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Keywords:

  • GABAA receptor;
  • Na+–K+–2Cl transporter;
  • neuronal progenitor

Abstract

Neuronal progenitors are continuously generated in the postnatal rodent subventricular zone and migrate along the rostral migratory stream to supply interneurons in the olfactory bulb. Nonsynaptic GABAergic signaling affects the postnatal neurogenesis by depolarizing neuronal progenitors, which depends on an elevated intracellular Cl concentration. However, the molecular mechanism responsible for Cl accumulation in these cells still remains elusive. Using confocal Ca2+ imaging, we found that GABA depolarization-induced Ca2+ increase was either abolished by bumetanide, a specific inhibitor of the Na+–K+–2Cl cotransporter, or reduced by partial replacement of extracellular Na+ with Li+, in the HEPES buffer but not in the CO2/inline image buffer. GABA depolarization-induced Ca2+ increase in CO2/inline image buffer was abolished by a combination of bumetanide with the anion exchanger inhibitor DIDS or with the carbonic anhydrase inhibitor acetozalimide. Using gramicidin-perforated patch-clamp recording, we further confirmed that bumetanide, together with DIDS or acetozalimide, reduced the intracellular chloride concentration in the neuronal progenitors. In addition, with BrdU labeling, we demonstrated that blocking of the Na+–K+–2Cl cotransporter, but not anion exchangers, reduced the proliferation of neuronal progenitors. Our results indicate that both the Na+–K+–2Cl cotransporter and anion exchangers contribute to the elevated intracellular chloride responsible for the depolarizing action of GABA in the postnatal forebrain neuronal progenitors. However, the Na+–K+–2Cl cotransporter displays an additional effect on neuronal progenitor proliferation.