| Co-Investigator(Kenkyū-buntansha) |
NODA Kazuko Kitasato University, School of Allied Health sciences Physiology, Assistant Professor, 医療衛生学部, 講師 (60050704)
AKITA Hisanao Kitasato University, School of Allied Health Sciences Physiology, Associate Professor, 医療衛生学部, 助教授 (70118777)
SUZUKI Nobuyuki Kitasato University, School of Allied Health Sciences Physiology, Associate Professor, 医療衛生学部, 助教授 (10050650)
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| Research Abstract |
Purpose : We hypothesized that a pathogenesis for dyskinesias due to chronic L-DOPA treatment in patients with Parkinson's disease is not dopamine depletion itself but abnormal synaptic plasticity of striatal neurons induced by denervation of dopaminergic fibers. To test this hypothesis, in this study, we armed to produce a novel type of Parkinson's disease model animal that has dopamine depletion without denervation of dopaminergic fibers in the striatum by using antisense-induced nigral knockdown of synaptotagmin I, a regulatory protein of transmitter release machinery.
Research results : 1) We examined by Western blot analysis whether the synaptotagmin I protein level in the hippocampus was down-regulated by antisense ODNs against synaptotagmin I (syt-AS) following the infra-hippocampal I injection of HVJ-liposome vector containing syt-AS. As a result, synaptotagmin level in the hippocampus was down-regulated maximally by 50 % at 4-8 days after the injection. And the down-regulation
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of synaptotagmin protein level by antisense-treatment was sustained for about 10 days. 2) Next, using the HVJ-liposome vector containing this effective antisense ODNs, we produced rats with nigral knockdown of synaptotagmin I by the infra-nigral injection of HVJ-liposome containing syt-AS. Four days after the infra-nigral injection of syt AS, rats with antisense-induced nigral knockdown of synaptotagmin I displayed slight motor dysfunction, rotation responses, in the amphetamine-Induced hyperlocomotion. 3) One day after the behavioral test for motor dysfunction, the rats with unilateral nigral knockdown of synaptotagmin I received bilaterally the implantation of micro-dialysis probe in the striatum. By measurement of dopamine level through the micro-dialysis probes, marked decrease (20-70%) of the amphetamine-induced release of dopamine was observed in the treated side of the striatum, compared with that in the non-treated side. 4) Unlike the 6-OHDA nigral lesion, the antisense-induced nigral knockdown did not cause apomorphine-induecd high expression of c-fos gene, an prominent indicator of abnormal synaptic plasticity, in the dopamine-depleted striatal neurons.
Conclusion : As expected, antisense-induced nigral knockdown of synaptotagmin I produced marked reduction of dopamine release in the striatum. This reduction of dopamine release in the striatum was related to slight motor dysfunction, but the relationship between the dopamine depletion and the motor dysfunction was not linear. From these results, we conclude that rat with synaptotagmin nigral knockdown may be a model animal for early Parkinson's disease. Less
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