Effects of lead in the laboratory mouse. Development and social behaviour after lifelong exposure to 12 microM lead in drinking fluid.

The effects of chronic exposure to 12 microM lead, from conception onwards, on development and social behaviour were investigated in the laboratory mouse. Lead was administered as 0.25% solution of lead acetate in the drinking fluid. This level of exposure did not affect reproductive success, but caused decreased birthweight and retarded early development in offspring of treated dams. Mortality prior to weaning was significantly greater in pups treated with lead, and animals treated with lead had significantly reduced body weights throughout their lives. Levels of lead in tissues were greatly increased in all treated animals, with females showing significantly higher levels than males. Behaviour was assessed by ethological methods in paired encounters between unfamiliar animals in a novel environment. At age 3-4 weeks Exploratory Behaviour and Social Investigation were significantly increased and Immobility was significantly decreased in animals of both sexes treated with lead. Social Investigation was also increased at age 7-8 weeks but Exploratory Behaviour was decreased. At age 15-16 weeks Non-Social Activity was increased in males and decreased in females, although Social and Sexual Investigation was not affected in these male-female encounters. Lead-treated males, aged 17-18 weeks, showed significantly shorter latencies to aggression towards unfamiliar males than did controls.