Effect of Toluene, An Environmental Toxin in CNS Function of Experimental Animals

Abstract

BACKGROUND AND OBJECTIVES Neurodegeneration is the progressive loss of structure or function of neurons, including death of neurons. Many neurodegenerative diseases including amyotrophic lateral sclerosis, Parkinson’s, Alzheimer's, and Huntington's occur as a result of neurodegenerative processes due to exposure to various environmental toxins. Environmental pollutants have emerged as a key area of research to focus on to study neurodegeneration. Exposure to environmental neurotoxins can cause permanent, untreatable brain damage and results in reduced IQ scores and disruption in behavior. Toluene is a member of the volatile organic compound (VOC) family and an environmental toxin which has high prevalence in the atmosphere which continues to pose a significant health problem in industrial nations. Toluene was selected because of it has reported behavioral and neurophysiological effects in both humans and animals. The objective of this study is to evaluate the effects of toluene on the brain using rats. MATERIALS AND METHODS In present protocol after acclimatization and training, animals were divided in five groups as Normal control (NC), Sham control (SC), Toluene low dose (2 mg/kg, icv) treated (LD); Toluene medium dose (4 mg/kg, icv) treated (MD); and Toluene high dose (6 mg/kg, icv) treated (HD) groups. Rats were anesthetized with 5 mg/kg diazepam and 60 mg/kg ketamine and toluene (not more than 10 micro litre once) was administered by intracerebroventricular (ICV) route in rat brain with the help of stereotaxic device in LD, MD and HD group animals. Sham control (SC) group animals have not been induced with the investigative agent. The behavior parameter readings were collected across three time scales which included Preinduction i.e. before administration of toluene and on the 15th day and 35th day Post induction i.e. after administration of toluene. The Y-Maze, Actophotometer and Tail suspension test were utilized for evaluation of the neurobehavioral parameters. After completion of the 35th day Post induction of toluene the animals were sacrificed and the brains were collected. The brains were then utilized to evaluate various oxidative stress parameters and neurotransmitter estimation parameters. Apart from this the rat brains were used for performing brain histo patholgical studies and the damage on the brain samples was evaluated