Huntington's disease (HD) is a fatal, hereditary neurodegenerative disorder that predominantly affects striatal medium-sized spiny neurons and cortical pyramidal neurons (CPNs). It has been proposed that perturbations in Ca²⁺ homeostasis could play a role in CPN alterations. To test this hypothesis, we used the R6/2 mouse model of juvenile HD at different stages of disease progression; presymptomatic, early symptomatic, and late symptomatic. We combined whole-cell patch clamp recordings of layer 2/3 CPNs with two-photon laser scanning microscopy to image somatic and dendritic Ca²⁺ transients associated with evoked action potentials (APs). We found that the amplitude of AP-induced Ca²⁺ transients recorded at the somata of CPNs was significantly reduced in presymptomatic and late symptomatic R6/2 mice compared to wildtype (WT) littermates. However, reduced amplitudes were compensated by increases in decay times, so that Ca²⁺ transient areas were similar between genotypes. AP-induced Ca²⁺ transients in CPN proximal dendrites were variable and differences did not reach statistical significance, except for reduced areas in the late symptomatic group. In late symptomatic mice, a specific store-operated Ca²⁺ channel antagonist, EVP4593, reduced somatic Ca²⁺ transient amplitude similarly in WT and R6/2 CPNs. In contrast, dantrolene, a ryanodine receptor (RyR) antagonist, and nifedipine, an L-type Ca²⁺ channel blocker, significantly reduced both somatic Ca²⁺ transient amplitude and area in R6/2 but not WT CPNs. These findings demonstrate that perturbations of Ca²⁺ homeostasis and compensation occur in CPNs before and after the onset of overt symptoms, and suggest RyRs and L-type Ca²⁺ channels as potential targets for therapeutic intervention.

中文翻译：

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亨廷顿病 R6/2 小鼠模型皮质锥体神经元的钙失调和补偿

亨廷顿病 (HD) 是一种致命的遗传性神经退行性疾病，主要影响纹状体中等大小的棘神经元和皮质锥体神经元 (CPN)。有人提出，Ca ²⁺体内平衡的扰动可能在 CPN 改变中起作用。为了验证这一假设，我们在疾病进展的不同阶段使用了 R6/2 幼年 HD 小鼠模型。症状前、早期症状和晚期症状。我们将第 2/3 层 CPN 的全细胞膜片钳记录与双光子激光扫描显微镜相结合，对与诱发动作电位 (AP) 相关的体细胞和树突 Ca ^{2+瞬态进行成像。}我们发现 AP 诱导的 Ca ^2+的幅度与野生型 (WT) 同窝小鼠相比，在症状前和症状晚期的 R6/2 小鼠中，CPN 胞体记录的瞬变显着减少。然而，衰减时间的增加补偿了振幅的降低，因此基因型之间的 Ca ²⁺瞬态区域相似。AP 诱导的 CPN 近端树突 Ca ²⁺瞬变是可变的，差异没有达到统计学意义，除了晚期症状组的面积减少。在晚期症状小鼠中，特定的储存操作的 Ca ²⁺通道拮抗剂 EVP4593在 WT 和 R6/2 CPNs 中类似地降低了体细胞 Ca ^{2+瞬态幅度。}相比之下，丹曲林，一种兰尼碱受体 (RyR) 拮抗剂，和硝苯地平，一种 L 型 Ca ²⁺通道阻滞剂，显着降低 R6/2 中的体细胞 Ca ²⁺瞬时幅度和面积，但不降低 WT CPN。这些发现表明，Ca ²⁺稳态和补偿的扰动发生在明显症状发作前后的 CPN 中，并表明 RyRs 和 L 型 Ca ²⁺通道是治疗干预的潜在目标。