Research Of Cochlear Function And Morphology Of Mice With Selective SGN-expression Of Diphtheria Toxin Receptor

Objective: After DT injection,to investigate the functional and morphological change of cochlea,especially the pathological and physiological change of ribbon synapse,of mice with selective SGN-expression of diphtheria toxin receptor.Method: We adopted the offspring of the healthy mice of SGN specific expressed Cre and the of Cre-inducible homozygous DTR.We took the mice of which SGN expressed DTR as the experimental group,and the ones of which SGN did not express DTR as the control group.After DT injection intraperitoneally,we performed ABR,CAP,AM CAP response at 1,3,7,30 days post injection.After the test,wo investigate the morphological change of HC,SGN and ribbon synapse.Result: After the DT infection,there was no change of ABR threshold or HC.In the experimental group,the CAP amplitude and AM CAP response were significantly lower than the control(P<0.05).The SGN loss was 45%,and there was demyelination change in the auditory nerve.At 3days post injection,the pre-and post-membrane of ribbon synapse separated,and at 7 days post injection,the pre-and post-membrane of ribbon synapse re-matched,but the total number of ribbon synapse was 30% less,and the change remained to 30 days post injection.Conclusion: After DT injection,there were injury in the SGN and ribbon synapse but change of HC in the experimental group.And such mice suffered lesion of nerve dys-synchrony,but the hearing sensitivity of them was unchanged.So they might be applied as the model of human auditory neuropathy.