LEUKEMIA INHIBITORY FACTOR PREVENTS THE DEATH OF AXOTOMISED SENSORY NEURONS IN THE DORSAL-ROOT GANGLIA OF THE NEONATAL RAT

Leukemia inhibitory factor (LIF) has several characteristics of a neur otrophic factor for sensory neurons. Here we have investigated whether LIF also supports the survival of axotomised sensory neurons in vivo. Newborn rat pups received a unilateral sciatic nerve transection and the injury site was treated with gelfoam soaked in phosphate buffered saline (PBS), nerve growth factor (NGF), or LIF. Neuronal nucleoli in the L5 dorsal root ganglia were counted, appropriate corrections appli ed, and the resultant neuronal loss expressed as a percentage of the c ontralateral intact side. In animals where LIF was administered neuron al loss was significantly reduced: 2 days after LIF treatment neuronal loss was 19.5% compared to 43% in PBS-treated animals; 3 days after L IF treatment neuronal loss was 20.4% compared to 40.2% in PBS-treated animals; however, 7 days after LIF treatment there was no significant reduction in the number of neurons lost. The degree of rescue of senso ry neurons in vivo by LIF was found to be similar to NGF, which was no t surprising as both factors supported the survival of a similar popul ation of sensory neurons in vitro. Rescue was not observed when LIF-co ntaining gelfoam was placed away from the axotomised nerve, suggesting that LIF's action may be associated with its retrograde transport or direct signalling at the site of nerve injury. (C) 1994 Wiley-Liss, In c.