Objective To evalute the effects of subcutaneous transfection of human beta-nerve growth factor (Ad-hNGFβ) gene on the function of sensory nerve in a rat model of diabetic neuropathic pain (DNP).Methods Healthy male Sprague-Dawley rats,weighing 180-220 g,were used in this study.Ten rats were randomly collected as normal control without DNP (group C).DNP model was established by intraperitoneal injection of streptozocin (STZ) 75 mg/kg.Seventy-five rats with DNP were randomly divided into 3 groups (n =25 each):DNP group; Ad-hNGF group and Ad-LacZ group.Groups Ad-NGF and Ad-LacZ received subcutaneous transfection of 1.12 × 1011 PFU Ad-hNGFβ 10 ul and 1.12 × 1011 PFU Ad-LacZ 10 ul respectively after pain thresholds were measured on 21 days after STZ injection.The mechanical and thermal pain thresholds were measured before STZ injection (baseline) and at 21,35 and 49 days after STZ injection.The conduction velocity and latency of the sensory nerve and the expression of substance P (SP) in dorsal root ganglion (by immmuno-histpchemistry) were determined after measurement of pain threshold on 49 days after STZ injection.Results Compared with group C,the mechanical and thermal pain thresholds were significantly increased at each time point after STZ injection in groups DNP,Ad-NGF and Ad-Lacz,the conduction velocity of the sensory nerve was significantly decreased,the latency of the sensory nerve was prolonged,and the expression of SP in dorsal root ganglion was down-regulated in groups DNP and Ad-LacZ,the conduction velocity of the sensory nerve was significantly decreased (P ＜ 0.05),and no significant change was found in the latency of the sensory nerve and expression of SP in dorsal root ganglion in group Ad-NGF (P ＞ 0.05).Compared with group DNP,the thermal pain threshold was significantly increased at 49 days after STZ injection,the conduction velocity of the sensory nerve was decreased,the latency of the sensory nerve was shortened,and the expression of SP in dorsal root ganglion was down-regulated (P ＜ 0.05 or 0.01),while no significant change was found in the mechanical pain threshold in group Ad-NGF,and no significant change was found in the parameters mentioned above in group Ad-LacZ (P ＞ 0.05).Conclusion Subcutaneous transfection of Ad-hNGFβ can improve the function of sensory nerve in a rat model of DNP through up-regulat-ing of the SP expression in dorsal root ganglion.