ABSTRACT

Endosulfan is an organochlorine pesticide commonly used to control pests in vegetables,

cotton, fruits and other agricultural produce. It is a contact and stomach insecticide toxic to

mammals, fish and other aquatic organisms. Several reports have shown that it is a highly

neurotoxic agent. The aim of this study was to evaluate the role of brain lipoperoxidation

and oxidative stress in sensorimotor and cognitive changes, arising from endosulfan

exposure in Wistar rats and the ameliorative potentials of vitamin E. Thirty two (32) male

Wistar rats were randomly divided into four groups of eight (8) rats each: group I rats

received soya oil at 2 ml/kg body weight; group II rats received vitamin E at a dose of 30

mg/kg body weight; group III rats received endosulfan at a dose of 12 mg/kg; and group IV

rats received vitamin E (30 mg/kg) followed by endosulfan (12 mg/kg) after 30 mins. The

regimens were administered orally by gavage once daily for 28 days. The rats were

examined for neurobehavioural parameters: assessing motor endurance and neuromuscular

coordination at weeks 0, 2 and 4; and for cognition 48 hrs to the termination of the study.

At the end of the study period, the rats were euthanized. Brain homogenate samples were

evaluated for malondialdehyde (MDA) concentration and activities of superoxide

dismutase (SOD) and catalase (CAT). The results showed significant elevation (p < 0.05) in

MDA concentration in the endosulfan-treated group compared to the vitamin E pre-treated

group; a significant increase in CAT activity in the endosulfan-treated group (p < 0.05)

compared to the control group, and no significant change in SOD activity in all the groups.

Endosulfan-treated rats    showed decreased   motor endurance and    neuromuscular

coordination, compared to that of the control rats and rats in other treatment groups;

although the difference was not significant (p > 0.05). No significant difference (p > 0.05)

was recorded for the learning acquisition in all treatment groups, although rats in the

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CHAPTER ONE

1.0 INTRODUCTION

1.1 Background

The subtle impact of chemicals in our environment upon animals was first highlighted by

Rachel Carson with her work on Dichlorodiphenyltrichloroethane (DDT) in the 1950s and

1960s. More recently, studies have shown clearly the impact of man-made chemicals and

many pesticides. These may interfere with or disrupt normal body functions, exacerbating

the development of cancers, reducing sperm counts, interfering with normal development,

among other health impacts (Colborn et al., 1996). In recent years, there has been a

tremendous increase in the use of these chemicals without paying much attention to the

adverse effects they may have due to the toxic ingredients (Yekeen and Adeboye, 2013).

Pesticide-related adverse effects in humans, animals and birds remain a serious public

health concern (Farag et al., 2014). Pesticides are a group of chemicals made for the

purpose of killing or otherwise deterring “pest” species. The word pesticide may refer to

insecticides, herbicides, fungicides, or other pest control formulations. Pesticides are known

to be the most important tool for the production of adequate food supply for an increasing

world population and for the control of vector-borne diseases (Mahugija et al., 2017), they

are however, inherently toxic and often pose significant toxicological risks to a myriad of

non-target organisms (US EPA, 2009; Ondarza et al., 2014). Pesticides applied to crops

and livestock can remain on or in our food (Colborn et al., 1996; Mahugija et al., 2017),

finally finding their way to the food chain threatening the ecological balance and the

biodiversity of nature (Konstantinou et al., 2006). Most of the chemicals which are used as

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