The signaling mechanisms that control the survival of CNS neurons are poorly understood. Here we show that, in contrast to PNS neurons, the survival of purified postnatal rat retinal ganglion cells (RGCs) in vitro is not promoted by peptide trophic factors unless their intracellular cAMP is increased pharmacologically or they are depolarized by K÷ or glutamate agonists. Long-term survival of most RGCs in culture can be promoted by a combination of trophic factors normally produced along the visual pathway, including BDNF, CNTF, IGF1, an oligodendrocyte-derived protein, and forskolin. These results suggest that neurotransmitter stimulation and electrical activity enhance the survival of developing RGCs and raise the question of whether the survival control mechanisms of PNS and CNS neurons are different.