Nonexploratory movement and behavioral alterations in a thalidomide or valproic acid-induced autism model rat

Autism is a behaviorally characterized disorder with impairments in social interactions, as well as stereotyped, repetitive patterns of behaviors and interests. Exposure of rat fetuses to thalidomide (THAL) or valproic acid (VPA) on the ninth day of gestation has been reported as a useful model for human autism. We have shown that early serotonergic neural development is disrupted in these rats. In the current study, we used a radial maze and open field experimental paradigm to investigate whether these rats present behavioral and/or learning aberrations. THAL (500 mg/kg), VPA (800 mg/kg), or vehicle was administered orally to E9 pregnant rats at 7–10 weeks of age. Although the mean number of correct and incorrect arm choices in the initial eight arm choices did not differ between control and teratogen-exposed groups, achievement of learning (seven or eight consecutive correct choices for 3 consecutive days for individual rats) seemed to be impaired in teratogen-exposed groups. Interestingly, average time to explore the maze task was shorter in the teratogen-exposed groups, indicating that correct choice might be due to mere coincidence (i.e., nonexploratory movement). Unexpectedly, no significant differences were observed in social interaction in these rats. These results indicate that prenatal exposure to THAL and VPA might alter behavior in a manner that is, in part, consistent with human autism.