Cl- uptake promoting depolarizing GABA actions in immature rat neocortical neurones is mediated by NKCC1

J Physiol. 2004 Jun 15;557(Pt 3):829-41. doi: 10.1113/jphysiol.2004.062471. Epub 2004 Apr 16.


GABA is the principal inhibitory neurotransmitter in the mature brain, but during early postnatal development the elevated [Cl(-)](i) in immature neocortical neurones causes GABA(A) receptor activation to be depolarizing. The molecular mechanisms underlying this intracellular Cl(-) accumulation remain controversial. Therefore, the GABA reversal potential (E(GABA)) or [Cl(-)](i) in early postnatal rat neocortical neurones was measured by the gramicidin-perforated patch-clamp method, and the relative expression levels of the cation-Cl(-) cotransporter mRNAs (in the same cells) were examined by semiquantitative single-cell multiplex RT-PCR to look for statistical correlations with [Cl(-)](i). The mRNA expression levels were positively (the Cl(-) accumulating Na(+),K(+)-2Cl(-) cotransporter NKCC1) or negatively (the Cl(-) extruding K(+)-Cl(-) cotransporter KCC2) correlated with [Cl(-)](i). NKCC1 mRNA expression was high in early postnatal days, but decreased during postnatal development, whereas KCC2 mRNA expression displayed the opposite pattern. [Cl(-)](i) and NKCC1 mRNA expression were each higher in cortical plate (CP) neurones than in the presumably older layer V/VI pyramidal neurones in a given slice. The pharmacological effects of bumetanide on E(GABA) were consistent with the different expression levels of NKCC1 mRNA. These data suggest that NKCC1 may play a pivotal role in the generation of GABA-mediated depolarization in immature CP cells, while KCC2 promotes the later maturation of GABAergic inhibition in the rat neocortex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Chlorides / metabolism*
  • Fluorescent Dyes
  • Fura-2
  • Gramicidin / pharmacology
  • Homeostasis / physiology
  • In Vitro Techniques
  • Neocortex / drug effects
  • Neocortex / metabolism*
  • Neurons / drug effects
  • Neurons / metabolism*
  • Patch-Clamp Techniques
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Rats
  • Receptors, GABA-A / drug effects
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sodium-Potassium-Chloride Symporters / biosynthesis
  • Sodium-Potassium-Chloride Symporters / genetics
  • Sodium-Potassium-Chloride Symporters / physiology*
  • Solute Carrier Family 12, Member 1
  • Solute Carrier Family 12, Member 2
  • gamma-Aminobutyric Acid / pharmacology*


  • Chlorides
  • Fluorescent Dyes
  • RNA, Messenger
  • Receptors, GABA-A
  • Slc12a1 protein, rat
  • Slc12a2 protein, rat
  • Sodium-Potassium-Chloride Symporters
  • Solute Carrier Family 12, Member 1
  • Solute Carrier Family 12, Member 2
  • Gramicidin
  • gamma-Aminobutyric Acid
  • Fura-2