CILIARY NEUROTROPHIC FACTOR PROMOTES THE SURVIVAL OF SPINAL SENSORY NEURONS FOLLOWING AXOTOMY BUT NOT DURING THE PERIOD OF PROGRAMMED CELL-DEATH

We have examined the in vivo survival effect of ciliary neurotrophic f actor (CNTF) on sensory, i.e., dorsal root ganglion (DRG) neurons duri ng the period of naturally occurring (programmed) cell death and follo wing axotomy in the developing chick and mouse. Administration of CNTF during the period of naturally occurring cell death, from Embryonic D ay (E) 6 to E10 in the chick and E14 to E18 in the mouse, had no signi ficant effect in preventing the death of DRG neurons in either species . Axotomy on E12 in the chick or on Postnatal Day (PN) 5 in the mouse resulted in a 60% and a 33% decrease, respectively, in ipsilateral DRG neuron numbers by E16 (chick) or by PN12 (mouse), when compared to co ntralateral controls. CNTF treatment prevented axotomy-induced cell de ath of DRG neurons in both the chick and mouse. Daily administration o f CNTF following axotomy in E12 chicks significantly increased (72%) D RG neurons by E16. Similarly, CNTF completely rescued mouse DRG neuron s from axotomy-induced death. These results show that although CNTF ha s no effect on naturally occurring death of chick or mouse sensory neu rons, this agent has significant ability to rescue sensory neurons fol lowing axotomy. These findings suggest that CNTF may be an effective t herapeutic agent for the prevention of injury-induced death of vertebr ate sensory neurons. (C) 1995 Academic Press, Inc.