Coupling of metabolism and electrical activity in cortical astrocytes

Cortical mouse astrocytes in culture were impaled with two-channel microelectrodes. These mouse astrocytes have the same responses to different K+ concentrations, ouabain, and glutamate as cultured rat astrocytes, with the exception that a large barium-sensitive K+ conductance clamps the membrane potential at the K+ equilibrium potential. Glycolytic and mitochondrial inhibitors have little effect on the mouse astrocytes. Total blockade of energy metabolism leads to an irreversible, calcium-dependent depolarization, but only if applied for longer than 45 min. Increasing the extracellular K+ concentration to 60 mM increases the intracellular K+ concentration by 43 mM and the bicarbonate concentration by 22 mM and leads to a concomitant fast swelling. Together with the 20 mM increase in Cl- concentration reported in the literature this is a good indication for a Boyle- and Conway-mediated K(+)-anion influx with water. This influx is accomplished by the depolarization-induced opening of Cl- channels as reported in the literature. In conclusion, ischemia-like conditions have little direct, immediate impact on astrocytes. In contrast, ischemia-induced release of substances from neurones, such as K+, produces an immediate and fast response.