Chronic Administration with Rotenone does not Enhance MPTP Neurotoxicity in C57BL/6 Mice

Paraquat- and rotenone-induced models of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder mainly characterized by a loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. In recent years, several new genes and environmental factors have been implicated in PD, and their impact on DA neuronal cell death is slowly emerging. However, PD etiology remains unknown, whereas its pathogenesis begins to be clarified as a multifactorial cascade of deleterious factors. Recent epidemiological studies have linked exposure to environmental agents, including pesticides, with an increased risk of developing the disease. As a result, over the last two decades the "environmental hypothesis" of PD has gained considerable interest. This speculates that agricultural chemicals in the environment, by producing selective dopaminergic cell death, can contribute to the development of the disease. However, a causal role for pesticides in the etiology of PD has yet to be definitively established. Importantly, most insights into PD pathogenesis came from investigations performed in experimental models of PD, especially those produced by neurotoxins. This review presents data obtained in our laboratories along with current views on the neurotoxic actions induced by the two most popular parkinsonian pesticide neurotoxins, namely paraquat and rotenone. Although confined to these two chemicals, mechanistic studies underlying dopaminergic cell death are of the utmost importance to identify new drug targets for the treatment of PD.

Role of inducible or neuronal nitric oxide synthase in neurogenesis of the dentate gyrus in aged mice

We evaluated mainly the iNOS (inducible nitric oxide synthase) and nNOS (neuronal NOS) expression in the subgranular zone (SGZ) of the dentate gyrus of the hippocampus in young adult (8-week-old) and aged (60-week-old) mice. The present study demonstrates that the expression of nNOS was more pronounced than that of iNOS expression in the dentate gyrus of aged mice. Our study also suggests that aged mice exhibited a significant loss of motor activity as compared with young adult animals. Furthermore, our results provide that no significant change in the number of Neu N (Neuronal nuclei)-immunopositive neurons and GFAP (glial fibrillary acidic protein)-immunopositive astrocytes was observed in the dentate gyrus between young adult and aged mice. In contrast, a significant change in the number of Iba 1(ionized calcium-binding adaptor molecule 1)-immunopositive microglia in aged mice was observed in the dentate gyrus as compared to young adult animals. These results provide the novel evidence showing that the expression of nNOS may be crucial for the role of neurogenesis of the SGZ of the dentate gyrus in aged mice. Furthermore, our present findings demonstrate that the inhibition of nNOS expression in the SGZ of the dentate gyrus during aging processes may offer novel therapeutic strategies for anti-aging in humans.