NMDA受体介导的Kv4.3钾通道调控在可卡因增加中脑多巴胺神经元兴奋性及成瘾行为中的作用

Hyperexcitability of VTA DA neurons is one of the important biological characteristics of cocaine addiction. Cocaine induces the remodeling of NMDA receptors, which results in the sustained hyperexcitability of VTA DA neurons, due to functional changes in K+ channels. A type potassium channel Kv4.3 subtype is selectively highly expressed in VTA DA neurons, and regulates neuron excitability in negative feedback mode. Our previous studies have found that activation NMDA receptor of VTA DA neuron could increase IA current, which is a homeostasis adaptive response under physiological state. However, IA current significantly decreased under the cocaine exposure. So how does the effect mentioned above affect cocaine induced hyperexcitability of VTA DA neurons and addictive behavior? We predict that cocaine changes the role of NMDA receptors in regulating Kv4.3 function, thereby increasing the excitability of VTA DA neurons and inducing addictive behaviors. For validating the hypothesis, we will perform electrophysiological recordings combined with calcium imaging, conditional knockout and over expression Kv4.3 gene, tracer of neural projection and single-cell molecular biology methods. The regulation of Kv4.3 mediated by NMDA receptor in the VTA-NAc projection, and the effect of which contributs to cocaine induced hyperexcitability of VTA DA neurons and addictive behavior will be observed, which provides new ideas for cocaine addiction and relapsing mechanism.

VTA DA神经元兴奋性增加是可卡因成瘾的重要生物学特征之一。可卡因导致NMDA受体重构，引起VTA DA神经元兴奋性持续增加，其中钾通道功能的改变扮演了重要角色。A型钾通道Kv4.3亚型选择性高表达于VTA DA神经元，负反馈调节神经元兴奋性。前期研究发现，激活VTA DA神经元NMDA受体可以增大IA电流，此为生理状态下的稳态适应性反应；但在可卡因作用下IA电流显著降低。那么上述作用对可卡因增加VTA DA神经元兴奋性及其成瘾行为有何影响？我们推测，可卡因改变NMDA受体调控Kv4.3功能的作用，从而增加VTA DA神经元兴奋性并诱发成瘾行为。本项目拟应用脑片膜片钳联合钙成像、条件性基因敲除和过表达、神经示踪及单细胞分生等技术，研究VTA-NAc环路中NMDA受体介导的Kv4.3调控，以及这一调控对可卡因增加VTA DA神经元兴奋性及成瘾行为的贡献，为可卡因成瘾及复吸的机制提供新思路。

中脑腹侧背盖区（ventral tegmental area, VTA）多巴胺能（DA）神经元在编码奖赏行为和药物成瘾行为中发挥重要作用，其兴奋性异常与可卡因成瘾及复吸行为密切相连。本项目聚焦Kv4钾通道在VTA DA神经元兴奋性调控中的作用，具体研究Kv4钾通道对可卡因增加VTA DA神经元兴奋性的贡献和机制，以及对可卡因成瘾行为的影响。项目利用了脑片膜片钳电生理技术、单细胞PCR、免疫荧光、动物行为观察等方法开展研究。结果表明，Kv4通道参与了可卡因增加VTA DA神经元兴奋性的过程。一方面，可卡因导致Kv4通道调节VTA DA神经元兴奋性的作用减弱，另一方面，可卡因作用下Kv4通道对NMDA受体增加VTA DA神经元兴奋性的作用降低，其机制与Kv4钾通道功能下降，以及Kv4通道调节NMDA电流的作用减弱有关。上述现象可能与NMDA受体NR2B亚单位有密切关系。此外，调控Kv4通道Kv4.3亚型的功能可影响可卡因诱发的动物成瘾后复吸行为。本项目研究结果提供了可卡因增加VTA DA神经元兴奋性的新机制，为了解与VTA DA神经元兴奋性相关的药物成瘾后复吸机制提供新的实验证据，为可卡因成瘾的相关治疗提供新的靶点。

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