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Regulatory developmental neurotoxicity testing: a model study focussing on conventional neuropathology endpoints and other perspectives.

de Groot DMG; Bos-Kuijpers MHM; Kaufmann WSH; Lammers JHCM; O'Callaghan JP; Pakkenberg B; Pelgrim MTM; Waalkens-Berendsen IDH; Waanders MM; Gundersen HJJ
Environ Toxicol Pharmacol 2005 May; 19(3):745-755
Our aim was to investigate a model of the morphologic approach proposed in guidelines for developmental neurotoxicity testing (DNT). Hereto, a limited DNT study [EPA Health Effects Test Guidelines OPPTS 870.6300, 1996a. Developmental Neurotoxicity Study "Public Draft", United States Environmental Protection Agency; Prevention, Pesticides and Toxic Substances (7101); EPA 712-C-96-239, June 1996] was carried out with different doses of methylazoxy methanol acetate (MAM), known to affect brain morphology and neuron numbers in the developing brain. After gross examination, the brains of F1-animals were further dissected along neuro-anatomical landmarks to ensure homology between tissues of different individuals. The (relative) weight of the brain (parts) was determined. One brain half (alternating left/right to avoid lateralization) was further used for microscopic slide reading and measurement of brain layer width (linear morphometry); the other was set aside for stereologic investigation in a later phase of the study. In the offspring, a clear reduction in brain size (gross macroscopy) and weight (MAM high- and top-dose groups) was observed on postnatal days (PN) 22 and 62, but this reduction was hard to pinpoint in the microscope as the changes primarily appeared quantitative in nature, rather than qualitative. Linear measurements of brain layer width appeared very sensitive and efficient. This first step of a project is presented and the perspectives of a further stereologic investigation are discussed.
Neurotoxicity; Neurotoxic-effects; Neurotoxicology; Neurotoxins; Models; Neuropathology; Microscopy; Microscopic-analysis; Animals; Animal-studies; Author Keywords: Rat; Methylazoxy methanol acetate (MAM); Regulatory developmental neurotoxicity (DNT) testing (Guidelines OPPTS 870.6300, EPA; OPPTS 870.8600, EPA; OECD 426); Neuropathology endpoints; Microscopy and linear morphometry; Neuron numbers and stereology
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Environmental Toxicology and Pharmacology
Page last reviewed: May 11, 2023
Content source: National Institute for Occupational Safety and Health Education and Information Division