Toxicity of solvents exposure on the neuroendocrine system in rats : Role of amino acids supplementation

The goal of this study was to elucidate the neurotoxic effects of repeated exposure to gasoline, perchloroethylene or toluene on male rats, in addition to evaluate the interventive role of certain nutraceuticals against the neurodegenerative insult produced by inhalants abuse. The experimental groups were assigned as follows: Gp(1) control; Gp (2) exposed to gasoline vapors (3200 ppm) for quarter an hour/day; Gp(3) exposed to vapors of gasoline and treated orally with tyrosine (400 mg/kg b.wt.) with subsequent intraperitoneal injection with tryptophan (400 mg/Kg b.wt.); Gp(4) exposed to perchloroethylene vapors (800 ppm) for quarter an hour/day; Gp(5) exposed to vapors of perchloroethylene and treated with tyrosine and tryptophan; Gp(6) exposed to toluene vapors (1000 ppm) for quater an hour/day; Gp(7) exposed to vapors of toluene and treated with tyrosine and tryptophan. The experiment was extended for 45 days. Brain lipid peroxidation, reduced glutathione, serotonin, dopamine and GABA were determined, plasma testosterone, DHEA-S, T 3 and T 4 were determined. In addition to the histopathological investigations which were carried out. The results demonstrated that inhalation of gasoline, perchloroethylene or toluene caused elevation of brain lipid peroxidation, GABA and plasma DHEA-S levels. However, these inhalants induced depletion of brain glutathione, serotonin, dopamine as well as plasma testosterone, total triiodothyronine (T 3 ) and total thyroxin (T 4 ) levels. Histopathological alterations in the brain of the rats exposed to inhalants were also observed. On the other hand, marked improvement was detected on the treatment of exposed rats with tyrosine and tryptophan. Tyrosine and tryptophan supplementation exerted a modulatory effect on the most of biochemical parameters. Histopathological investigation of the brain revealed that the treatment of rats with tyrosine and tryptophan produced pronounced modulatory effect as indicated by the appearance of healthy neurons. In conclusion, the current study clearly indicated the serious effect of inhalants on the central nervous system of rats and the neuroprotective effect of tyrosine and tryptophan against inhalant neurotoxicity. [Report and Opinion. 2009;1(4):66-83]. (ISSN: 1553-9873).