The present invention is directed to novel peptides and compositions capableof modulating viability and growth inneuronal cells, and to methods of modulating neuronal cell viability andgrowth employing the novel peptides and compositions ofthe invention. In one aspect, the invention is directed to novel peptideanalogues of motoneuronotrophic factor 1 containing either a"WMLSAFS" or "FSRYAR domain," which is sufficient for neurotrophic orneurotropic function.