Journal Article

Traumatic Brain Injury in Adult Rats Causes Progressive Nigrostriatal Dopaminergic Cell Loss and Enhanced Vulnerability to the Pesticide Paraquat

Mortazavi, Farzad, Hovda, David, Hutson, Che Brown, Lazo, Carlos R., Chesselet, Marie-Francoise, Giza, Christopher C.

2011

Overview

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of nigrostriatal dopaminergic neurons and the accumulation of alpha-synuclein. Both traumatic brain injury (TBI) and pesticides are risk factors for PD, but whether TBI causes nigrostriatal dopaminergic cell loss in experimental models and whether it acts synergistically with pesticides is unknown. We have examined the acute and long-term effects of TBI and exposure to low doses of the pesticide paraquat, separately and in combination, on nigrostriatal dopaminergic neurons in adult male rats. In an acute study, rats received moderate TBI by lateral fluid percussion (LFP) injury, were injected with saline or paraquat (10 mg/kg IP) 3 and 6 days after LFP, were sacrificed 5 days later, and their brains processed for immunohistochemistry. TBI alone increased microglial activation in the substantia nigra, and caused a 15% loss of dopaminergic neurons ipsilaterally. Paraquat increased the TBI effect, causing a 30% bilateral loss of dopaminergic neurons, reduced striatal tyrosine hydroxylase (TH) immunoreactivity more than TBI alone, and induced alpha-synuclein accumulation in the substantia nigra pars compacta. In a long-term study, rats received moderate LFP, were injected with saline or paraquat at 21 and 22 weeks post-injury, and were sacrificed 4 weeks later. At 26 weeks post injury, TBI alone induced a 30% bilateral loss of dopaminergic neurons that was not exacerbated by paraquat. These data suggest that TBI is sufficient to induce a progressive degeneration of nigrostriatal dopaminergic neurons. Furthermore, TBI and pesticide exposure, when occurring within a defined time frame, could combine to increase the PD risk.

• Publisher: SAGE Publications,Mary Ann Liebert, Inc
• Subject: Animals / Brain / Brain damage / Brain Injuries - metabolism / Brain Injuries - pathology / Cell Death - physiology / Corpus Striatum - drug effects / Corpus Striatum - metabolism / Corpus Striatum - pathology / Diagnosis / Dopamine - metabolism / Herbicides - pharmacology / Immunohistochemistry / Injuries / Male / Nerve Degeneration - metabolism / Nerve Degeneration - pathology / Neurons / Neurons - drug effects / Neurons - metabolism / Neurons - pathology / Original / Paraquat - pharmacology / Parkinson's disease / Pesticides / Rats / Rats, Sprague-Dawley / Risk factors / Rodents / Substantia Nigra - drug effects / Substantia Nigra - metabolism / Substantia Nigra - pathology / Tyrosine 3-Monooxygenase - metabolism