Astrocytic GABA receptors.
GABA receptors are distributed widely throughout the central nervous system on a variety of cell types. It has become increasingly clear that astrocytes, both in cell culture and tissue slices, express abundant GABAA receptors. In astrocytes, GABA activates Cl(-)-specific channels that are modulated by barbiturates and benzodiazepines; however, the neuronal inverse agonist methyl-4-ethyl-6, 7-dimethoxy-beta-carboline-3-carboxylate enhances the current in a subpopulation of astrocytes. The properties of astrocytic GABAA receptors, therefore, are remarkably similar to their neuronal counterparts, with only a few pharmacological exceptions. In stellate glial cells of the pituitary pars intermedia, GABA released from neuronal terminals activates postsynaptic potentials directly. The physiological significance of astrocytic GABAA-receptor activation remains unknown, but it may be involved in extracellular ion homeostasis and pH regulation. At present, there is considerably less evidence for the presence of GABAB receptors on astrocytes. The data that have emerged, however, indicate a prominent role for second-messenger regulation by this receptor.
Fraser
D D
DD
Neuroscience Research Group, University of Calgary, Alberta, Canada.
Mudrick-Donnon
L A
LA
MacVicar
B A
BA
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001418:Baclofen / Q000494:pharmacology; D001463:Barbiturates / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D002243:Carbolines / Q000494:pharmacology; D002415:Cats; D018118:Chloride Channels / Q000145:classification / Q000187:drug effects / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D009118:Muscimol / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology; D010902:Pituitary Gland / Q000166:cytology; D051381:Rats; D018079:Receptors, GABA / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D015290:Second Messenger Systems; D009435:Synaptic Transmission / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D001463:Barbiturates; D002243:Carbolines; D018118:Chloride Channels; D018756:GABA Antagonists; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D018079:Receptors, GABA; D001569:Benzodiazepines; C034818:methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001418:Baclofen