Abstract

DE OLIVEIRA, F.S.; VIANA, M.R.; ANTONIOLLI, A.R.  and  MARCHIORO, M.. Differential effects of lead and zinc on inhibitory avoidance learning in mice. Braz J Med Biol Res [online]. 2001, vol.34, n.1, pp. 117-120. ISSN 1414-431X.  http://dx.doi.org/10.1590/S0100-879X2001000100014.

We studied the effects of chronic intoxication with the heavy metals lead (Pb²⁺) and zinc (Zn²⁺) on memory formation in mice. Animals were intoxicated through drinking water during the pre- and postnatal periods and then tested in the step-through inhibitory avoidance memory task. Chronic postnatal intoxication with Pb²⁺ did not change the step-through latency values recorded during the 4 weeks of the test (ANOVA, P>0.05). In contrast, mice intoxicated during the prenatal period showed significantly reduced latency values when compared to the control group (day 1: q = 4.62, P<0.05; day 7: q = 4.42, P<0.05; day 14: q = 5.65, P<0.05; day 21: q = 3.96, P<0.05, and day 28: q = 6.09, P<0.05). Although chronic postnatal intoxication with Zn²⁺ did not alter a memory retention test performed 24 h after training, we noticed a gradual decrease in latency at subsequent 4-week intervals (F = 3.07, P<0.05), an effect that was not observed in the control or in the Pb²⁺-treated groups. These results suggest an impairment of memory formation by Pb²⁺ when the animals are exposed during the critical period of neurogenesis, while Zn²⁺ appears to facilitate learning extinction.

Keywords : lead; zinc; inhibitory avoidance; memory.