Ion activities and potassium uptake mechanisms of glial cells in guinea‐pig olfactory cortex slices.

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Abstract
1. Double-barrelled ion-sensitive micro-electrodes were used to measure changes in the intracellular activities of K+, Na+ and Cl- .**GRAPHIC**. in glial cells of slices from guinea-pig olfactory cortex during repetitive stimulation of the lateral olfactory tract. 2. Base-line levels of .**GRAPHIC**. .**GRAPHIC**. and .**GRAPHIC**. were about 66, 25 and 6 mM, respectively, for cells with resting potentials higher than -80 mV. During stimulation, intraglial .**GRAPHIC**. and .**GRAPHIC**. increased, whereas .**GRAPHIC**. decreased. Within about 2 min after stimulation the ion activities returned to their base-line levels. 3. The Cl- equilibrium potential was found to be close to the membrane potential (Em). There was also a strong correlation between changes of Em and .**GRAPHIC**. These observations indicate a high Cl- conductance of the glial cell membrane. 4. In the presence of Ba2+, the usual depolarizing response of the glial cells to a rise of the extracellular K+ activity .**GRAPHIC**. reversed into a membrane hyperpolarization. Furthermore, Ba2+ strongly reduced the stimulus-related rise of intraglial .**GRAPHIC**. An additional application of ouabain blocked both the membrane hyperpolarization as well as the remaining rise of .**GRAPHIC**. 5. In conclusion, our data show that glial cells in guinea-pig olfactory cortex slices possess at least two mechanisms of K+ accumulation. One mechanism is sensitive to the K+ channel blocker Ba2+ and might be a passive KCl influx. The other appears to be the electrogenic Na+/K+ pump, which can be activated by excess extracellular K+.