HOME CAGE BEHAVIOR AND LEAD TREATMENT IN RHESUS-MONKEYS - A COMPARISON WITH OPEN-FIELD BEHAVIOR

Nursery-reared rhesus monkeys were treated with no (n = 4) or moderate levels of lead (n = 4) during the first postnatal year. Mean blood le ad levels peaked at 55 mug/dl at 5 weeks of age, averaged 36 mug/dl fo r the remainder of the first year postpartum, and declined to less-tha n-or-equal-to 5 mug/dl for the 4 monkeys by 2.3 years of age. Previous ly, the lead-treated monkeys exhibited increased environmental explora tion and decreased inactivity in a nonhuman primate version of the ope n field when tested at 4, 5, and 6 years of age (5,6). The current stu dy was designed to assess behavior in the home cage of these monkeys a t 6 years of age to determine: (a) whether the increased exploration w as specific to the open field, and (b) any lead-related behavioral alt erations specific to the home cage. Each monkey was observed twice wee kly for 10 weeks and the duration and frequency of 17 behaviors were r ecorded. Lead treatment did not result in significant alterations in a ny of the six behaviors which occurred with enough frequency to warran t analysis. As a whole, all monkeys were either inactive or engaged in self-grooming for a large proportion of the test session. Less freque nt were behaviors such as locomotion, environmental exploration, and s elf-directed behaviors. The distribution of behavioral activities in t he home cage differed from that in the open field. Potential reasons f or the expression of significant lead-related effects in the open fiel d and not in the home cage are discussed as well as the differences in distribution of behavioral activities.