Cadmium exposure in infancy: effects on activity and social behaviors of juvenile rats

In two experiments male and female infant rats were given single injections of cadmium chloride (0, 1, 2, 3 or 4 mg Cd/kg) on Day 5 or 6. Animals receiving the 3 and 4 mg/kg doses had high mortality rates at weaning; survivors were extremely underweight and were not used in postweaning tests. Male subjects receiving 2 mg/kg in infancy were significantly more active after weaning than littermates who had received 0 or 1 mg/kg doses, and on Day 29 they also engaged in significantly more rough and tumble play with a nontreated partner than did rats in the other groups. This effect of early cadmium exposure was also evident when males were tested with similarly treated subjects on Day 44: rats in the 2 mg/kg group had higher pinning frequencies than rats in the 0 or 1 mg/kg groups. In contrast, females in the 1 and 2 mg/kg groups did not have increased activity or rough and tumble play fighting. These data are consistent with the few correlational studies in human children which suggest changes in social behaviors associated with elevated tissue cadmium levels.