Figure 4.

Monaural conductive hearing loss enlarges the postsynaptic membrane of auditory nerve synapses on bushy cells. A, Drawings of an auditory nerve (AN) synapse on a bushy cell (BC) showing how the thickness of the PSD was calculated. B, Representative PSD diagrams of the sham, earplug, and postearplug-removal groups that were obtained from the 3D reconstructions of serial ultrathin sections. Scale bar, 50 nm. C, Plot showing a significant increase in the mean PSD area of the synapse of the auditory nerve on bushy cells after earplug removal (sham P40, 0.036 ± 0.003 μm²; earplugged P40, 0.045 ± 0.005 μm²; **p = 0.02, Mann–Whitney U test; sham P50, 0.037 ± 0.004 μm²; earplug-removal P50, 0.058 ± 0.005 μm²; p = 0.0006, Mann–Whitney U test). Error bars are ±SEM. D, Plot showing a significant increase in the average PSD thickness during earplug and after 10 d of earplug removal (sham P40, 26.21 ± 0.88 nm; earplugged P40, 41.72 ± 1.72 nm; ****p < 0.0001, Mann–Whitney U test; sham P50, 25.47 ± 1.56 nm; earplug-removal P50, 43.28 ± 1.793 nm; ****p < 0.0001, Mann–Whitney U test). Error bars are ±SEM.