Ca2+ and acidosis synergistically lead to the dysfunction of cortical GABAergic neurons during ischemia

Abstract

Cell death in cerebral ischemia is presumably initiated by neural excitotoxicity resulted from the dysfunction of inhibitory neurons in early stage. Molecular processes underlying the ischemic injury of inhibitory neurons remain to be elusive, which we investigated by biochemical manipulations with cellular imaging and patch clamp at GFP-labeled GABAergic cells in cortical slices. Ischemia induces Ca(2+) elevation, acidosis and dysfunction in GABAergic cells. An elevation of cytoplasmic Ca(2+) or H(+) impairs the encoding of action potentials in these neurons. The effects of Ca(2+) and H(+) are additive in nature and occlude ischemic outcomes. Ischemia impairs spike production through prolonging spike refractory periods and raising threshold potentials. Therefore, calcium toxicity and acidosis during ischemia synergistically impair the dynamics of sodium channels and function of cortical GABAergic neurons, which lead to neural excitotoxicity. Our results also suggest that the cocktail therapeutics is needed to prevent neuronal death from ischemia.