Roles of specific glutamate receptor subunits in the cerebellar long-term depression

特定谷氨酸受体亚基在小脑长期抑郁中的作用

• 批准号: 09480240
• 负责人: HIRANO Tomoo
• 金额: $ 8.77万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09480240/
• 关键词: cerebellum; synaptic plasticity; long-term depression; Purkinje cell; glutamate receptor; excitatory postsynaptic current; 興奮性シナプス電流

The cerebellar long-term depression (LTD) has been a candidate mechanism for motor learning. It is the long-lasting reduction of transmission efficacy at the granule neuron-Purkinje neuron (G-P) synapses induced by repeated conjunctive activation of an inferior olivary neuron and granule neurons. We have been analyzing cellular and molecular induction mechanism of the LTD in dissociated cell culture preparation, and have demonstrated the involvement of mGluR1 subtype of metabotropic glutamate receptors, δ2 subunit of ionotropic glutamate receptors and IP3 in the LTD induction have been reported. We examined whether MAP kinase is involved or not, and have found that PD98059, an inhibitor of MAP kinase cascade, inhibits the LTD induction, and that the conditioning stimulation inducing LTD activates MAP kinase. PD98059 suppressed the inward current induced by application of a mGluR1 agonist to a Purkinje cell, which suggests that MAP kinase activity supports the mGluR1 cascade. We also succeeded to monitor synaptic efficacy for a week after the LTD induction by measuring the miniature EPSCs amplitude before and after the LTD induction in the culture. By this method, we demonstrated that the synaptic efficacy recovers in two days after the LTD induction and that the LTD is consist of early and late phases whose induction mechanisms are distinct. The late phase required the prolonged conditioning stimulation for the induction and was dependent on both mRNA and protein syntheses. The study to clarify roles of δ2 subunit in the LTD induction is on going, using cultured Purkinje neurons prepared form δ2 knockout mice and the adeno-virus vector to express mutant δ2 proteins.

小脑长期抑制（LTD）已成为运动学习的候选机制。它是由下橄榄神经元和颗粒神经元的反复联合激活诱导的颗粒神经元-浦肯野神经元（G-P）突触处的传递效力的长期持续降低。我们在分离的细胞培养物中分析了LTD的细胞和分子诱导机制，并证实了代谢型谷氨酸受体的mGluR 1亚型、离子型谷氨酸受体的δ2亚基和IP 3参与LTD的诱导。我们研究了MAP激酶是否参与其中，发现MAP激酶级联抑制剂PD 98059抑制LTD的诱导，而诱导LTD的条件刺激激活MAP激酶。PD 98059抑制由应用mGluR 1激动剂至浦肯野细胞诱导的内向电流，这表明MAP激酶活性支持mGluR 1级联。我们还成功地监测突触效能一周后，LTD诱导通过测量微型EPSC振幅之前和之后的LTD诱导的文化。通过这种方法，我们证明了突触效能在LTD诱导后两天内恢复，并且LTD由早期和晚期相组成，其诱导机制不同。晚期需要长时间的条件刺激来诱导，并且依赖于mRNA和蛋白质的合成。利用δ2基因敲除小鼠培养的浦肯野神经元和腺病毒载体表达突变体δ2蛋白，阐明δ2亚基在LTD诱导中的作用。

项目成果

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