| Objective The rat model of trigeminal neuralgia (TN) was made to detect the reaction with mechanical stimulation before and after surgery, and the change of the morphology and the histology in the trigeminal ganglion (TG) neurons. To investigate the dynamic changes of the P2X2and P2X3receptors in rat TG neurons after TN in order to seek for the variant role of P2X2and P2X3receptors and provide a new theoretical basis for the clinical treatment of TN.Methods90adult male SD rats were randomly divided into3groups.30rats were in the normal control group,30rats were in the model group, and30rats were in the sham group. They were detected at3time periods, and each period had10rats in each group. All of the rats were raised under the same condition. The normal control group did not do any treatment. The rats in model group and sham group were operated at1st,4th and8th week. The right infraorbital nerves were ligated to cause the chronic constriction injury to the infraorbital nerve (CCI-ION) model, and the sham group were only exposed the infraorbital nerves, but not ligated it. The rats of each group were decapitated and taken out the TGs at the end of the8th week. The TGs in the normal control group (Con group), model group (surgery side, S group; contralateral surgery side, D group) and sham group (J group) were detected with pain threshold test to appreciate the pain behavior of rat, the HE staining to evaluate modeling method, and immunohistochemistry and Western blot to measure the expression of the P2X2and P2X3receptors in different periods. All statistical analysis was performed using spss17.0software.Results1. Compared with the Con and J group, the pain threshold of the S group was decreased obviously from the1st week after surgery (P<0.001) and lasted for8weeks. Compared with the Con group, the pain threshold of the J group did not have significant changes which altered around15g (P>0.05), and the D group was decreased obviously from the4th week to the8th week after surgery (P<0.001).2. The TG nerve fibers of S group rats were demyelinated, circuity and fractured. The expressions of P2X2and P2X3receptors could be detectd in TG neurons of each group.3. Compared with the Con group, the expression of P2X2receptor in TG neurons of S group was significantly increased in the1st week and4th week after surgery (P<0.05), and was no significant change in the8th week (P>0.05) which had a slight higher than that in the Con group. However, the expression of P2X3receptor in TG neurons of S group was significantly increased in the1st,4th, and8th weeks (P<0.05) compared with the Con group. Compared with the Con group, the expression of P2X2receptor in TG neurons of D group was no obvious change in all periods after surgery (P>0.05), but the expression of P2X3receptor in TG neurons of D group was obviously increased in the8th week after surgery (P<0.05). Compared with the Con group, the expression of P2X2receptor in TG neurons of J group was obviously increased in the1st week (P<0.05), which recovered to Con group level in the4th and8th weeks (P>0.05), and the expression of P2X3receptor in TG neurons of J group was only obviously increased in the1st week after surgery (P<0.05). Compared with the D group, the expression of P2X2receptor in TG neurons of S group was no significant difference in each period after surgery (P>0.05), however, the expression of P2X3receptor in TG neurons of S group was significantly increased in each period after surgery (P<0.01). Compared with the J group, the expression of P2X2receptor in TG neurons of D group was slight enhancement in the4th week after surgery which did not had significant difference (P>0.05), but was significantly increased in the8th week, and the expression of P2X3receptor in TG neurons of D group was significant less in1st week after surgery (P<0.001), was no obvious change in the4th week (P>0.05), but was significantly increased in the8th week (P<0.05).Conclusion According to behavior and the dynamic changes of P2X2and P2X3receptors in the TG neurons of the rat CCI-ION model, we found that:1. CCI-ION method has many advantages, such as wider vision field for operation, clearer anatomical position, more completely nerve exposed, less bleeding and operated infection, which improve the success rate of modeling. After CCI-ION, the rats appear mechanical hyperalgesia responses, and pain characteristics are close to the clinical manifestations of TN. Thus this method can be used as a reliable method of TN model.2. Because pain thresholds of the S group rats reduce significantly and the expression of P2X2and P2X3receptors are increased in S group, the results suggest that P2X2and P2X3receptors are involved the pain induction and transmission of TN.3. The pain threshold of the J group does not change obviously, and the P2X2and P2X3receptor expressions increase significantly in the initial postoperative, but return to normal in the late period; The pain threshold of the D group reduces significantly in the late period, the expression of P2X2receptor in TG neurons of D group has no significant changes after treatment, but the expression of P2X3receptor in TG neurons of D group has significant enhancement. Those results indicate that P2X2receptor maybe primarily involved in acute pain or inflammatory pain, and P2X3receptor may play an importment role in acute pain and pain maintenance. |
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