrenia emphasize the important role of perinatal insults in predisposing individuals to the development of the disease, so that an animal model in which a discrete postnatal manipulation of the infant social environment yields schizophrenia-like behavior in adulthood would be valuable in terms of the study of the neural substrate and treatment of schizophrenia. Schizophrenics demonstrate a deficit in sensorimotor gating (prepulse inhibition), and a similar phenomenon has been described in adult rats following the administration of direct and indirect dopamine agonists. Recently it has been reported that a 24 h separation of rat pups from the mother results in a disruption of prepulse inhibition at adulthood. Here we report a study which investigated the same phenomenon but which, in contrast to the previous study, utilized unrelated subjects all derived from different dams. Maternal separation was conducted for 24 h with pups aged 4, 9 or 18 days and these subjects, together with non-separated controls, were tested at age 3 months in terms of their prepulse inhibition in the acoustic startle response paradigm. Maternal separation did not disrupt prepulse inhibition. Comparison of males and females (with a maximum of one opposite-sex sibling) demonstrated that acoustic startle response and prepulse inhibition of this response was enhanced in males relative to females. This study indicates that 24 h maternal separation does not provide a robust model for studying the effects of early environmental insults on the long-term abnormal development of sensorimotor gating.