Journal of Neuroscience, Vol 7, 101-109, Copyright © 1987 by Society for Neuroscience
Ionic channels in mouse astrocytes in culture
L Nowak, P Ascher and Y Berwald-Netter
We observed Na, K, and Cl voltage-dependent currents in a patch-clamp study
of mouse brain astrocytes. In whole-cell recordings, depolarizations
activated inward currents that were identified as Na currents since they
were blocked by TTX, although complete block required high concentrations
(greater than 1 microM). The corresponding single-channel Na currents were
observed in outside-out patches. The channels were opened by a depolarizing
pulse applied from a holding potential identical to the resting potential
(-70 to -80 mV). Therefore, they may be considered functional Na channels.
After addition of veratridine and an alpha-scorpion toxin, the decay of Na
currents in whole-cell recordings was slower than observed under control
conditions. At the single-channel level, the channels appeared to open in
bursts. Depolarization did not increase the duration of the bursts, but
inside each burst, increased the time spent in the open state. The K
currents observed in the whole-cell recording mode were separated into
inactivating and noninactivating currents. The inactivating current
resembled the A current in its kinetics, its insensitivity to
tetraethylammonium, and its sensitivity to 4- aminopyridine. At the
single-channel level, at least 3 classes of K channels were observed at
steady depolarized potentials. They resembled the K channels found in
chromaffin cells by Marty and Neher (1985). Large conductance channels (385
pS) activated around 0 mV were identified as Cl channels.