Neuronal cytotoxic edema is implicated in neuronal injury and death, yet mitigating brain edema with osmotic and surgical interventions yields poor clinical outcomes. Importantly, neuronal swelling and its downstream consequences during early brain development remain poorly investigated, and new treatment approaches are needed. We explored Ca²⁺-dependent downstream effects after neuronal cytotoxic edema caused by diverse injuries in mice of both sexes using multiphoton Ca²⁺ imaging in vivo [Postnatal Day (P)12–17] and in acute brain slices (P8–12). After different excitotoxic insults, cytosolic GCaMP6s translocated into the nucleus after a few minutes in a subpopulation of neurons, persisting for hours. We used an automated morphology-detection algorithm to detect neuronal soma and quantified the nuclear translocation of GCaMP6s as the nuclear to cytosolic intensity (N/C ratio). Elevated neuronal N/C ratios occurred concurrently with persistent elevation in Ca²⁺ loads and could also occur independently from neuronal swelling. Electron microscopy revealed that the nuclear translocation was associated with the increased nuclear pore size. The nuclear accumulation of GCaMP6s in neurons led to neocortical circuit dysfunction, mitochondrial pathology, and increased cell death. Inhibiting calpains, a family of Ca²⁺-activated proteases, prevented elevated N/C ratios and neuronal swelling. In summary, in the developing brain, we identified a calpain-dependent alteration of nuclear transport in a subpopulation of neurons after disease-relevant insults leading to long-term circuit dysfunction and cell death. The nuclear translocation of GCaMP6 and other cytosolic proteins after acute excitotoxicity can be an early biomarker of brain injury in the developing brain.

神经元细胞毒性水肿与神经元损伤和死亡有关，但通过渗透和手术干预减轻脑水肿的临床结果不佳。重要的是，在早期大脑发育过程中，神经元肿胀及其下游后果仍然研究不足，需要新的治疗方法。我们使用体内多光子 Ca²⁺ 成像 [出生后日 （P）12-17] 和急性脑切片 （P8-12） 探索了两性小鼠不同损伤引起的神经元细胞毒性水肿后 Ca²⁺ 依赖性下游效应。在不同的兴奋性毒性损伤后，胞质 GCaMP6 在神经元亚群中转移几分钟后转移到细胞核中，持续数小时。我们使用自动形态学检测算法来检测神经元胞体，并将 GCaMP6 的核转位量化为核与胞质强度 （N/C 比率）。神经元 N/C 比值升高与 Ca²⁺ 负荷持续升高同时发生，也可能独立于神经元肿胀发生。电子显微镜显示，核易位与核孔径增加有关。GCaMP6 在神经元中的核积累导致新皮层回路功能障碍、线粒体病理和细胞死亡增加。抑制钙蛋白酶是 Ca²⁺ 激活的蛋白酶家族，可防止 N/C 比率升高和神经元肿胀。总之，在发育中的大脑中，我们在疾病相关损伤导致长期回路功能障碍和细胞死亡后，在神经元亚群中发现了钙蛋白酶依赖性核转运的改变。 急性兴奋性毒性后 GCaMP6 和其他胞质蛋白的核易位可能是发育中大脑损伤的早期生物标志物。