[Neurobehavioral and systemic effects in lead-exposed rats after an exposure-free interval of four months duration (author's transl)].

Abstract

This experiment was designed to study the degree of recovery from lead-induced neuro-behavioral deficit after normalization of blood lead-level (PbB). Female Wistar-rats were given a diet containing lead-acetate (2260 ppm Pb) for 60 d until mating, giving rise to a PbB-increase from 53 microgram/d1 (before mating) to 84 microgram/d1 (after weaning). Lead-exposure of their male offspring was continued for 4 months with their PbB levelling off at 40 microgram/d1 (table 1). Lead-feeding was discontinued thereafter for another 4 months, PbB declining to a final level of 12 microgram/d1 (table 1). These animals were then compared for neurobehavioral functions to age-matched controls with respect to discrimination-learning (Lashley jumping-stand) and motor activity (open field-test). In addition recovery from initial loss of body-weight after partial food-deprivation was measured, known to be retarded at elevated PbB. The results may be summarized as follows: Formerly Pb-treated animals subsequently raised on a lead-free diet resulting in PbB-normalization within 4 months as compared to untreated controls exhibit (1) significant retardation of recovery from initial loss of body-weight (fig 4), (2) significant increase of error-repetitions in discrimination-learning (table 4; fig. 5) indicating disturbances of learning-performance without a change in learning-speed, and (3) significant hypoactivity (ambulation) without a significant change of other variables of open field-behavior (table 5; fig. 6). These results demonstrate, that some neurobehavioral and systemic symptoms of Pb-related dysfunction persist even after normalization of PbB, thus indicating partial irreversibility of Pb-induced damage.