SUBLETHAL EXPOSURE TO LEAD INHIBITS ACQUISITION AND RETENTION OF DISCRIMINATE AVOIDANCE-LEARNING IN GREEN FROG (RANA-CLAMITANS) TADPOLES

Green frog, Rana clamitans, tadpoles were exposed to 750 μg Pb/L as lead nitrate. Tadpoles used in learning acquisition tests were exposed for 6 d (144 h) and tadpoles used in retention (memory) tests were exposed for 5 d (120 h). Both lead‐exposed and control tadpoles were conditioned, using shock avoidance, to associate illumination (conditioned stimulus) with shock (unconditioned stimulus). The mean response time, the number of avoidances and differences in the learning curves of the lead‐exposed and control tadpoles were compared statistically. Learning acquisition tests showed increased response times and fewer avoidances in lead‐exposed as compared to control tadpoles. Retention tests showed higher response times and no avoidances in lead‐exposed tadpoles as compared to controls. These results indicate that sublethal exposure to lead adversely affected both acquisition learning and memory. Copyright © 1990 SETAC