Effect of lappaconitine on neuropathic pain mediated by retrograde transport of P2X3 receptor in dorsal root ganglion neurons of rats with chronic constriction injury of the sciatic nerve / 中华创伤杂志

ABSTRACT

Objective:To investigate the effect of lappaconitine (LA) on neuropathic pain (NPP) mediated by retrograde transport of purinergic P2X3 receptor (P2X3R) in dorsal root ganglion (DRG) neurons of rats with chronic constriction injury (CCI) of the sciatic nerve.Methods:Seventy-two male healthy SD rats were selected to construct the NPP model following CCI of the sciatic nerve by ligating the right sciatic nerve. according to the random number table method. The rats were divided into CCI group, CCI+LA group and normal control group according to the random number table method, with 24 rats in each group. In normal control group, the right sciatic nerve was exposed without ligation. In CCI+LA group, the rats were given 2 g/L LA (ie, 4 mg/kg intravenously for once a day for one day only) after the same treatment as CCI group. Other two groups were injected with the identical amount of normal saline in the same way. The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were evaluated before injury and at 2, 6, 12 and 24 hours after injury to evaluate the symptoms of neuralgia caused by nerve injury. The proximal and distal nerve fragments were collected in the three groups at 2, 6, 12 and 24 hours after injury. Western blotting was applied to analyze the expression of P2X3R at 2, 6, 12 and 24 hours after injury and the expression of neurotrophic factor (NGF) and tyrosine kinase receptor A (TrkA) at 24 hours after injury to evaluate the effect of LA on P2X3R, NGF and TrkA.Results:There were insignificant differences in MWT and TWL among all groups before injury (all P>0.05). Compared with normal control group, MWT and TWL were significantly decreased in CCI group and CCI+LA group at 2, 6, 12 and 24 hours after injury (all P<0.05 or 0.01). There were insignificant differences in MWT and TWL between CCI group and CCI+LA group at 2 and 6 hours after injury (all P>0.05), while MWT and TWL were significantly higher in CCI+LA group than those in CCI group at 12 and 24 hours after injury (all P<0.05 or 0.01). In the proximal sciatic nerve segment, Western blotting showed similar levels of P2X3R among all groups at 2, 6, 12 and 24 hours after injury (all P>0.05). In the distal sciatic nerve segment, Western blotting showed higher expression of P2X3R in CCI group than that in normal control group at 2, 6, 12, 24 hours after injury (all P<0.01), higher expression of P2X3R in CCI+LA group than that in normal control group at 2, 6 and 12 hours after injury (all P<0.05), similar expression of P2X3R expression between CCI+LA group and normal control group at 24 hours after injury ( P>0.05), similar expression of P2X3R between CCI group and CCI+LA group at 2 and 6 hours after injury (all P>0.05), and lower expression of P2X3R in CCI+LA group than that in CCI group at 12 and 24 hours after injury ( P<0.05 or 0.01). In the proximal and distal nerve fragments, the expression of NGF was lower in normal control group than that in CCI group and CCI+LA group ( P<0.05 or 0.01), but was similar between CCI group and CCI+LA group at 24 hours after injury ( P>0.05). In the proximal and distal nerve fragments, there were insignificant differences in the expression of TrkA among all groups at 24 hours after injury (all P>0.05). Conclusion:Early LA treatment after injury can alleviate mechanical and thermal hyperalgesia in NPP rats, which may be related to the reduction of P2X3R retrograde transport in DRG neuron axonal.