Neurotoxicity of thallium: biochemical and morphological study of organic lesions

A biochemical study of experimental thallium intoxication in newborn rats and its morphological consequences upon the brain of developing animals was undertaken. The thallium content was analyzed in the following encephalic regions: hippocampus, hypothalamus, mesencephalon, cerebellum, and cortex. One day after application of the toxic substance, a homogeneous distribution of the metal in the brain was found. Thallium concentrations in the mentioned regions were twice as high as those found in an adult rat, at the same dosage, 20 newborn Wistar rats were used for the histopathological study. 5 remained as witnesses, the rest received a single injection of thallium of .07 ml. of a solution with a concentration of .32 mg/Kg. 3 rats were sacrificed at 24, 48 and 72 hours; 3 at 7 days and 3 at 51 days. The brain , sciatic and crural nerves were fixated in 10% formaldehyde for 15 days. Cuts in paraffin and frozen sections measuring between 5 and 7 microns were taken from the fragments of different areas. These were stained with aniline methods (Masson, Gallego and H-E) and silver-gold impregnation as modified by Río-Hortega.