We hypothesized that the P2X7 receptor may be the target of isoflurane, so we investigated the roles of the P2X7 receptor and inositol triphosphate receptor in calcium overload and neuronal apoptosis induced by isoflurane in cultured embryonic rat hippocampal neurons. Results showed that isoflurane induced widespread neuronal apoptosis and significantly increased cytoplasmic Ca 2+ . Blockade of P2X7 receptors or removal of extracellular Ca 2+ combined with blockade of inositol triphosphate receptors completely inhibited apoptosis or increase in cytoplasmic Ca 2+ . Removal of extracellular Ca 2+ or blockade of inositol triphosphate receptor alone could partly inhibit these effects of isoflurane. Isoflurane could directly activate P2X7-gated channels and induce inward currents, but did not affect the expression of P2X7 receptor protein in neurons. These findings indicate that the mechanism by which isoflurane induced neuronal apoptosis in rat developing brain was mediated by intracellular calcium overload, which was caused by P2X7 receptor mediated calcium influx and inositol triphosphate receptor mediated calcium release. We hypothesized that the P2X7 receptor may be the target of isoflurane, so we investigated the roles of the P2X7 receptor and inositol triphosphate receptor in calcium overload and neuronal apoptosis induced by isoflurane in cultured embryonic rat hippocampal neurons. Results showed that isoflurane induced widespread neuronal apoptosis and significantly increased cytoplasmic Ca 2+. Blockade of P2X7 receptors or removal of extracellular Ca 2+ combined with blockade of inositol triphosphate receptors either determined apoptosis or increase in cytoplasmic Ca 2+. Removal of extracellular Ca 2+ or blockade of inositol triphosphate receptor alone Isoflurane could directly activate P2X7-gated channels and induce inward currents, but did not affect the expression of P2X7 receptor protein in neurons. These results indicate that the mechanism by which isoflurane-induced neuronal apoptosis in rat developing brain was mediated by intracellula r calcium overload, which was caused by P2X7 receptor mediated calcium influx and inositol triphosphate receptor mediated calcium release.