Introduction:
Contact herbicide diquat (DQ), redox cycling compound, mediates its systemic toxicity throughout the enlarged production of free radicals. Target organs are liver and kidney in humans. To-date, the mechanism of DQ-induced neurotoxicity has not been rationalized.

Objective:
The objectives of the study were to examine the ability of DQ to induce oxidative stress (OS) and/or nitrosative stress (NS) upon intrastriatal (i.s.) administration and to investigate the role of nitric oxide (NO_x) using NG-nitro-L-arginine methyl ester (L-NAME), a non-selective inhibitor of nitric oxide synthase (NOS) in the pretreatment of DQ i.s. administration.

Material and Methods:
The experiment was conducted on Wistar rats, randomly divided in experimental groups, receiving different treatments i.s. applied. Parameters of OS/NS such as: superoxide anion radical (O₂• ˉ), superoxide dismutase (SOD), malondialdehyde (MDA) and nitrates (NO₃ˉ) were measured in the cortex (bilaterally), at 30^th min, 24 hours and 7 days after the treatments.

Results:
Lethargy and high mortality rate were observed only in the DQ group (within 24 hours and 2-3 hours, respectively) after awakening from anesthesia. Markedly increased production of NO_x and O₂• ˉ along with elevated lipid peroxidation altogether contributed to DQ neurotoxicity. The most importantly, the L-NAME i.s. pretreatment protected treated animals from dying and diminished OS/NS response against DQ-induced neurotoxicity.

Conclusions:
The i.s. pretreatment with L-NAME resulted in neuroprotection against DQ neurotoxity, based on animal survival and reduced LPO in the cortex.