Neurobehavioral Effects of Lead and Manganese in Developmentally‐Exposed Rats: A Comparative Study between Individual and Combined Exposures

Lead (Pb) and manganese (Mn) are known neurotoxic metals, and effects of exposure to environmentally relevant low levels are of interest. As the developing brain is highly susceptible to neurotoxic insult, effects of exposure during this period are of vital importance. Pregnant CD rats were exposed to drinking water salt solutions of Pb (10 μg/ml), Mn (2 mg/ml) or a mixture, from beginning of gestation, through lactation until weaning. Behavior tests began after weaning (PND 21–25), and were repeated 1 month later (PND 56–60). Female pups exposed to the metal mixture had significantly higher body weights through PND 28, and faster surface righting reflexes. At PND 24, mixture‐exposed females were hyperactive while Mn‐exposed pups were hypoactive in an open field. These effects were not evident at PND 59. Four day Morris water maze tests were performed, ending with probe trials on PND 25 and 60. At PND 24, mixture‐exposed males performed significantly better, while Mn‐exposed males showed deficits in learning and memory. These effects were also seen on PND 58 and 59. Developmental exposures to low Pb and Mn levels can produce gender‐specific neurobehavioral deficits, with some effects persistent after cessation of exposures. Effects due to individual metals were found to be different from those due to mixture, underlining the importance of studying toxicants in combination. Research supported by department funding.