Long-term survival effects of GDNF on neonatal rat facial motoneurons after axotomy

Glial cell-line derived neurotrophic factor (GDNF) has survival promoting effects on axotomized neonatal motoneurons. We examined how long it could sustain motoneurons after postnatal day O (PND) facial nerve axotomy. GDNF, or cytochrome c as a negative control, were locally administered by Gelfoam implants at the time of axotomy and some were re-implanted on PND 14. The surviving motoneurons were quantified on PND 14 and 28. GDNF completely rescued lesioned motoneurons from axotomy-induced cell death at 14 days and was still effective (about 40%) at PND 28. GDNF also prevented axotomy-induced atrophy at both PND 14 and 28, indicating that the neurotrophic effects of GDNF on neonatal motoneurons are long-term.