SUBACUTE PB EXPOSURE DURING DEVELOPMENT AND UNBAITED TUNNEL MAZE PERFORMANCE IN MICE

Although research has linked chronic, low-level Pb exposure to behavio ral and cognitive changes in humans and animals, far less is known abo ut the effects of transient, subchronic Pb exposure during early postn atal development. The need to understand such effects is underscored b y the possibility that subchronic Pb exposure may not produce chronica lly elevated blood-Pb levels, but may produce long-term behavioral cha nges. To test this hypothesis, we investigated the effect of low-level Pb exposure on unbaited tunnel maze performance in Binghamton Heterog eneous Stock mice. Mice were either nontreated or given subchronic sod ium acetate, 5, 10, or 25 mg/kg Pb acetate intragastrically on postnat al (PN) days 6, 9, 12, 15, and 18. No further Pb exposures were given after postnatal day 18. Blood-Pb measurements were taken from selected mice on PN 18, 19, 23, 28, and 38. On PN 38-42, all mice were individ ually tested in an unbaited tunnel maze under nondeprived conditions. Locomotor activity, exploration, and experience-dependent changes in c ul-de-sac entries were recorded. Although Pb did not affect bodyweight and blood-Pb levels were below 10 mu g/dl at the time of behavioral t esting, a history of low-lever preweaning Pb exposure caused a dose-de pendent increase in cul-de-sac entries. This behavioral change was dis sociable from changes in bodyweight, degree of exploration or an a pri ori bias to enter cul-de-sacs. The current results support the hypothe sis that brief, subchronic Pb exposure during development produces beh avioral changes that last well beyond the exposure period, even when b lood-Pb declines to within ''acceptable'' levels (10 mu g/dl). (C) 199 8 Elsevier Science Inc.