Ciliary neurotrophic factor as a motor neuron trophic factor.

The survival of developing motor neurons has long been known to depend on contact with target muscle. This observation caused an intensive search for motor neuron trophic factors. During that search, a surprisingly large number of factors, including neurotrophins, glia-derived neurotrophic factor, fibroblast growth factors, and ciliary neurotrophic factor (CNTF) were found to promote motor neuron survival in vitro. The present review article examines in detail the evidence concerning the potential motor neuron trophic role of CNTF in vivo. The main conclusion of the article is that CNTF likely functions as a maintenance and repair factor for adult motor neurons and is less likely to play a significant developmental role. In addition, the article reviews the literature concerning the use of CNTF for treating motor neuron diseases and possible side effects of such treatment.