Pyrethroid insecticides and pregnancy: effect on physical and behavioral development of rats.

We investigated the prenatal effects of cyhalothrin exposure on the physical and behavioral development of infant and adult rats. Female rats were treated by dermal exposure with a 0.018% cyhalothrin aqueous solution (1 ml/d) or the cyhalothrin vehicle during their entire pregnancy. The pesticide delayed development of fur, the ear and eye openings and descent of the testes in the offspring. The exploratory behavior of the rats prenatally exposed to cyhalothrin decreased. No differences were observed between control and experimental animals in inhibitory avoidance tasks at 90 d of age in open field activity. Alterations in physical parameters and possible effects of the pesticide on epidermal growth factor and hormonal levels were considered. Since no overt of signs of maternal or neonatal toxicity were observed, the decrease in adult motivational behavior was attributed to a specific effect of the pesticide administered during the prenatal period. We concluded that prenatal cyhalothrin exposure induced subtle and persistent changes in the physical development and behavior of rats.