N-Methyl-D-Aspartate Receptors Involvement in the Gentamicin-Induced Hearing Loss and Pathological Changes of Ribbon Synapse in the Mouse Cochlear Inner Hair Cells

Figure 8

The 3D-reconstructed images and numerical data for the ribbon pairs after different treatments. Afferent synapses on IHCs are seen by immunostaining presynaptic ribbons with anti-CtBP2 (green) and postsynaptic AMPARs with anti-GluA2 (red). Nuclei were labeled with DAPI (blue). (a, b, c) In the study, we define the “IHC basal pole region” and the “IHC nuclei region” in every single IHC. The changed tendency in location of AMPARs and ribbons was observed around the IHC in the 3D-reconstructed images. (a) Ribbons and AMPARs were paired at the basal poles of the IHCs in the control cochlea. (b) After gentamicin treatment for 4 days, the presynaptic ribbons and postsynaptic AMPARs were relocated towards the bundle poles of the IHCs. The number of ribbons and AMPARs was decreased at the basal pole of IHCs. (c) After combined treatment with gentamicin and MK801 for 4 days, most of the IHC ribbons and postsynaptic AMPARs remained at the basal poles of the IHCs, but a few AMPARs were still observed near the IHC nuclei region. (d) The number of ribbon synaptic pairs among the control group, gentamicin treatment group for 4 days, and combined treatment group with gentamicin and MK801 for 4 days. (e) The number of ribbon synaptic pairs among the control group, gentamicin treatment group for 7 days, and combined treatment group with gentamicin and MK801 for 7 days. GM 4 d, 7 d: gentamicin treatment for 4 days or 7 days; GM + MK 4d, 7d: combined treatment with gentamicin and MK801 for 4 days or 7 days; IHC: inner hair cell .