Nanoscale and functional heterogeneity of the hippocampal extracellular space

The extracellular space (ECS) and its constituents play a crucial role in brain development, plasticity, circa-dian rhythm, and behavior, as well as brain diseases. Yet, since this compartment has an intricate geometry and nanoscale dimensions, its detailed exploration in live tissue has remained an unmet challenge. Here, we used a combination of single-nanoparticle tracking and super-resolution microscopy approaches to map the nanoscale dimensions of the ECS across the rodent hippocampus. We report that these dimensions are heterogeneous between hippocampal areas. Notably, stratum radiatum CA1 and CA3 ECS differ in several characteristics, a difference that gets abolished after digestion of the extracellular matrix. The dynamics of extracellular immunoglobulins vary within these areas, consistent with their distinct ECS characteristics. Altogether, we demonstrate that ECS nanoscale anatomy and diffusion properties are widely heterogeneous across hippocampal areas, impacting the dynamics and distribution of extracellular molecules.

Automated summary

The extracellular space (ECS) and its constituents have important functions in brain development, plasticity, circadian rhythm, and behavior, as well as brain diseases. However, exploring the nanoscale dimensions of the ECS in live tissue is challenging due to its complex geometry and small size. In this study, using single-nanoparticle tracking and super-resolution microscopy, the nanoscale dimensions of the ECS in the rodent hippocampus were mapped. The results show that these dimensions are heterogeneous between different areas of the hippocampus, and the dynamics and distribution of extracellular molecules are affected by these differences.