OBJECTIVETo investigate the effects of exposure of paraquat and maneb on the behavior, the morphology and electrical activity of the Substantia nigra and striatum, and to discuss the relationship between this two pesticides and Parkinson's disease.

METHODS37 rats were divided randomly into 3 groups: control group (n = 11), paraquat (10 mg/kg) group (n = 13) and combinative group of paraquat (10 mg/kg) and maneb (30 mg/kg) (n = 13), and were exposed twice a week for 6 weeks by intraperitoneal injection. The behavior of animals in the declined-plane, the vertical-grid and the open-field test were observed. The morphology of substantia nigral neurons were investigated by HE pathology. The spontaneous discharge of striatum neurons were recorded after exposure.

RESULTSCompared to the control group and the pre-exposure group, both the numbers of animals sliding down from the declined-plane and the latency of rats' moving on the vertical-grid significantly increased, and the animals' autonomic movement decreased significantly (P < 0.05, P < 0.001). After the combinative exposure, the neurons of the Substantial nigra pars compacta (SNPc) were progressively impaired, the cell density of the paraquat group [(82.17 ± 12.91) n/mm(2)] and the combined group [(41.15 ± 6.44) n/mm(2)] were lower than that in control group (143.10 ± 20.85 n/mm(2)] (P < 0.01). In the paraquat group (5.97 ± 7.30 Hz) and the combined group [(6.95 ± 9.87) Hz], the average discharge rates of the striatum neurons were increased significantly compared to the control group [(1.78 ± 5.05) Hz] (P < 0.01). The bursting discharge was increased significantly in the combined group (22.3%) compared to the control group (9.8%) and the paraquat group (5.6%) (P < 0.05, P < 0.01).

CONCLUSIONThe co-exposure of paraquat and maneb could induce similar symptoms to Parkinsonism syndrome of rats such as rigidity, moving reduction and etc, and the combined exposure had a certain enhanced effect compared to alone paraquat exposure. The combinative exposure of paraquat and maneb could cause neural loss in SNPc and it is involved with the enhanced electrophysiological activity in striatum. The synergy toxicity of paraquat and maneb in nigrostriatal system is related to Parkinson's disease.