Multidomain Model for Optic Nerve Potassium Clearance: Roles of Glial Cells and Perivascular Spaces

TL;DR

This study develops a multi-domain model of the optic nerve to analyze potassium clearance, highlighting the crucial roles of glial cells and perivascular spaces in buffering potassium and fluid circulation, with implications for neurological conditions.

Contribution

The paper introduces a novel multi-domain model incorporating convection, diffusion, and electrical migration to study potassium clearance in the optic nerve, emphasizing glia and perivascular spaces.

Findings

Potassium clearance is mainly driven by convective flow within glial syncytia.

Perivascular space significantly contributes to potassium buffering and fluid circulation.

The model can be adapted to various neural structures with different channel distributions.

Abstract

The accumulation of potassium in the extracellular space surrounding nerve cells is a fundamental aspect of biophysics that has garnered significant attention in recent research. This phenomenon holds implications for various neurological conditions, including spreading depression, migraine, certain types of epilepsy, and potentially, learning processes. A quantitative analysis is essential for understanding the dynamics of potassium clearance following a series of action potentials. This clearance process involves multiple structures along the nerve, including glia, the extracellular space, axons, and the perivascular space, necessitating a spatially distributed systems approach akin to the cable equations of nerve physiology. In this study, we propose a multi-domain model for the optic nerve to investigate potassium accumulation and clearance dynamics. The model accounts for the convection, diffusion, and electrical migration of fluid and ions, revealing the significant roles of glia and the perivascular space in potassium buffering. Specifically, our findings suggest that potassium clearance primarily occurs through convective flow within the syncytia of glia, driven by osmotic pressure differences. Additionally, the perivascular space serves as a crucial pathway for potassium buffering and fluid circulation, further contributing to the overall clearance process. Importantly, our model's adaptability allows for its application to diverse structures with distinct channel and transporter distributions across the six compartments, extending its utility beyond the optic nerve.