Neurotoxic Effects Induced by Intracerebral and Systemic Injection of Paraquat in Rats

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Abstract
1 The neurotoxic effects elicited by paraquat after systemic and intracerebral injection were studied in rats.2 Intrahippocampal microinfusion of paraquat (0.1 μmol) produced behavioural stimulation and electrocortical (ECoG) excitation followed, at 24 h, by multifocal brain damage. Similarly, microinfusion of paraquat (0.2-0.4 μmol) into the locus coeruleus, substantia nigra or into the raphe nuclei, where noradrenergic, dopaminergic and serotonergic neurons are present, respectively, elicited potent excitotoxic effects (n=6 rats per dose and area). A lower dose (0.01 μmol) of the herbicide or injection of the vehicle (1.0 μl) did not produce any behavioural, ECoG or neurodegenerative effect.3 After systemic administration, paraquat (20 mg kg-1s.c.) evoked limbic motor seizures and ECoG epileptogenic discharges; in 10 out of 15 treated rats neuronal cell death was observed in the pyriform cortex, but not in other brain regions. A dose of 5 mg kg-1was ineffective.4 Among the regions of the brain studied, high concentrations of paraquat were detected in the pyriform cortex 24 h after systemic administration (5.0 and 20 mg kg-1s.c.) lower levels being observed in the caudate nucleus.5 In conclusion, paraquat, given systemically or intracerebrally in rats produces neurodegenerative effects.