The effect of acidosis on adenosine release from cultured rat forebrain neurons

During cerebral ischemia, dysregulated glutamate release activates N-methyl-d-aspartate (NMDA) receptors which promotes excitotoxicity and intracellular acidosis. Ischemia also induces cellular adenosine (ADO) release, which activates ADO receptors and reduces neuronal injury. The aim of this research was to determine if decreasing intracellular pH (pHi) enhances ADO release from neurons. Rat forebrain neurons were incubated with NMDA, acetate, propionate, 5-(N)-ethyl-N-isopropyl amiloride (EIPA) or low pH buffer. pHi was determined with the fluorescent dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM) and cellular release of ADO was assayed. NMDA decreased pHi and increased ADO release from neurons. Acetate and propionate decreased pHi and evoked ADO release from neurons. EIPA, an inhibitor of sodium hydrogen exchanger 1 (NHE1), enhanced the acidosis in neurons but did not enhance ADO release. Decreasing extracellular pH (pHe) to 6.8 or 6.45 significantly decreased pHi in neurons, but was not consistently associated with increased ADO release. The main finding of this study was that acidosis per se did not enhance ADO release from neurons.