Behavioral teratogenicity of valproic acid: selective effects on behavior after prenatal exposure to rats.

Pregnant Sprague-Dawley rats were treated with 0, 150 or 200 mg/kg valproic acid by gavage (VPA) on days 7-18 of gestation. These doses produced no maternal toxicity, reproductive effects or effects on offspring growth and survival. Maternal plasma VPA peak levels averaged 99 and 134 micrograms/ml 1 h after the last treatment, values approximating human therapeutic levels. VPA offspring tested after weaning exhibited reduced open-field central, but not peripheral, activity and reduced hole-board horizontal, but not vertical, activity. No activity differences were found in a figure-8 test or a preweaning activity test. The VPA offspring also showed lengthened straight channel swimming times, increased swimming maze errors, but only among the females, while producing no differences in maze times. VPA offspring exhibited reduced spontaneous alternation frequency and reduced startle responding to both auditory and tactile (air-puff) stimuli. The effects of VPA were dose dependent in some cases (straight channel swimming and water maze errors), or the effect was seen only in the high-dose group (open-field, hole-board, spontaneous alternation, startle). The conclusion was reached that prenatal VPA is behaviorally teratogenic in rats at relevant maternal blood concentrations and at non-malforming doses.