Glial control of neuronal excitability in mammals : I. Electrophysiological and isotopic evidence in culture.
Most of the cells in month-old dissociated cultures of newborn rat cerebral cortex have the morphological (including ultrastructural) features of differentiated astrocytes. They contain significant amounts of the glial fibrillary acidic protein. Their electrophysiological properties are the same as those described for astrocytes in vivo. A multidisciplinary approach was used to study potassium transport in these cultures. (Na(+), K(+))-ATPase activity (?MPi.mg Prot(?1).60 min(?1)) is 1.76+/-0.31 at 3 mMK(+), 2.50+/-0.31 at 10 mMK(+) and 2.70+/-0.26 at 20 mMK(+). The electrogenic component of the membrane potential is 1.77 mV at 3 mMK(+), 3.58 mV at 10 mMK(+) and 4.79 mV at 20 mMK(+) (measurements obtained by intracellular recordings during microperfusion of single cells. Membrane resistance was checked by intracellular pulses applied through a bridge balance). (43)K(+) uptake is ouabain sensitive and increases from 26.39+/-2.43 nMK(+).mg Prot(?1).min(?1) at 3 mMK(+) to 61.96+/-6.50 at 10 mMK(+) and 73.36+/-1.45 at 20 mMK(+). It is concluded from these data that astrocytes have membrane properties consistent with a possible role in controlling extracellular potassium concentration in brain through a Na(+)?K(+) linked active transmembraneous transport.
Moonen
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G
Institut de Médecine - Secteur de Neurologie Hôpital de Bavière - B-4020 Liège - Belgium.
Franck
G
G
Schoffeniels
E
E