Chronic lead and brain development: Intraocular brain grafts as a method to reveal regional and temporal effects in the central nervous system

Abstract

A model is presented for selective studies of regional and temporal effects of chronic lead exposure on brain development, based on intraocular brain tissue grafting. Adult rat recipients were given lead acetate (1–2%) in their drinking water. Controls received sodium acetate in the drinking water or tap water. One week later, developing brain tissues obtained prenatally from different regions of the central nervous system were homologously grafted to the anterior chamber of the eye. Survival, vascularization, and growth were followed in oculo by repeated measurements of graft size. Growth curves were thus obtained for grafts from isolated selected brain areas, grafted at different stages of development to recipients on different concentrations of lead. Lead treatment (1%) caused a significant and pronounced delay of growth of the substantia nigra area during the second and third week postgrafting, approximately corresponding to the first 2 weeks after birth. Grafts of the hippocampal formation showed a slight impairment of growth following lead treatment while there were no detectable effects on size of cerebellar grafts. Grafts of the developing parietal cerebral cortex were inhibited in their growth in host animals given 2% lead while there was a small but significant increase in size following 1% lead. These results demonstrate the applicability of the grafting technique for studies of chronic low level lead intoxication. The method has revealed highly significant effects of lead on growth of certain selected brain areas and will be used for further histological, biochemical, and electrophysiological analysis of chronic lead effects on development of defined brain areas.