Effects of lead in the laboratory mouse--2. Development and social behaviour after lifelong administration of a small dose of lead acetate in drinking fluid.

Administration of 0.13% lead acetate solution as drinking fluid to breeding mice was without significant effect on the numbers of live or dead births or on weight of pups at 1 day. The appearance of fur was delayed and the body weights at 21 days and 31-38 weeks were smaller than in controls. On weaning, the treated offspring received 0.13% lead acetate as drinking fluid. Concentrations of lead in bone and brain were markedly raised above control levels at 18 and 34 weeks, being greatest at 34 weeks. There were no significant sex differences. The behaviour of the treated offspring in social encounters was shown by ethological procedures to differ from that of controls. The most consistent change after treatment with lead was enhancement of social and sexual investigation. This was seen in females at 26-27 weeks when encountering male partners, in isolated males at 32-33 weeks encountering male partners and in group-housed males and females in single sex encounters at 17-18 weeks. At 17-18 weeks, the duration of this behaviour was increased in treated females in the first 3 min and in treated males in the final 5 min of the 20 min period of observation. Behavioural changes in juvenile mice at 6--7 weeks occurred only during the final 5 of the 20 min observation. At 3--4 weeks only a marginal difference in behaviour was detectable, this being in the treated females. Overall the behavioural effects of lead differed between males and females and were different in juveniles from those seen in adulthood.