Neurobehavioral teratogenic effects of thalidomide in rats.

Thalidomide-induced embryopathy has been known for four decades, however, the drug has been reintroduced for human use in a number of countries, including the United States. In utero thalidomide exposure in humans is associated with central nervous system (CNS) effects in addition to the well-known limb, ear and other malformations. Despite knowledge of these CNS effects, not a single experimental study could be found that examined thalidomide for possible developmental neurobehavioral effects. In the present experiment, gravid Sprague-Dawley rats were treated with either thalidomide (100 mg/kg by gavage) or vehicle (propylene glycol) on embryonic days E7-18 and allowed to deliver and raise their own offspring. The offspring were evaluated in a series of neurobehavioral tests (reflexes, locomotor activity, startle reactivity and learning in the Morris and Cincinnati water mazes). There was a small reduction in maternal weight among thalidomide-treated dams during midgestation. Thalidomide offspring showed increased preweaning mortality and male-specific, late onset reduction in growth that persisted until the end of the study. Male thalidomide offspring showed significant increases in errors and latency in the multiple-T Cincinnati water maze. Although rats are refractory to thalidomide-induced teratogenesis, the present results suggest that thalidomide selectively impairs offspring survival and growth and at least one type of learning among male offspring.