National Science Foundation Experimental Program to Stimulate Competitive Research Summer Undergraduate Diversity Research Program Sherry Farokhzad Faculty Advisor Dr. Diana Lurie, Department of Pharmaceutical Sciences Lead Exposure During Development Induces Neuronal Changes in the Murine Auditory Brain Stem Abstract

Lead is an important environmental toxin and is a factor for reading disorder and auditory processing disorders. The CDC reports that 930,000 children have blood-lead concentrations above the "safe" amount of 10 ug/dL. This study examined immunochemical changes in the primary auditory nucleus, anteroventral cochlear nucleus (AVCN) of three-week-old balb/c mice treated with low, medium, and high doses of lead acetate. Following lead exposure, brains were embedded in paraffin and sectioned at 10 microns. A 1 and 6 series of sections were immunostained for neurofilament (structural protein found in neurons). Sections were visualized using Avidin-Biotin horseradish Complex (ABC) / Diaminobenzidine Tetrahydrochloride (DAB) Immunocytochemistry (ICC). Untreated control AVCN has several darkly stained neurons and neurofilament staining is for the most part evenly distributed within axons, with the exception of a few neurofilament clusters. The low dose of lead results in loss of neurofilament staining in most neurons in AVCN. The medium dose of lead results in lightly stained neurons and the entire nucleus is lightly, yet evenly stained throughout compared to that of the low dose. The high dose of lead results in a few darkly stained neurons within the AVCN, with many unstained areas and contrasting dark clusters of neurofilament staining. These results suggest that murine AVCN shows loss of neurofilament immunostaining with low doses of lead and confirms previous studies within the avian auditory brainstem. Low doses of lead appear to be detrimental to the auditory system, and the current exposure standard of 10 ug /dL should be re-examined.