THE IMPACT OF CYPERMETHRIN AND DICHLORVOS MIXTURE OF PYRETHROID INSECTICIDES ON THE MYELINATION OF SUBSTANTIA NIGRA OF ADULT WISTAR RATS

ABSTRACT Cypermethrin is a synthetic pyrethroid used as an insecticide on a large scale. It can be used in the control of wide range of insects, flies and other insects in animal houses, mosquitoes, cockroaches, houseflies and other pests in public health. It is used as an animal ectoparasite. In this study, we investigated the impact of cypermethrin and dichlorvos mixture of pyrethriod insecticide on myelination of substantia nigra of male wistar rat. Thirty-two (32) animals were used for this experiment, they were divided into four (4) groups of eight animals each. Group A served as the control group while group B, C & D served as experimental group. The animals were allowed for a period of two weeks for acclimatization followed by exposure to the cypermethrin and dichlorvos mixture via inhalation under a controlled room temperature of about 25-28°C, relative humidity of about 60-80% and photo-periodicity of 12h day / 12h night. group A (control) inhaled fresh air, groups B, C, and D were exposed to a mixture of 5mg/m3 (4.4 ppm) of dichlorvos and 10mg/m3 (8.7 ppm) of cypermethrin insecticide for 2hrs/day, 3hrs/day and 4hrs/day respectively. The animals were exposed for five days a week in four weeks. Wire suspension test was utilized to demonstrate the neuro-behavioural changes across the four groups of animals to identify the animal groups that have lost its motor function. Twenty-four hours after the last exposure following the neurobehavioral test, the animals were weighed, then anaesthetized under chloroform vapor and the animal skull dissected by occipito-frontal incision. The brain tissues were harvested from the cranial vault, some of the tissues were prepared for biochemical analysis through the process of homogenization while the remaining tissues were fixed in 10% Neutral Buffered Formalin for 48hrs and grossed to isolate the brain tissue of interest for immuno-histological investigations.There was significant loss of weight presented the experimental groups B,C and D when compared to the weight of the control group. The neurobehavioral test presents statistical non-significant decrease in the motor function of the exposed groups when compared to the control group (p