Objective To investigate the effects of lactoferrin on activity of PKG in spinal dorsal horn in a rat model of neuropathic pain(NP).Methods Thirty-two male SD rats weighing 200-250 g were randomly divided into4 groups(n = 8 each): sham operation group(group S),NP group,lactoferrin group and KT5823(an inhibitor of PKG)group.Neuropathic pain was produced by placing loosely constrictive ligatures around the common sciatic nerve in group NP,lactoferrin and KT5823,while the sciatic nerve was only exposed but not ligated in groupS.In group S and NP,normal saline 10 μl + 50% dimethyl sulfoxide(DMSO)10 μl were injected intrathecally.Lactoferrin 100 μg + 50% DMSO 10 μl were given intrathecally in group lactoferrin.Lactoferrin 100 μg + KT5823 10 μl were given intrathecally in group KT5823.The paw withdrawal latency(PWL)to a thermal nociceptive stimulus was measured every 30 min within 180 min after administration.The rats were then sacrificed and the spinal cord was removed.The activity of PKG in the spinal dorsal horn was determined by immunofluorescence.Results Compared with group NP and KT5823,the PWL was significantly prolonged after administration in group lactoferrin and the PKG activity was significantly increased in group lactoferrin(P ＜ 0.05).There was no significant difference in the parameters mentioned above between group NP and group KT5823(P ＞ 0.05).Conclusion Lactoferrin reduces NP by inhibiting the activity of PKG in spinal dorsal horn in rats.