Prenatal exposure to dichlorvos: physical and behavioral effects on rat offspring

The effects of prenatal exposure to dichlorvos (DDVP), an organophosphate (OP) pesticide, on pups' physical and neurobehavioral developments were investigated. Forty pregnant rats were treated by gavage with 8.0 mg/kg DDVP or its vehicle (1 ml/kg) from the 6th to the 15th day of pregnancy. At birth, pups were weighed, the litters culled to eight animals (four male and four female), and then observed for physical (pinna detachment, incisor eruption, eye opening, testes descent, and vaginal opening) and neurobehavioral developments (palmar grasp, surface righting, negative geotaxis, and open-field behaviors). As adults, open-field, apomorphine-induced stereotypy, and passive avoidance behaviors were also assessed. Results showed no differences between the body weight of DDVP and control-treated groups. No differences were observed on the measures of physical and neurobehavioral development. Locomotor activity of male pups at 21 days of age was decreased by DDVP exposure. Adult experimental offspring showed a decreased locomotor frequency and an increased immobility duration on open-field behavior in relation to control animals; the apomorphine-induced stereotyped behavior was decreased by the pesticide exposure as well as performance on the passive avoidance task. These data suggest that prenatal DDVP exposure was able to decrease offspring motor function (adolescence and adults) and conditioned response learning, probably by interference with the cholinergic-dopaminergic balance of activity involved with the control of motor function as well as the cholinergic system that modulates learning process.