CILIARY NEUROTROPHIC FACTOR STIMULATES NEURITE OUTGROWTH FROM SPINAL-CORD NEURONS

Ciliary neurotrophic factor (CNTF) has been shown to promote the survi val of motoneurons, but its effects on axonal outgrowth have not been examined in detail. Since nerve growth factor (NGF) promotes the outgr owth of neurites within the same populations of neurons that depend on NGF for survival, we investigated whether CNTF would stimulate neurit e outgrowth from motoneurons in addition to enhancing their survival. We found that CNTF is a powerful promoter of neurite outgrowth from cu ltured chick embryo ventral spinal cord neurons. An effect of CNTF on neurite outgrowth was detectable within 7 hours, and at a concentratio n of 10 ng/ml, CNTF enhanced neurite length by about 3- to 4-fold with in 48 hours. The neurite growth-promoting effect of CNTF does not appe ar to be a consequence of its survival-promoting effect. To determine whether the effect of CNTF on spinal cord neurons was specific for mot oneurons, we analyzed cell survival and neurite outgrowth for motoneur ons labeled with diI, as well as for neurons taken from the dorsal hal f of the spinal cord, which lacks motoneurons. We found that the effec t of CNTF was about the same for motoneurons as it was for neurons fro m the dorsal spinal cord. The responsiveness of a variety of spinal co rd neurons to CNTF may broaden the appeal of CNTF as a candidate for t he treatment of spinal cord injury or disease. (C) 1996 Wiley-Liss, In c.