Journal of Neuroscience, Vol 12, 664-673, Copyright © 1992 by Society for Neuroscience
Transmitter-operated channels in rabbit retinal astrocytes studied in situ by whole-cell patch clamping
B Clark and P Mobbs
Department of Physiology, University College and Middlesex School of Medicine, London, United Kingdom.
Glutamate and GABA open ion channels in the membranes of astrocytes found
on the vitreal surface of the rabbit retinal visual streak. The
glutamate-operated channels are opened by kainate, quisqualate, and AMPA,
but not by NMDA, aspartate, or the metabotropic agonist 1-
aminocyclopentane-1 S,3R-dicarboxylic acid. The effects of glutamate and
its analogs can be blocked by 20 microM 6-cyano-7-nitroquinoxaline-
2,3-dione. The conductance increase evoked by 10 microM glutamate, a
concentration of this transmitter near to that found in the vitreous humor
that bathes these cells, was equivalent to 22% of the cell's resting
conductance. The conductance increase evoked by 1 microM GABA, a
concentration near that found in the vitreous, was equivalent to 131% of
the cell's resting conductance. The effects of GABA can be blocked by
bicuculline. These data show that GABA, and non-NMDA-type glutamate
receptors play an important part in determining the resting potential of
visual streak astrocytes in situ and that these channels may be of general
importance for the functions of astrocytes in vivo.