Properties of the proton-evoked currents and their modulation by Ca 2+ and Zn2+ in the acutely dissociated hippocampus CA1 neurons

Jun Gao, Long Jun Wu, Lin Xu, Tian Le Xu

Research output: Contribution to journalArticle

43 Scopus citations

Abstract

The characterization of acid-sensing ion channel (ASIC)-like currents has been reported in hippocampal neurons in primary culture. However, it is suggested that the profile of expression of ASICs changes in culture. In this study, we investigated the properties of proton-activated current and its modulation by extracellular Ca2+ and Zn2+ in neurons acutely dissociated from the rat hippocampal CA1 using conventional whole-cell patch-clamp recording. A rapidly decaying inward current and membrane depolarization was induced by exogenous application of acidic solution. The current was sensitive to the extracellular proton with a response threshold of pH 7.0-6.8 and the pH50 of 6.1, the reversal potential close to the Na+ equilibrium potential. It had a characteristic of acid-sensing ion channels (ASICs) as demonstrated by its sensitivity to amiloride (IC 50=19.6±2.1 μM). Either low [Ca2+]o or high [Zn2+]o increased the amplitude of the current. All these characteristics are consistent with a current mediated through a mixture of homomeric ASIC1a and heteromeric ASIC1a+2a channels and closely replicate many of the characteristics that have been previously reported for hippocampal neurons cultured for a week or more, indicating that culture artifacts do not necessarily flaw the properties of ASICs. Interestingly, we found that high [Zn2+]o (>10-4 M) slowed the decay time constant of the ASIC-like current significantly in both acutely dissociated and cultured hippocampal neurons. In addition, the facilitating effects of low [Ca2+]o and high [Zn2+] o on the ASIC-like current were not additive. Since tissue acidosis, extracellular Zn2+ elevation and/or Ca2+ reduction occur concurrently under some physiological and/or pathological conditions, the present observations suggest that hippocampal ASICs may offer a novel pharmacological target for therapeutic invention.

Original languageEnglish (US)
Pages (from-to)197-207
Number of pages11
JournalBrain Research
Volume1017
Issue number1-2
DOIs
StatePublished - Aug 13 2004

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Keywords

  • Acid-sensing ion channel
  • Cellular and molecular biology
  • Hippocampal CA1 neuron
  • Membrane composition and cell-surface macromolecules
  • Patch-clamp
  • Proton-induced current

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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