Morphometric analysis of nNOS and eNOS. Box plots of the optical densities from morphometric measurements of nNOS (A) and eNOS (B) in the control NBA (in white box) and experimental HBO treatment group (in dash box). The expression of nNOS was significantly enhanced in nerve fiber bundles after HBOT. The expression of eNOS was significantly enhanced in the limbus, nerve fiber bundles and modiolar blood vessels after HBOT. The dots represent the outliers. OD, optical densities; SL, spiral ligament; SV, stria vascularis; OG, organ of Corti.