Developmental shift in the apostat: comparison of neurones and astrocytes.

The intrinsic pathway of apoptosis was investigated in cell-free extracts of neurones and astrocytes at various stages of maturation. Neuronal extracts were activated 65-fold after 3 days, 9-fold after 7 days, and were not activated after 10 days in culture. In contrast, astrocyte extracts were activated to a similar extent at all stages, up to 60 days in culture. The co-incubation of neuronal and astrocyte extracts followed by addition of cytochrome c/2'-deoxyadenosine 5'-triphosphate led to a 40-fold activation, suggesting that the development-associated neuronal shift does not involve the appearance of a dominant inhibitor, but rather downregulation of some key component(s) involved in caspase activation.