Regulation of intracellular pH in pyramidal neurones from the rat hippocampus by Na(+)-dependent Cl(-)-HCO3- exchange

J Physiol. 1994 Feb 15;475(1):59-67. doi: 10.1113/jphysiol.1994.sp020049.


1. We have measured intracellular pH (pHi) in freshly isolated pyramidal neurones from the CA1 region of the rat hippocampus using the fluorescent indicator 2',7'-bis(carboxy-ethyl)-5-(and-6)-carboxyfluorescein (BCECF). 2. The neurones selected by our isolation procedure, when studied in the nominal absence of CO2-HCO3-, had a mean steady-state pHi of 6.81 +/- 0.02 (n = 163). The recovery of pHi from acid loads was very slow. The rate of recovery from acid loads was reduced by Na+ removal, but only very slightly inhibited by 1 mM amiloride. 3. The addition of 5% CO2-25 mM HCO3- caused steady-state pHi to increase from 6.74 +/- 0.05 to 7.03 +/- 0.03 (n = 28). In the presence of 5% CO2-25 mM HCO3-, the rate of pHi recovery from acid loads was much faster than in its absence. 4. The HCO(3-)-induced alkalinization was reversible, and did not occur in the absence of extracellular Na+ or in the presence of DIDS (4,4'-diisothiocyanatostilbene- 2,2'-disulphonic acid). 5. In the absence of external Cl-, successive exposures to CO2-HCO3- elicited alkalinizations that were progressively reduced in rate and amplitude. This effect, presumably due to gradual depletion of internal Cl-, was rapidly reversed by returning Cl- to the external medium. 6. We conclude that the major acid-extrusion mechanism in pyramidal CA1 neurones is the Na(+)-dependent Cl(-)-HCO3- exchanger. The Na(+)-dependent mechanism that operates in the nominal absence of HCO3- is far less active.

Publication types

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

MeSH terms

  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / pharmacology
  • Amiloride / pharmacology
  • Animals
  • Bicarbonates / metabolism*
  • Carbon Dioxide / pharmacology
  • Chlorides / metabolism*
  • Fluoresceins
  • Fluorescent Dyes
  • Hippocampus / cytology
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Ion Exchange
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Sodium / physiology*
  • Spectrometry, Fluorescence


  • Bicarbonates
  • Chlorides
  • Fluoresceins
  • Fluorescent Dyes
  • Carbon Dioxide
  • Amiloride
  • 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein
  • Sodium
  • 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid