Neurotoxicity risk of repeated exposure to inhalants: potential role of melatonin and vitamin B as neuron protectors

ABSTRACT

The main objective of the current study was to elucidate the neurotoxic effects induced by repeated exposure to gasoline, perchloroethylene or toluene on male rats. The study was extended to evaluate the interventive role of melatonin, folic acid and vitamin B12 against the neurodegenerative insult produced by inhalants abuse. Ten experimental groups were assigned as follows group [1] control group; group[2] The rats were exposed to gasoline vapors [3200 ppm] for quarter an hour / day; group [3] The rats were exposed to gasoline vapors then treated with melatonin [10 mg / kg b. wt]; group [4] The rats were exposed to gasoline vapors then treated with folic acid [200 mg / kg b. wt] and vitamin B12 [o.o4 mg / kg b.wt]; group [5] The rats were exposed to perchloroethylene vapors [800 ppm] for quarter an hour/day; group [6] The rats were exposed to perchloroethylene vapors then treated with melatonin; group [7] The rats were exposed to perchloroethylene vapors then treated with folic acid and vitamin B12; group [8]. The rats were exposed to toluene vapors [1000 ppm] for quater an hour / day; group [9] The rats were exposed to toluene vapors then treated with melatonin and group [10] The rats were exposed to toluene vapors then treated with folic acid and vitamin B12. The experiment was extended for 45 days. Brain lipid peroxidation, reduced glutathione, serotonin, dopamine, and GABA were measured. In addition, plasma total testosterone and DHEA-S were determined. Histopathological investigation of the brain tissue was also carried out. The results demonstrated that inhalation of gasoline, perchloroethylene, or toluene causes elevation of brain lipid peroxidation, GABA and plasma DHEA-S levels. However, these inhalants induced depletion of brain reduced glutathione, serotonin, dopamine as well as plasma total testosterone levels. Histopathological alterations in the brain of the rats exposed to inhalants were also observed. On the other hand, marked improvement was detected on treatment of the exposed rats with either melatonin or folic acid and vitamin B12. Melatonin supplementation exerted a better modulatory effect on the most of the measured parameters in rats exposed to gasoline than rats exposed to gasoline and treated with folic acid and vitamin B12. Rats exposed to perchloroethylene or toluene then treated with folic acid and vitamin B12 revealed more pronounced improvement in the most of biochemical parameters than that detected by melatonin treatment. Histopathological investigation of the brain revealed that the treatment of rats exposed to gasoline with melatonin produced more pronounced modulatory effect than that in case of treatment with folic acid and vitamin B12 as indicated by the appearance of healthy neurons and astrocytes. However, treatment with folic acid and vitamin B12 to rats exposed to perchloroethylene showed more curative effect than that in case of treatment with melatonin as indicated by observing the neurons more or less like control. Also, the treatment with folic acid and vitamin B12 to rats exposed to toluene showed better effect than that in case of treatment with melatonin as indicated by the appearance of the neurons as much as control, except of few neurons that appeared with some degree of degeneration. The current results clearly indicated the serious effect of inhalants on the central nervous system of rats. Treatment with melatonin or vitamin B was found to have a modulatory action against inhalant neurotoxicity