Transmitter-operated channels in rabbit retinal astrocytes studied in situ by whole-cell patch clamping.
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.
Clark
B
B
Department of Physiology, University College and Middlesex School of Medicine, London, United Kingdom.
Mobbs
P
P
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001640:Bicuculline / Q000494:pharmacology; D018118:Chloride Channels; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007608:Kainic Acid / Q000494:pharmacology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000187:drug effects / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology; D011817:Rabbits; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D012160:Retina / Q000502:physiology*; D013997:Time Factors; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018118:Chloride Channels; D005971:Glutamates; D007473:Ion Channels; D008565:Membrane Proteins; D011963:Receptors, GABA-A; D007051:Ibotenic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D016318:Quisqualic Acid; D007608:Kainic Acid; D001640:Bicuculline