Susceptibility to apoptosis is enhanced in immature cortical neurons.

The susceptibility of cortical neurons to two forms of apoptotic death was compared with susceptibility to excitotoxic death during development in vitro (DIV 4-21). Murine cortical cultures were exposed for 48 h to the phosphatase inhibitor cyclosporine, the protein kinase inhibitor staurosporine or the excitotoxin N-methyl-D-aspartate (NMDA). Susceptibility to apoptosis induced by staurosporine or cyclosporine was maximal between DIV 4-10 and declined from DIV 10 through 18. The opposite pattern was observed with susceptibility to NMDA receptor-mediated excitotoxic necrosis, which was minimal at DIV 6 and progressively increased through DIV 21.