Journal of Neuroscience, Vol 4, 1527-1534, Copyright © 1984 by Society for Neuroscience
Astrocytes in primary culture have chemically activated sodium channels
CL Bowman, HK Kimelberg, MV Frangakis, Y Berwald-Netter and C Edwards
The effects of two neurotoxins, veratridine and alpha-scorpion toxin II, on
the resting potential (RMP) of identified astrocytes in primary cell
culture were studied using standard electophysiological techniques.
Veratridine caused either a series of transient depolarizations or a single
sustained depolarization. alpha-Scorpion toxin (II), which alone had no
effect on the RMP, increased the duration of the veratridine-induced
transient depolarizations. The depolarization caused by veratridine, or
veratridine plus alpha- scorpion toxin II, was reversibly inhibited by
tetrodotoxin and was reversibly reduced in magnitude by reductions of the
external sodium concentration. Cells that were depolarized by veratridine
were shown to contain glial fibrillary acidic protein, a marker considered
specific for astrocytes. The effect of long-term (10 sec) hyperpolarizing
and depolarizing current pulses on the RMP were also studied using two
microelectrodes, i.e., dual impalement. In the absence of veratridine, the
RMP returned to its original value after termination of the hyperpolarizing
current, and the current-voltage relationship was found to be linear over a
wide range of membrane potentials. In the presence of veratridine,
termination of the hyperpolarizing current produced a transient
depolarization that was sensitive to tetrodotoxin. Depolarizing current
pulses were without effect. These results show that astrocytes in primary
culture have a chemically inducible Na+ channel that appears to be
voltage-dependent.