Developmental neurotoxicity of inorganic arsenic exposure in Sprague-Dawley rats

High levels of inorganic arsenic (iAs) exposure are associated with severe health effects. Less clear are effects of lower exposure levels on neurodevelopment. Relative to maternal intake, there is limited lactational transfer of arsenic in humans or rodents, yet there are few rodent studies which directly exposed preweaning animals. To more clearly determine iAs developmental neurotoxicity, 28 pregnant Sprague-Dawley rats were exposed to arsenate (AsV) via drinking water (0, 23.6, 47.7, 71.0 ppm) (n = 5-7/group) from gestational day (GD) 6 through GD 22 with targeted doses of 0, 2.33, 4.67, 7.00 mg/kg/day, respectively. Offspring were dosed by gavage daily with the same mg/kg AsV dose as intended for their dam from postnatal day (PND) 1 to 21. Gestational water intake was reduced at all AsV doses, but returned to control levels on lactational day (LD) 1 when control water was returned. Gestational body weight was reduced only at the highest dose on GD 22 and lactational body weight was unaffected. Food intake was unaffected. iAs exposure did not alter offspring body weight (PNDs 1-21) or age at fur development and bilateral ear opening. Incisor eruption, however, was significantly delayed in offspring of the 4.67 and 7.00 mg/kg groups. Further, all iAs groups were significantly delayed in bilateral eye opening. Righting reflex (PNDs 3-6) was unaffected, while slant board performance (PNDs 8-11) was significantly poorer at the highest dose. Brains of culled pups (PND 1) showed dose-dependent increases of iAs. There were no significant AsV-related effects on PND 21 brain regional concentrations of dopamine, DOPAC, HVA, 5-HT or 5-HIAA. These hazard identification results will guide the study designs of developmental iAs exposure at human-relevant levels essential for risk-assessment.