Effects of 1.2 microM lead in the laboratory mouse: developmental and behavioural consequences of chronic treatment

Lead acetate, as a 0.025% (1.2 microM) solution in the drinking fluid, did not adversely affect the reproductive success in breeding mice, weights of pups at birth or cause delays in development. At 21 days, the treated offspring showed reduced weights but these returned to normal values in adulthood. Offspring of treated mice were given 1.2 microM lead acetate as drinking fluid after weaning. The mean daily intake of lead amounted to 2.4 and 2.6 mg/100 g body wt in females and males respectively and caused significant increases in the concentrations of lead in bone and brain. Sequestration of bone was greater in females than males. The behaviour of the offspring was examined by ethological analysis of social encounters between pairs of unfamiliar mice of similar treatment groups in a neutral cage. Evidence of enhanced reactivity to the test situation was seen in treated males at age 3-4 weeks by increased social investigation during the first 3 min of the 20 min encounter, at 7-8 weeks by decreased immobility in the final 5 min of the test and at 18-19 weeks by an increased duration of exploratory behaviour. However, when encountering females at 30-31 weeks, the treated males showed more immobility than did the controls. Treated females at 3-4 weeks, in the first 3 min of the test, showed a decreased frequency of exploratory behaviour and increased immobility, but at 7-8 and 18-19 weeks they showed enhancement of social and sexual investigation. Behaviour was unaltered at 30-31 weeks in encounters with unfamiliar males.(ABSTRACT TRUNCATED AT 250 WORDS)