Bilaterl Substantia Nigra Pars Compacta-Lesioned as a Model for Memory Impairment of Parkinson's Disease in Rats

Long ago, only the movement disorder of Parkinson's disease (PD) was considered by researchers, but non-motor symptoms such as cognitive and memory disorder precedes the clinical symptoms. In the present study, a 6-hydroxydopamine (6-OHDA) rat memory impairment model of PD was used to investigate in vivo production of oxidative stress and memory disorder.

6-OHDA (6μg/2μl of saline) was bilaterally injected in the substantia nigra pars compacta (SNC). The sham-operated rats were injected with saline. Spatial memory was evaluated in morris water maze (MWM). 6 days after neurosurgery the rats were killed and hippocampal tissues were separated on an ice-cold surface. Analysis of superoxid dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) activity were performed.

There was no significant difference in total traveled distance between groups therefore, injured animals had no problem in movement. There was also a significant increase in the escape latency in lesioned group as compared to the sham (P<0.000). The time spent in quadrant target zone of injured rats was significantly shorter than sham rats (P<0.002). One way ANOVA analyses showed a significant reduction in SOD antioxidant activity in the hippocampus of injured rats as compared to sham (P<0.05). Moreover this reduction was not significant in GPX and CAT enzymes.

Bilaterl substantia nigra pars compacta-lesioned as a model in early phase of Parkinson's disease would allow us to test new neuroprotective agents and treatment strategies.