Age-dependent control of dorsal root ganglion neuron survival by macromolecular and low-molecular-weight trophic agents and substratum-bound laminins.

Chick embryo dorsal root ganglion (DRG) neurons can be supported in vitro by nerve growth factor (NGF) and ciliary neuronotrophic factor (CNTF). Pyruvate is also required for survival of neurons from embryonic day 8 (E8) chick ciliary ganglia and from several chick and rat embryonic central nervous system sources. Here we have examined the survival requirements of chick DRG neurons between E6.5 and E15. These DRG neurons, initially dependent only on NGF, become dependent also on CNTF and later on increasingly independent from both factors. Pyruvate nearly doubles neuronal survival at all ages under all conditions. The pyruvate concentration permitting this additional survival was reduced two-fold with serine present. In the presence of polyornithine-bound laminins, nearly all seeded neurons were rescued by pyruvate plus NGF (E8 on), or pyruvate plus CNTF (E10 on), or pyruvate without trophic factors (E15). The same maximal survival was achieved without pyruvate by supplying E10 or older neurons with both NGF and CNTF. Unmodified polyornithine substrata yielded about one-half this number of surviving neurons.