Pathological striatopallidal neuronalensembles in learned motor impairment in PD

摘要 在帕金森病(PD)中，多巴胺(DA)能神经元的变性导致严重的运动障碍。 虽然运动症状最初可以用多巴胺前体左旋多巴(L-多巴)治疗，但患者会经历困难。 导致运动波动，包括L-多巴的作用时间缩短，仅部分治疗 药理手段和脑深部刺激。防止L-多巴的有效性下降将大大 提高患者生活质量，降低社会成本。与失能电机波动的出现有关 随着L-多巴的抗帕金森反应的一个成分的下降，被称为长持续时间反应 (Ldr)。低密度脂蛋白是一种持久的运动改善，在L-多巴血浆水平恢复后持续很长时间 转向基线，在L-多巴停药后数小时至数天内逐渐衰退。马达 LDR下降过快可能会引起波动，阻止LDR衰减的治疗可能会防止更多的波动。 托尔波动。然而，LDR背后的机制目前尚不清楚。使用两种不同的运动任务， 我们最近发现，LDR的诱导和衰退都是任务特有的，需要任务暴露的配对 使用L-多巴(用于LDR诱导)或L-DOPA停药(用于LDR衰减)。这些结果指向Associa- 学习和神经可塑性是其潜在的机制。此外，间接途径培养基刺状 神经元(IMSN)被LDR衰变激活，而D2受体(D2R)基因敲除大大减缓了LDR衰变。 根据上述结果和以前的发现，i)IMSN激活抑制运动，也可能- 主要作用是抑制竞争反应；ii)当iMSN经历异常的长时程增强(LTP)时 DA耗尽，我们将检验LDR衰变过程中逐渐的运动障碍是由异常引起的假设 在正常运动过程中通常被D2R刺激抑制的特定iMSN集合中的LTP- 但在任务暴露期间，如果DA耗尽，就会变得病理性活跃。用Drd2-EGFP小鼠标记 IMSNS，我们将首先考察L-DOPA救治的运动成绩与LDR衰退是否激活不同 同一鼠标中的IMSN集成：我们将在第一个时间点使用 Fos启动子驱动，多西环素门控荧光团，然后TAG任务激活的IMSN集成在第二次 使用内源性Fos标记的点，并比较它们的共定位。然后我们将研究这一点 在LDR衰变过程中被激活的“不正确的”IMSN集合(由Fos驱动的荧光团可视化)具有突触 与LTP的发生一致的输入更改。最后，我们将使用Fos驱动的OPSIN来对 定向地调节这个“不正确的”IMSN集合，以显示其因果和病理作用：它的激活 会导致特定于任务的运动损伤，其抑制会导致特定于任务的运动损伤。由示威者- 在帕金森病患者的任务特异性运动障碍中，病理性IMSN集合的存在和作用， 通过识别导致他们在运动中招募的异常神经可塑性的形式，这些 实验将成为未来研究的基础，以开发新的治疗方法来阻止或逆转LDR衰退和 马达波动。

ABSTRACT In Parkinson's disease (PD), degeneration of dopaminergic (DA) neurons leads to profound motor impairment. Although motor symptom is initially treatable by the DA precursor levodopa (L-DOPA), patients experience dis- abling motor fluctuations, including a shortened duration of action for L-DOPA, only partially treated with pharmacological means and deep brain stimulation. Preventing L-DOPA's declining effectiveness will greatly improve patients' quality of life and reduce social cost. Emergence of disabling motor fluctuation is associated with the decline of a component of L-DOPA's antiparkinsonian response, known as the long duration response (LDR). The LDR is a long-lasting motor improvement that persists long after L-DOPA plasma level has re- turned to baseline, gradually decaying over many hours to days after discontinuation of L-DOPA. Motor fluctuation may be caused by LDR declining too rapidly, and treatments that halt LDR decay may prevent mo- tor fluctuations. However, the mechanism underlying LDR is currently unknown. Using two distinct motor tasks, we recently found that both induction and decay of LDR is task-specific, requiring the pairing of task exposure with L-DOPA (for LDR induction) or with L-DOPA withdrawal (for LDR decay). These results point to associa- tive learning and neuroplasticity as the underlying mechanism. Furthermore, indirect pathway medium spiny neurons (iMSNs) are activated by LDR decay, and D2 receptor (D2R) knockout greatly slowed LDR decay. Based on the above results and previous findings that i) iMSN activation suppresses movement and may nor- mally function to inhibit competing responses; ii) iMSNs undergo aberrant long-term potentiation (LTP) when DA depleted, we will test the hypothesis that gradual motor impairment during LDR decay results from aberrant LTP in specific ensembles of iMSNs that are normally suppressed during normal movement by D2R stimula- tion, but become pathologically active during task exposure if DA is depleted. Using Drd2-EGFP mice to label iMSNs, we will first examine whether L-DOPA-rescued motor performance vs. LDR decay activate different iMSN ensembles in the same mouse: we will tag task-activated iMSN ensemble at the 1st time point using a Fos-promoter driven, doxycycline-gated fluorophore, then tag task-activated iMSN ensemble at the 2nd time point using endogenous Fos labeling, and compare their co-localization. We will then examine whether this “incorrect” iMSN ensemble activated during LDR decay (visualized by a Fos-driven fluorophore) has synaptic input changes that are consistent with the occurrence of LTP. Finally, we will use Fos-driven opsins to bi- directionally modulate this “incorrect” iMSN ensemble to show its causal, pathological role: that its activation leads to task-specific motor impairment, and its inhibition recues impairment task-specifically. By demonstrat- ing the existence of, and the role of, pathological iMSN ensembles in task-specific motor impairment in PD, and by identifying the form of aberrant neuroplasticity that leads to their recruitment during movement, these experiments will form a basis for future studies to develop novel treatments to halt or reverse LDR decay and motor fluctuation.