Histologic Features of Catecholaminergic Neurons in Substantia Nigra Pars Compacta Of Rat That Treated by Paraquat Dichloride for 12 Weeks

Abstract

Paraquat dichloride is a herbicide to eradication wild grass that has a putative risk factor for Parkinson disease, a disease due to disruption of dopamine production at substantia nigra pars compacta as a part of mesencephalon. The exact dosage of paraquat dichloride that capable to causing the histological changing of catecholaminergic neuron for long time exposure is not determined yet. The aim of the research was to find out histological features of catecholaminergic neurons in substantia nigra pars compacta  after treated by paraquat dichloride for 12 weeks. Sixty adult male rats were divided into 6 groups, 5 rats each. Group I (control) were injected by aquabidest. Group II – VI were injected respectively by paraquat dichloride 2.5; 5; 7.5; 10; and 12.5 mg/kg bw intraperitoneally, once a week for 12 weeks. A days after last injection, rats were sacrificed according to animal welfare, perfused intracardially in 10% buffered formalin. The brains were processed for histology in paraffin section. First section were histochemistry stained using cresyl violet and the next section were immunohistochemistry stained using tyrosine hydroxylase antibody as a marker of dopaminergic neurons. The results show that dopaminergic neurons in substantia nigra pars compacta are bipolar and multipolar in shape; at dosages 10-12.5 mg/kg bw were less intense of tyrosine hydroxylase immunoreactivity and the cell membrane were disintegrated.  In conclusion, the injection of paraquat dichloride at dosages 10 to 12,5 mg/kg bw once a week for 12 weeks caused degeneration of  dopaminergic neurons in substantia pars compacta of rat.