A new framework for assessment of potassium-buffering mechanisms.

A new concept, that of "buffer capacity," is defined for potassium-buffering mechanisms in neural tissue. Buffer capacities for different mechanisms can be added and compared, thus simplifying quantitative assessment of diffusion, cytoplasmic uptake, and spatial buffering under varied conditions. The characteristic frequency components for potassium disturbances due to neural events are identified. The effect of buffering by a reservoir of fluid at a tissue surface is analyzed, together with its intrinsic limitations. The role of retinal Müller cells in spatial buffering is considered quantitatively: both buffering to the tissue surface and buffering sideways through cell-to-cell connections.