Fig. 4: DX-52-1-induced effects on OHC electromotility, lipid mobility, and microphonics.

a An OHC stereocilia bundle showing change in electrically evoked motility. Images acquired during negative current were encoded in green; images during positive current in red. b Time course of electromotility amplitude in an example preparation (blue circle) showing increase after DX-52-1 injection. The vertical line at time zero indicates the time of injection. Data were normalized to the average electromotility amplitude recorded before injection. c The average electromotility amplitude increased significantly after the DX-52-1 injection (n = 70) with no significant change after DMSO injection (n = 15). The acoustic stimulus was a 220 Hz tone at 80 dB with current stimulus of ±10 µA. d FRAP experiment showing lack of change in the stereocilia bundle morphology before and after DX-52-1 injection, except for a slight change in the dye intensity. e Normalized traces of the fluorescence intensity showing change in the membrane dynamics before and after DX-52-1 and DMSO injection in an example preparation. f Fitting the experimental data to single-phase exponential model showed a significantly faster recovery of bundle fluorescence with reduced τ_1/2 after DX-52-1 injection (n = 24) and with no change in the diffusion time after DMSO injection (n = 14). g No change in the cell somatic membrane morphology before and after DX-52-1 injection. h Normalized traces of the fluorescence intensity showing no change in the membrane dynamics before and after DX-52-1 and DMSO injection. i Fitting the experimental data to single-phase exponential fit model showed a non-significantly faster recovery of cell membrane fluorescence with reduced τ_1/2 after DX-52-1 (n = 16) injection and with no change in the diffusion time after DMSO injection (n = 12). Data are mean ± s.d. j Tuning curves for the cochlear microphonic (CM) potential before and after 1 mM DX-52-1 injection in an example preparation. k Example time courses of the peak amplitude of the CM potential which decreased substantially 10–15 min after DX-52-1 injection but not significantly after DMSO. The vertical line indicates the time of injection of DX-52-1 and DMSO. l Comparison of the average CM amplitude which reduced significantly before and after DX-52-1 injection (n = 40) but not after DMSO injection (n = 11) for experiments in panel (k). Data are mean ± s.d. A significant difference in the microphonic amplitude was observed between DX-52-1 and DMSO. All data sets were normalized to the data recorded before injection. ****P < 0.0001; ***P < 0.001; **P < 0.01; *P < 0.05; n.s., not significant; two-tailed paired t-test, two-tailed unpaired t-test with Welch’s correction.