A furosemide-sensitive K+-Cl- cotransporter counteracts intracellular Cl- accumulation and depletion in cultured rat midbrain neurons.
Efficacy of postsynaptic inhibition through GABAA receptors in the mammalian brain depends on the maintenance of a Cl- gradient for hyperpolarizing Cl- currents. We have taken advantage of the reduced complexity under which Cl- regulation can be investigated in cultured neurons as opposed to neurons in other in vitro preparations of the mammalian brain. Tightseal whole-cell recording of spontaneous GABAA receptor-mediated postsynaptic currents suggested that an outward Cl- transport reduced dendritic [Cl-]i if the somata of cells were loaded with Cl- via the patch pipette. We determined dendritic and somatic reversal potentials of Cl- currents induced by focally applied GABA to calculate [Cl-]i during variation of [K+]o and [Cl-] in the patch pipette. [Cl-]i and [K+]o were tightly coupled by a furosemide-sensitive K+-Cl- cotransport. Thermodynamic considerations excluded the significant contribution of a Na+-K+-Cl- cotransporter to the net Cl- transport. We conclude that under conditions of normal [K+]o the K+-Cl- cotransporter helps to maintain [Cl-]i at low levels, whereas under pathological conditions, under which [K+]o remains elevated because of neuronal hyperactivity, the cotransporter accumulates Cl- in neurons, thereby further enhancing neuronal excitability.
Jarolimek
W
W
I. Physiologisches Institut der Universität Heidelberg, D-69120 Heidelberg, Germany.
Lewen
A
A
Misgeld
U
U
D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003712:Dendrites / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D004232:Diuretics / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005665:Furosemide / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008636:Mesencephalon / Q000166:cytology; D009474:Neurons / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D027981:Symporters; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology; D000096922:K Cl- Cotransporters
D002352:Carrier Proteins; D002712:Chlorides; D004232:Diuretics; D005665:Furosemide; D011188:Potassium; D027981:Symporters; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D000096922:K Cl- Cotransporters