Objective To examine the effect of intrathecal administration of nerve growth factor (NGF)on healing of tibial shaft fracture in rats. Methotis Forty-eight adult male SD rats were randomized into 2 equal groups.In the experiment group,2.5 S mNGF was injected into the intrathecal space at the L1 level of spinal cord for 2 weeks(1 μg/day),while the control were treated with normal saline of the same amount.After injection,the animals in both groups were sacrificed respectively at days 7,14,21 and 28 for all X-ray evaluation on the bone callus and an immunohistochemistry assay on related dorsal root ganglia (DRG)and osteotylus. Results The immunoreactivity of calcitonin gene-related peptide(CGRP)and substance P(SP)in DRG and osteotylus was significantly hisher in the NGF group than in the saline-treated controls.X-ray CValuation of osteotylus 21 to 28 days after fracture scored lower in the NGF group than in the controls but the healing process was enhanced in the former.A hisher proportion of cartilage was found in the NGF group than in the controls,and the reconstruction of callus was promoted. Conclusion Stimulating the release of sensory neuropeptides in the rat spinal cord and enhancing the immunoreactivity of CGRP and SP in DRG and callus.NGF Can result in accelerated fracture healing.