Pyrethroids, a group of insecticides with high efficiency, low toxicity and wide spectrum, are used for pest control in agriculture. Here, we administered two representative pyrethroids (cypermethrin and deltamethrin) and an equal volume of vehicle (corn oil) to the pregnant ICR mice. This study investigated the effects of cypermethrin and deltamethrin on cerebral cortex development in mice as well as possible mechanisms in proliferation and differentiation. The results showed that histopathologic change did not occurred in the cerebral cortex using Hematoxylin and Eosin staining, however, the observation of fetuses exposed to cypermethrin and deltamethrin revealed reduction of neuronal proliferation, maturation and differentiation. Moreover, cypermethrin/deltamethrin-induced apoptosis of nerve cell was significantly higher in treated groups than that in control group by using flow cytometry, Western blot and TUNEL. It was worth mentioning that the newborns exposed to cypermethrin and deltamethrin did not showed abnormal neuronal distribution. These findings suggested that prenatal cypermethrin and deltamethrin exposure impaired corticogenesis.
