RT Journal Article
SR Electronic
T1 Preemptive Regulation of Intracellular pH in Hippocampal Neurons by a Dual Mechanism of Depolarization-Induced Alkalinization
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 6997
OP 7004
DO 10.1523/JNEUROSCI.6088-10.2011
VO 31
IS 19
A1 Nataliya Svichar
A1 Susana Esquenazi
A1 Huei-Ying Chen
A1 Mitchell Chesler
YR 2011
UL http://www.jneurosci.org/content/31/19/6997.abstract
AB Numerous studies have documented the mechanisms that regulate intracellular pH (pHi) in hippocampal neurons in response to an acid load. Here, we studied the response of pHi to depolarization in cultured hippocampal neurons. Elevation of external K+ (6–30 mm) elicited an acid transient followed by a large net alkaline shift. Similar responses were observed in acutely dissociated hippocampal neurons. In Ca2+-free media, the acid response was curtailed and the alkaline shift enhanced. DIDS blocked the alkaline response and revealed a prolonged underlying acidification that was highly dependent on Ca2+ entry. Similar alkaline responses could be elicited by AMPA, indicating that this rise in pHi was a depolarization-induced alkalinization (DIA). The DIA was found to consist of Cl−-dependent and Cl−-independent components, each accounting for approximately one-half of the peak amplitude. The Cl−-independent component was postulated to arise from operation of the electrogenic Na+–HCO3− cotransporter NBCe1. Quantitative PCR and single-cell multiplex reverse transcription-PCR demonstrated message for NBCe1 in our hippocampal neurons. In neurons cultured from Slc4a4 knock-out (KO) mice, the DIA was reduced by approximately one-half compared with wild type, suggesting that NBCe1 was responsible for the Cl−-independent DIA. In Slc4a4 KO neurons, the remaining DIA was virtually abolished in Cl−-free media. These data demonstrate that DIA of hippocampal neurons occurs via NBCe1, and a parallel DIDS-sensitive, Cl−-dependent mechanism. Our results indicate that, by activating net acid extrusion in response to depolarization, hippocampal neurons can preempt a large, prolonged, Ca2+-dependent acidosis.