A genetically encoded ratiometric indicator for chloride: capturing chloride transients in cultured hippocampal neurons

Neuron. 2000 Sep;27(3):447-59. doi: 10.1016/s0896-6273(00)00056-8.


We constructed a novel optical indicator for chloride ions by fusing the chloride-sensitive yellow fluorescent protein with the chloride-insensitive cyan fluorescent protein. The ratio of FRET-dependent emission of these fluorophores varied in proportion to the concentration of Cl and was used to measure intracellular chloride concentration ([Cl-]i) in cultured hippocampal neurons. [Cl-]i decreased during neuronal development, consistent with the shift from excitation to inhibition during maturation of GABAergic synapses. Focal activation of GABAA receptors caused large changes in [Cl-]i that could underlie use-dependent depression of GABA-dependent synaptic transmission. GABA-induced changes in somatic [Cl-]i spread into dendrites, suggesting that [Cl-]i can signal the location of synaptic activity. This genetically encoded indicator will permit new approaches ranging from high-throughput drug screening to direct recordings of synaptic Cl- signals in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cells, Cultured
  • Chlorides / analysis
  • Chlorides / metabolism*
  • Dendrites / metabolism
  • Energy Transfer
  • Fluorescent Dyes
  • Hippocampus / cytology
  • Hippocampus / metabolism*
  • Hydrogen-Ion Concentration
  • Intracellular Fluid / chemistry
  • Intracellular Fluid / metabolism
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Neurons / cytology
  • Neurons / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism*
  • Signal Transduction / physiology
  • Spectrometry, Fluorescence
  • Synapses / metabolism
  • Synaptic Transmission / physiology
  • Transfection
  • gamma-Aminobutyric Acid / metabolism


  • Bacterial Proteins
  • Chlorides
  • Fluorescent Dyes
  • Luminescent Proteins
  • Receptors, GABA-A
  • Recombinant Fusion Proteins
  • clomeleon
  • yellow fluorescent protein, Bacteria
  • gamma-Aminobutyric Acid