The Role Of Voltage-gated Calcium Channel α2δ-1 In The Occurrence And Development In Myofascial Orofacial Pain

Objective:Patients who suffer from myofascial orofacial pain could have complications,such as anxiety,depression and sleep disorders,which affects the quality of life of patients deeply.The pathogenesis of pain is still unclear,and there is no definite treatment method to relieve it.voltage-gated calcium channelα₂δ-1（Cavα2δ-1）is a subunit of voltage-gated calcium channels,which participates in the assembly of calcium channels on the cell surface and regulates the biophysical properties of the channels.Existing studies have shown that the up-regulation of Cavα2δ-1 expression is related to the occurrence and development of neuropathic pain.In neuropathic pain models,such as spinal cord injury pain model,sciatic nerve ligation pain model and infraorbital nerve injury model,the expression levels of Cavα2δ-1 mRNA and protein in damaged neurons increase,which are related to the occurrence and development of allodynia.Meanwhile,in myofascial orofacial pain,whether Cavα2δ-1 is related to the occurrence and development of pain has not yet been reported.Therefore,in this study,experiments of establishing myofascial orofacial pain model in vivo and experiments on PC12 neuron cell lines in vitro were used to clarify the role of Cavα2δ-1 in the occurrence and development in myofascial orofacial pain.Materials and methods:In this study,ligation of the superficial tendon of the rat masseter muscle was used as the animal model.Twelve male rats were randomly divided into the masseter tendon ligation group and the sham group,each with 6 rats.The calibrated Von Frey sensory tester was used to measure the mechanical pain threshold of the masseter tendon ligation group and the sham operation group before operation,the 4th,7th,10th and 14th day after operation.On the 14th day after operation,Quantitative Real-time polymerase chain reaction（q RT-PCR）was used to measure the mRNA expression levels of Cavα2δ-1 in trigeminal ganglion,the trigeminal spinal subnucleus caudalis and C1-C2 spinal cervical dorsal horn（Vc/C₂）of the masseter tendon ligation group and the sham group.Eighteen male rats were randomly divided into Cavα2δ-1 antisense oligonucleotides group,Cavα2δ-1mismatched oligonucleotides group and normal saline control group,each with 6 rats.On the 4th day after ligating the superficial tendon of the left masseter muscle of the rats,10ul Cavα2δ-1 antisense oligonucleotide was injected into the left masseter muscle of rats in Cavα2δ-1 antisense oligonucleotide group twice a day for 4 days;10ul Cavα2δ-1 mismatched oligonucleotides was injected into the left masseter muscle of rats in Cavα2δ-1 mismatched oligonucleotides group twice a day for 4 days.10ul normal saline was injected into the left masseter muscle of rats in normal saline control group twice a day for 4 day.The calibrated Von Frey sensory tester was used to measure the mechanical pain threshold of Cavα2δ-1 antisense oligonucleotides group,Cavα2δ-1 mismatched oligonucleotides group and normal saline control group before operation,the 4th,7th,10th and 14th day after operation.q RT-PCR was used to detect the mRNA expression levels of Cavα2δ-1 in Lipopolysaccharides-injured PC12 cells.Results:The results of animal behavior experiments showed that compared with the sham group,the mechanical pain threshold of the masseter tendon ligation group was significantly reduced on the 4th,7th,10th and 14th day after operation（P<0.05）.Cavα2δ-1 mRNA expression levels in the trigeminal ganglion of the masseter tendon ligation group were increased on the 14th postoperative day（P=0.021）.Cavα2δ-1mRNA expression levels in the Vc/C₂tissue of the masseter tendon ligation group were increased on the 14th postoperative day（P=0.012）.The mechanical pain threshold of the Cavα2δ-1 antisense oligonucleotides group was higher than Cavα2δ-1mismatched oligonucleotides group on the 7th and 10th day after operation（P<0.01）.Cytology in vitro experiments showed that after PC12 cells were treated with lipopolysaccharide,the expression levels of Cavα2δ-1 mRNA increased（P<0.001）.Conclusion:The results of this study preliminarily indicate that Cavα2δ-1 may be involved in the occurrence and development in myofascial orofacial pain.