Glial modulation of neural excitability mediated by extracellular pH: a hypothesis revisited

Abstract

This chapter discusses an update on a model interaction between astrocytes and neurons based on activity-induced changes in extracellular ion concentrations, K + and H +, mainly, the nature of the astrocyte-induced extracellular acidification, and the manner in which pH changes can alter neural excitability. The proposed interaction represented an example of volume transmission mediated by ions. It was viewed as a negative feedback loop whereby active neurons would signal to nearby astrocytes the extent of their current activity, in the form of graded changes in extracellular K+ concentration, and astrocytes would respond by producing graded degrees of extracellular acidification. The acidification would, in turn, dampen neuronal excitability. It is argued that this feedback system could function to adjust local brain excitability in relationship to ongoing activity; the more intense the activity, the greater the resulting acidification and reduction in excitability.