Abstract
Human autism is comorbid with epilepsy, yet, little is known about the causes or risk factors leading to this combined neurological syndrome. Although genetic predisposition can play a substantial role, our objective was to investigate whether maternal environmental factors alone could be sufficient.
We examined the independent and combined effects of maternal stress and terbutaline (used to arrest preterm labor), autism risk factors in humans, on measures of both autistic-like behavior and epilepsy in Sprague-Dawley rats. Pregnant dams were exposed to mild stress (foot shocks at 1 week intervals) throughout pregnancy. Pups were injected with terbutaline on postnatal days 2–5.
Either maternal stress or terbutaline resulted in autistic-like behaviors in offspring (stereotyped/repetitive behaviors and deficits in social interaction or communication), but neither resulted in epilepsy. However, their combination resulted in severe behavioral symptoms, as well as spontaneous recurrent convulsive seizures in 45% and epileptiform spikes in 100%, of the rats. Hippocampal gliosis (GFAP reactivity) was correlated with both abnormal behavior and spontaneous seizures.
We conclude that prenatal insults alone can cause comorbid autism and epilepsy but it requires a combination of teratogens to achieve this; testing single teratogens independently and not examining combinatorial effects may fail to reveal key risk factors in humans. Moreover, astrogliosis may be common to both teratogens. This new animal model of combined autism and epilepsy permits the experimental investigation of both the cellular mechanisms and potential intervention strategies for this debilitating comorbid syndrome.
SIGNIFICANCE STATEMENT The comorbidity of human autism and epilepsy has been recognized for decades with little understanding of factors that increase risk. We show that two common human risk factors for autism (maternal stress and terbutaline), only when combined, result in severe ASD-like behavior and epilepsy. The significance of this work is fourfold: (1) combinations of teratogens are required to assess true risk in humans; (2) maternal stress and terbutaline, which are frequently combined in pregnant mothers, may be far more of a risk factor than previously appreciated; (3) astrogliosis may be a common mechanism for this syndrome; and (4) this first animal model of environmentally induced autism/epilepsy permits experimental investigation of cellular mechanisms and intervention strategies.
