| ObjectiveBy using neuroethology and immunohistochemistry methods, we study the effect of Lornoxicam on the neurological behavior change and the expression of growth associated protein-43 (GAP-43) and nerve growth factor (NGF) in dorsal root ganglion on the peripheral nerve chronic constriction injury model of rats.MethodsFifty SD rats were randomly divided into four groups, group I: normal control rats; group II: sciatic nerve chronic constriction injury rats (CCI group); group III: Lornoxicam therapy after sciatic nerve chronic constriction injury rats (CCI+Lornoxicam group); group IV: physiologic saline therapy after sciatic nerve chronic constriction injury rats (CCI+NS group). Groups II, III, IV were subdivided equally into 3 groups according to the different postoperative interval: 3, 7 and 14 days (five rats each subgroup). The right sciatic nerve was injury only, and the left side was to be normal control. The dosage of Lornoxicam is 1.3mg/kg q12h. i.p.. Then, to measure the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of the rats of II, III and IV groups at the different postoperative interval: 3, 7 and 14 days. After that, the dorsal root ganglions to the chronic constriction injured sciatic nerves were harvested. Immunohistochemistry and image analysis were used to examine the expression of GAP-43 and NGF.ResultsMechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL):①Comparing with the normal group, the latencies of MWT and TWL at CCI, CCI+NS and CCI+Lornoxicam groups had a marked decline at the third, seventh and fourteenth day after surgery (P<0.01).②The differences in MWT and TWL between CCI and CCI+NS group was not statistically significant.③Comparing with the CCI+NS group, the MWT and TWL of CCI+Lornoxicam group had a significant increase at the same time point of the third, seventh and fourteenth day after surgery (P<0.01).The expression of GAP-43 and NGF in dorsal root ganglion:①Comparing with the normal group, the expression of GAP-43 and NGF of CCI group, CCI+NS group and CCI+Lornoxicam group had a remarkable increase after surgery (P<0.01).②The difference between CCI group and CCI+NS group was not statistically significant in the expression of GAP-43 and NGF.③Comparing with the CCI+NS group, the expression of GAP-43 and NGF of CCI+Lornoxicam group had a significant decline at the same time point after surgery (P<0.01).④The expression of GAP-43 at CCI group showed a gradually increase after surgery, and it reached the peak at the fourteenth day. The expression of NGF at CCI group increase markedly at the third day after surgery, and then fall gradually, however, it still kept a high level of expression (P<0.01 comparing with the normal group).Conclusions1. Cyclooxygenase inhibitor—Lornoxicam, 1.3mg/kg q12h i.p., could relieve the symptom of heat and mechanical hyperalgesia after sciatic nerve chronic constriction injury; it proved that lornoxicam is effective to the therapy of neuropathic pain. However, the dosage of lornoxicam used in this study could not completely inhibit the development of heat and mechanical hyperalgesia.2. GAP-43 and NGF have a closed relation with neuropathic pain. The expression of GAP-43 and NGF in the dorsal root ganglions in the neuropathic pain model of CCI had a markable increase comparing with the normal control. This suggests that GAP-43 and NGF may involve in the development of neuropathic pain.3. Using lornoxicam, 1.3mg/kg q12h, could effectively inhibit the high expression of GAP-43 and NGF to a low level in the dorsal root ganglions during the development of neuropathic pain, thus it could effectively inhibit the development of neuropathic pain. However, it could not suppress the expression of GAP-43 and NGF to normal level. To combined together the neurological behavior experiment, we can get a conclusion this dosage of lornoxicam could not reach the therapy effect of completely inhibit the neuropathic pain.
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