The Variation Of NPR-A Receptor Expression On Mouse Trigeminal Ganglion Neurons Of Trigeminal Neuralgia Model

Objective To establish two trigeminal neuralgia models of adult male rat, that is injecting TNF-α, a kind of inflammatory cytokines, through infraorbital foramen around infraorbital nerve and chronic constriction injury of the rat’s infraorbital nerve. To evaluate the changes of natriuretic peptide receptor(NPR)-A expression in rat trigeminal ganglion neurons of rat trigeminal neuralgia models with the behavior and molecular biology technology, such as RT-PCR, Western Blot.Methods Male SD rats were randomly assigned into six groups: control group 1(sham group), control group 2(infraorbital foramen inject normal saline group), chronic constriction injury of the infraorbital nerve guoup(ION-CCI group) 1 week and 2weeks and infraorbital foramen inject TNF-α group(TNF-α group) 1 week and 2 weeks.The mechanical withdrawal threshold of vibrissa pad was detected and documented every week postoperatively to ensure the establishment of trigeminal neuralgia in rat models.Total RNA and protein of the trigeminal ganglion were extracted at each time point.Real-time PCR and Western-blot were performed to measure the expression of NPR-A in each group and explore the relationship between NPR-A and trigeminal neuralgia.Results At 1 week after ION-CCI, the rats showed significantly increased responsiveness to mechanical stimulation of the territory of the ligated nerve(from16.66±1.59 g reduce to 7.90 ± 1.34 g). At the second week after ION-CCI, the pain threshold fell to the lowest(4.22 ±1.06 g), and lasting until at least 8 weeks postoperatively(9.17±1.66 g), which was statistically significant difference compared with that in the control group(F = 74.32, 282.59, n = 5, P < 0.01).In the TNF-α-1w group, the mechanical pain threshold of the rats was decreasedfrom 16.65 ± 1.69 g to 5.86 ± 1.23 g and fell to the lowest(3.66 ±1.26 g) at 2 weeks postoperatively, which was statistically difference compared with that in the saline group(F = 103.04, 123.16, n = 5, P < 0.01).The mechanical pain threshold of the rats in TNF-α was gradually increased and recovered to preoperative levels at 8 weeks postoperatively(14.61 ± 1.85 g). No significant change of the pain threshold was observed in the control groups.The rat model of trigeminal neuralgia was established successfully by injecting TNF-α through infraorbital foramen around infraorbital nerve and chronic constriction injury of the rat’s infraorbital nerve. The m RNA expression of NPR-A receptor and NPR-A protein were detected in rat trigeminal neuralgia models. The NPR-A receptor m RNA and NPR-A protein were expressed much more in the ION-CCI-2w and TNF-αgroup than those in the control groups(P < 0.05).Conclusions The NPR-A receptor may influence the occurrence and the advancement of the trigeminal neuralgia in two models of the trigeminal neuralgia of rats.