Developmental and behavioral effects of prenatal amitraz exposure in rats.

The effects of prenatal amitraz exposure on physical and behavioral parameters of rats were studied. Pregnant rats were orally gavaged with amitraz (20 mg/Kg) or with distilled water (1.0 ml/Kg) on Days 1, 4, 7, 10, 13, 16, and 19 of pregnancy. After birth, cross-fostering was performed thus generating the following groups: control pups nursed by control dams (CC); control pups nursed by treated dams (CE); treated pups nursed by treated dams (EE) and treated pups nursed by control dams (EC). Results show that compared to pups of Group CC, groups prenatally exposed to amitraz (EC and EE) showed decreased age of vaginal opening. Group EE also showed earlier fur development and a delay in incisor eruption compared to Group CC. The ages of pinna detachment, eye and ear opening, testes descent, and reflex development (surface righting and startle) were not affected by amitraz exposure. Offspring of group CE also showed earlier fur development. Rats of group EE had higher locomotor activity and rearing frequency and shorter immobility time compared to the rats of group CC when observed in an open-field 30 days after birth but not 60 and 90 days. No significant differences were found in open-field behaviors among the CC, CE, and EC groups. The present findings indicate that prenatal exposure to amitraz caused transient developmental and behavioral changes in the exposed rat offspring and suggest that further investigation of the potential health risk of amitraz exposure to developing human offspring may be warranted.