The Mechanisms For Differential Expression Of Nicotinic Acetylcholine Receptors In Facial Muscles And Limb Skeletal Muscles And The Changes After Facial Nerve Injury

Objective: To investigate the differential expression of nicotinic acetylcholine receptors in the facial nerve-innervated orbicularis and the somatic nerve-innervated gastrocnemius.To explore the expression changes and positional changes of the agrin/Lrp4/Mu SK/rapsyn and NRG1/Erb B pathways in the endplate of the orbicularis oris after facial nerve injury.Methods: 200-220 g SD rats were randomly divided into facial nerve injury group and normal facial nerve control group.The microvascular hemostasis was used to establish the facial nerve injury model,and the injured facial nerve-innervated orbicularis muscles were harvested at 1d,3d,7d,14 d,30d,60 d and 90 d after facial nerve injury.The orbicularis oris and gastrocnemius in normal group were taken out in the same way.The level of Mu SK phosphorylation in the gastrocnemius and orbicularis oris innervated by normal or facial nerve were calculated by immunoprecipitation.Immunofluorescence staining was used to investigate Mu SK,agrin,Lrp4,rapsyn,and epidermal growth factor family receptors Erb B2,Erb B3,and Erb B4 in the gastrocnemius and orbicularis oris in normal and injured groups.The expression and distribution of matrix metalloproteinase MMP3 in the endplate of the orbicularis oris were explored by immunofluorescence after facial nerve injury.Results: The level of Mu SK phosphorylation in the orbicularis oris muscle was significantly higher than that in the gastrocnemius muscle(P<0.05),but there was no significant difference in the expression of agrin,Mu SK and Lrp4(P>0.05).The expression of Erb B2,Erb B3 and Erb B4 in the orbicularis oris was significantly higher than that in the motor endplate of the gastrocnemius(P<0.01).The expression of agrin was significantly decreased after facial nerve injury,while the expression of Lrp4,Mu SK,rapsyn,Erb B and MMP3 in the endplate of the orbicularis oris was significantly increased.Conclusion: The different expressions of Erb B2,Erb B3,Erb B4 result the different level of phosphorylated Mu SK,which could contribute to the different expression of nicotinic acetylcholine receptors in facial nerve innervated orbicularis oris and somatic nerve innervated gastrocnemius.After the facial nerve injury,synaptic and extrasynaptic expression of Mu SK and rapsyn contribute to the upregulated expression of nicotinic acetylcholine receptors in facial nerve-innervated orbicularis oris.