CYCLIC-AMP ELEVATION IS SUFFICIENT TO PROMOTE THE SURVIVAL OF SPINAL MOTOR-NEURONS IN-VITRO

The short-term survival of highly purified embryonic spinal motor neur ons (SMNs) in culture can be promoted by many peptide trophic factors, including brain-derived neurotrophic factor (BDNF), ciliary neurotrop hic factor (CNTF), fibroblast growth factor (FGF), glial-derived neuro trophic factor (GDNF), and hepatocyte growth factor (HGF). We have ask ed whether these peptides are sufficient to promote the long-term surv ival of purified E15 SMNs. Contrary to previous reports, we find that when SMNs are cultured in serum-free medium containing a single peptid e trophic factor only approximately one-third of the cells survive for 3 d in culture. When multiple factors are combined, additive effects on survival are observed transiently, but by 7 d of culture the majori ty of SMNs has died. Surprisingly, when cAMP levels are elevated, the majority of SMNs extend processes and survive for 1 week in culture in the absence of peptide trophic factors, even in low-density cultures. A combination of five peptide trophic factors, together with cAMP ele vation, promotes the long-term survival of most of the SMNs in serum-f ree culture for 3 weeks. These findings provide useful culture conditi ons for studying the properties of SMNs and have implications for the treatment of motor neuron diseases.