Alzheimer’s- and Multiple Sclerosis-Like Features on Key Brain Centres of Wistar Rats Exposed to Cypermethrin and Dichlorvos

Abstract

Insecticides are suspected environmental factors in the aetiology of Alzheimer’s and multiple sclerosis diseases. Several studies have reported long-term exposure to insecticides in the development of plaques, neurofibrillary tangles, and demyelination. However, there is no literature on the impact of short-term combined insecticide exposure on specific neurological conditions. This investigation assessed the role of short-term exposure to the mixture of cypermethrin and dichlorvos on Alzheimer’s- and multiple sclerosis-like features. Thirty-two male adult Wistar rats were divided into four groups: the control group was exposed to normal atmospheric air, and the test groups were exposed to a combined cypermethrin and dichlorvos at 2, 3, and 4 h/day [LC50 of 5 mm-1 (4.4 ppm) of dichlorvos and 10 mm-1 (8.7 ppm) of cypermethrin] for four weeks. In the last three days of exposure, neurobehavioural tests were conducted. Twenty-four hours after the last exposure, the animals were anesthetized using chloroform vapour. The brains were harvested by making an occipitofrontal incision for biochemical and histological assessment. The fixation was done in 10% neutral buffered formalin for 48 h following the brain mapping to isolate the brain tissue of interest. The insecticide-exposed rats showed significant (p<=0.05) progressive behavioural deficits and oxidative stress when compared to the control group. Neurofibrillary tangles, senile plaques, and demyelination of the neurons were observed in the brains of the insecticide-exposed rats. This study indicates that the mixture of cypermethrin and dichlorvos can induce the development of Alzheimer’s and multiple sclerosis within a short time