Figure 2.
Noise-induced demyelination and disruption of paranodal axoglial junctions. a, b, Normal type I (I) SGNs and their myelinating glial cells in an adult CBA/CaJ mouse. The panel to the right of b shows enlargements of the boxed areas in b. The top image shows compact myelin lamellae (white arrowheads), and the bottom image shows paranodal axo-glial junctions (black arrowheads). c–f, One day after 106 dB SPL noise exposure for 2 h, the compact lamellae of myelin sheaths are disrupted. c–f, Disruption of the myelin sheath surrounding neurons, often with large separations (black arrowhead in c, asterisks in d and e, white arrowhead in f) and disruption of axo-glial junctions (black arrowhead in f). The panel to the right of f contains enlarged images of the boxed areas in f. g, h, k, Fourteen days (D14) after noise exposure, demyelination of SGNs was associated with numerous myelin whorls and cytoplasmic vacuolization (black arrows in g and k, and white arrow in h). At D14, a typical type I SGN was seen ensheathed by a single layer of satellite glial cell cytoplasm lacking myelin (i) as occurs in type II (II) neurons of the control AN (j). l, At D30, most glial cells ensheathing type I SGNs have lost their compact myelin lamellae (black arrows). m, A reduction (arrows) and eventual loss (arrowheads) of NrCAM+ nodal structures were seen in the habenula at D1 after 112 dB SPL noise exposure. n, The percentage of SGNs with abnormal myelin sheaths was greatly increased at D1 after 106 dB SPL exposure. o, Delayed wave I latencies were present at 11.3, 16, and 32 kHz at D3 after 106 dB SPL noise exposure (*p < 0.05 and **p < 0.01, Mann–Whitney test; Figure 2-1, exact statistical output). Data are presented as the mean ± SEM. Scale bars: a, d, 3 μm; b, c, f, g, k, l, 800 nm; e, i, j, 2 μm; h, 5 μm; m, 4 μm.