Recovery from nmda-induced intracellular acidification in cortical
neurons is delayed and dependent on extracellular bicarbonate.
Canzoniero, L. M. T., S. L. Sensi, and D. W. Choi.
Center for the Study of Nervous System Injury, and Department of
Neurology, Washington University School of Medicine, St. Louis, MO
63110
APStracts 2:0331C, 1995.
A thirty second exposure to N-methyl-D-aspartate (NMDA) produced a
dose-dependent and long-lasting (10-20 min) reduction in
intracellular pH in cultured cortical neurons, detected by the
fluorescent dye 2,7' bis-carboxyethyl 5,6 carboxy-fluorescein
(BCECF). This intracellular acidification could be blocked by
addition of the NMDA antagonist, D(-)-2-amino-5-phosphonovalerate (D
-APV), or by removal of extracellular Ca2+. Removal of extracellular
HCO3- markedly impaired recovery from NMDA-induced intracellular
acidification. Recovery was also impaired when 4,4'
-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) or 4-acetamido
-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS), inhibitors of
HCO3- transport, were added to the cultures immediately after NMDA
exposure. In contrast, the Na+ - H+ exchange blocker, 5-(N-ethyl-N
-isopropyl)amiloride (EIPA) did not affect pH recovery. Removal of
extracellular Cl- ions partially prevented pH recovery after NMDA
stimulation. In addition, extracellular HCO3- increased intracellular
Na+ after NMDA exposure, consistent with HCO3- activation of a Na+
-dependent exchanger. These results demonstrate that stimulation of
cortical neuronal NMDA receptors is followed by long-lasting
intracellular acidification, and that the presence of extracellular
HCO3- is important in the subsequent recovery of normal intracellular
pH, likely acting at least in part via the Na+ -dependent Cl--HCO3-
exchanger.
Received 10 November 1994; accepted in final form 5 September
1995.
APS Manuscript Number C666-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.