gamma-Aminobutyric acid-induced ion movements in the guinea pig hippocampal slice.
gamma-Aminobutyric acid (GABA)-induced regional changes of extracellular Cl, K and Na concentration ([Cl]o, [K]o, [Na]o), as well as of the extracellular space were measured with ion-sensitive microelectrodes in guinea pig hippocampal slices. Microdrop application of GABA to the pyramidal cell layer of CA3 or CA1 induced a decrease of [Cl]o, while application to the dendritic layer of CA3 or CA1 induced an increase of [Cl]o in addition. All changes of [Cl]o persisted in the presence of TTX and were blocked by bath-applied bicuculline. The GABA-induced decrease of [Cl]o was reduced by bicuculline application to the pyramidal cell layer. The increase of [Cl]o was blocked by bicuculline application to the dendritic layer. Additionally, GABA induced an increase of [K]o and decreases/increases of [Na]o. Changes of [Cl]o, [K]o and [Na]o together were approximately electroneutral. [Cl]o increases were exaggerated and [Cl]o decreases partly masked by shrinkage of the extracellular space after GABA application. Changing [K] in the superfusate transiently changed GABA-induced [Cl]o movements in a way predicted from a change in driving force due to the effect of [K] on membrane potential. Then a partial recovery followed towards the original [Cl]o change. We conclude that inward and outward Cl transports maintain [Cl]i below equilibrium in CA3 and CA1 pyramidal somata and above equilibrium in CA3 and CA1 dendrites. The significance of this Cl-distribution for hippocampal inhibition is discussed.
Müller
W
W
Department of Neurophysiology, Max-Planck-Institut für Psychiatrie, Planegg-Martinsried, F.R.G.
Misgeld
U
U
Lux
H D
HD
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002712:Chlorides / Q000502:physiology*; D004558:Electric Stimulation; D006168:Guinea Pigs; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D001640:Bicuculline; D002712:Chlorides; D007473:Ion Channels; D010852:Picrotoxin; D011188:Potassium; D012964:Sodium; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid