What does the potassium that astrocytes buffer have to do with spreading depression? · Grey Matter

Every spike leaves potassium in the narrow space between cells, and astrocytes normally take it up and spread it through their coupled network.

What does the potassium that astrocytes buffer have to do with spreading depression?

Every spike leaves potassium in the narrow space between cells, and astrocytes normally take it up and spread it through their coupled network. If potassium and glutamate accumulate faster than astrocytes and pumps can clear them, the local neurons depolarise, release still more of both, and the tissue can cross into a self-sustaining collapse of the gradients. Spreading depression is that collapse travelling: the potassium and glutamate released at the front depolarise the next patch of cortex, and the wave advances at a few millimetres per minute. How easily a cortex supports such a wave depends in part on how well its astrocytes keep the extracellular space clean.