Differential effects of lead and zinc on inhibitory avoidance learning in mice.
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.
de Oliveira
F S
FS
Departamento de Fisiologia, Universidade Federal de Sergipe, São Cristóvão, SE, Brasil.
Viana
M R
MR
Antoniolli
A R
AR
Marchioro
M
M
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D005260:Female; D007854:Lead / Q000633:toxicity*; D008297:Male; D051379:Mice; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012153:Retention, Psychology / Q000187:drug effects*; D015032:Zinc / Q000633:toxicity*; D019345:Zinc Acetate / Q000633:toxicity*
D007854:Lead; D019345:Zinc Acetate; D015032:Zinc