Lu Han, Garg Shreyash, Lenz Maximilian, Vlachos Andreas
Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
BrainLinks-BrainTools Center, University of Freiburg, 79104 Freiburg, Germany.
bioRxiv. 2025 Feb 25:2025.02.23.639712. doi: 10.1101/2025.02.23.639712.
Repetitive transcranial magnetic stimulation (rTMS) is well known for its ability to induce synaptic plasticity, yet its impact on structural and functional remodeling within stimulated networks remains unclear. This study investigates the cellular and network-level mechanisms of rTMS-induced plasticity using a clinically approved 600-pulse intermittent theta burst stimulation (iTBS600) protocol applied to organotypic brain tissue cultures.
We applied iTBS600 to entorhino-hippocampal organotypic tissue cultures and conducted a 24-hour analysis using c-Fos immunostaining, whole-cell patch-clamp recordings, time-lapse imaging of dendritic spines, and calcium imaging.
We observed long-term potentiation (LTP) of excitatory synapses in dentate granule cells, characterized by increased mEPSC frequencies and spine remodeling over time. c-Fos expression in the dentate gyrus was transient and exhibited a clear sensitivity to the orientation of the induced electric field, suggesting a direction-dependent induction of plasticity. Structural remodeling of dendritic spines was temporally linked to enhanced synaptic strength, while spontaneous firing rates remained stable during the early phase in the dentate gyrus, indicating the engagement of homeostatic mechanisms. Despite the widespread electric field generated by rTMS, its effects were spatially and temporally precise, driving Hebbian plasticity and region-specific spine dynamics.
These findings provide mechanistic insights into how rTMS-induced LTP promotes targeted plasticity while preserving network stability. Understanding these interactions may help refine stimulation protocols to optimize therapeutic outcomes.
重复经颅磁刺激（rTMS）以其诱导突触可塑性的能力而闻名，但其对受刺激网络内结构和功能重塑的影响仍不清楚。本研究使用临床批准的600脉冲间歇性theta爆发刺激（iTBS600）方案，应用于脑片组织培养，研究rTMS诱导可塑性的细胞和网络水平机制。
我们将iTBS600应用于内嗅-海马脑片组织培养，并使用c-Fos免疫染色、全细胞膜片钳记录、树突棘的延时成像和钙成像进行了24小时分析。
我们观察到齿状颗粒细胞中兴奋性突触的长期增强（LTP），其特征是随着时间的推移微小兴奋性突触后电流（mEPSC）频率增加和脊柱重塑。齿状回中的c-Fos表达是短暂的，并且对诱导电场的方向表现出明显的敏感性，表明可塑性的方向依赖性诱导。树突棘的结构重塑在时间上与增强的突触强度相关，而在齿状回的早期阶段自发放电率保持稳定，表明稳态机制的参与。尽管rTMS产生了广泛的电场，但其影响在空间和时间上是精确的，驱动了赫布可塑性和区域特异性脊柱动力学。
这些发现为rTMS诱导的LTP如何促进靶向可塑性同时保持网络稳定性提供了机制性见解。理解这些相互作用可能有助于优化刺激方案以提高治疗效果。
