A 30-s 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)-carboxyfluorescein. This intracellular acidification could be blocked by addition of the NMDA antagonist, D-(-)-2-amino-5-phosphonovalerate, 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'-disulfonic acid or 4- acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, 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, did not affect pH recovery. Removal of extracellular Cl- 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.
Recovery from NMDA-induced intracellular acidification is delayed and dependent on extracellular bicarbonate
Sensi S. L.Co-primo
;
1996-01-01
Abstract
A 30-s 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)-carboxyfluorescein. This intracellular acidification could be blocked by addition of the NMDA antagonist, D-(-)-2-amino-5-phosphonovalerate, 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'-disulfonic acid or 4- acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid, 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, did not affect pH recovery. Removal of extracellular Cl- 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
