RT Journal Article
SR Electronic
T1 The Nigrostriatal Dopaminergic System as a Preferential Target of Repeated Exposures to Combined Paraquat and Maneb: Implications for Parkinson's Disease
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 9207
OP 9214
DO 10.1523/JNEUROSCI.20-24-09207.2000
VO 20
IS 24
A1 Mona Thiruchelvam
A1 Eric K. Richfield
A1 Raymond B. Baggs
A1 Arnold W. Tank
A1 Deborah A. Cory-Slechta
YR 2000
UL http://www.jneurosci.org/content/20/24/9207.abstract
AB Experimental evidence supporting 1,1′-dimethyl-4,4′-bipyridinium [paraquat (PQ)] as a risk factor for Parkinson's disease (PD) is equivocal. Other agricultural chemicals, including dithiocarbamate fungicides such as manganese ethylenebisdithiocarbamate [maneb (MB)], are widely used in the same geographical regions as paraquat and also impact dopamine systems, suggesting that mixtures may be more relevant etiological models. This study therefore proposed that combined PQ and MB exposures would produce greater effects on dopamine (DA) systems than would either compound administered alone. Male C57BL/6 mice were treated twice a week for 6 weeks with intraperitoneal saline, 10 mg/kg paraquat, 30 mg/kg maneb, or their combination (PQ + MB). MB, but not PQ, reduced motor activity immediately after treatment, and this effect was potentiated by combined PQ + MB treatment. As treatments progressed, only the combined PQ + MB group evidenced a failure of motor activity levels to recover within 24 hr. Striatal DA and dihydroxyphenylacetic acid increased 1–3 d and decreased 7 d after injections. Only PQ + MB reduced tyrosine hydroxylase (TH) and DA transporter immunoreactivity and did so in dorsal striatum but not nucleus accumbens. Correspondingly, striatal TH protein levels were decreased only by combined PQ + MB 5 d after injection. Reactive gliosis occurred only in response to combined PQ + MB in dorsal–medial but not ventral striatum. TH immunoreactivity and cell counts were reduced only by PQ + MB and in the substantia nigra but not ventral tegmental area. These synergistic effects of combined PQ + MB, preferentially expressed in the nigrostriatal DA system, suggest that such mixtures could play a role in the etiology of PD.