Perinatal toxicity of endrin in rodents. III. Alterations of behavioral ontogeny

The behavioral development of rats and hamsters was observed following perinatal exposure to endrin, a central nervous system teratogen in the hamster but not the rat [1,2]. In the hamster, prenatal exposure to endrin at 1.5 mg/kg/day on days 5-14 of gestation produced a persistent elevation in the locomotor activity. Offspring of treated hamsters ambulated 75% more than controls in the open field at 15 days and 45% more at 20 days of age. Long term observations of locomotor activity in the figure-8 mazes indicated that a significant elevation of this behavior was still present at 125 days of age. Non-locomotor behaviors of the Offspring (including sexual, rearing and running wheel behaviors) were unaffected. The dams repeatedly exposed daily to endrin at 0.75 or 1.5 mg/kg/day were markedly hypoactive using the same testing conditions in which the pups were hyperactive. This dosing regime was toxic to the dams in the 1.5 mg/kg/day dose group, killing more than half of them. In the second experiment, rats exposed perinatally to endrin at 0.15 or 0.30 mg/kg/day were 30% more active than control prior to weaning, but not as adults. These doses did not kill dams or affect the pup survival or growth. The similarity of the behavioral changes noted in the young of both species is suggestive of similar alteration of central nervous system function even though endrin produces gross morphological defects only in the hamster.