As little is known about the neurotoxicity of the histological structure of the brain, this study focuses on the histological side of four- to six-month-old adult Wistar rat brains, which were examined after 0.1 mg\g organophosphate had been administered orally. In this study, the lesions were mainly localized at the hippocampus and substantia nigra (compacta pars) region. Distinct areas of necrotic and apoptotic tissues were detected in the CA1, CA2, and dentate gyrus of the hippocampus and compacta pars of the substantia nigra. Programmed cell death in the dentate gyrus was observed as early as 72 hours after treatment and necrosis of some brain regions. Moreover, Lewy bodies were noticed in the compacta pars of the substantia nigra. The most important symptoms of parkinsonism were observed in the substantia nigra (compacta pars). These were decreased neurons, increased neuronal melanin in the neurons, and increased glial cells. The degeneration of some neurons was reported in the polymorphic and pyramidal layers. The data showed an increase in the density of the axon membrane and several changes to the axis structure, such as the disappearance of the myelin sheath in some areas along the axis.

This study aimed to detect the neurohistological damages of chronic exposure to low levels of pesticide (paraquat) in the hippocampus, and substantia nigra in Wistar rats' brains. The neurotoxic effects of acute poisoning are well established but the possibility that low level exposure causes different diseases is controversialIt is important to get a clear answer to this question as more individuals are at risk of low level exposure than acute poisoning. The anatomical and histological of current study to affected brains showed cells display the cytological changes of herbisecticides-lesioned brain tissue, such as a significant decrease in the size of the brain was observed, as most of its external features disappeared. in addition, we detected vacuolization around cells that degenerated because many reasons like apoptosis or necrosis, and the intracellular neurofibrillary tangles were observed at many regions such as the hippocampus and substantia nigra. Moreover extracellular amyloid plaques take fibers form were detected. we also observed degenerated in CA1, CA2 and CA3 regions (molecular layer, polymorphic layer and pyramidal layer) by pigmenting degenerated neurons with silver nitrate with increased astrocytes of glia cells.