Fig. 6: Glutamate causes ribbon swelling but not synapse degeneration.

One cochlea was incubated in NES with 0.2 mM glutamate for 2 h and another cochlea of the same mouse was simultaneously incubated with NES as control. Dashed lines connected two same symbols represent data collected from two cochleas of the same animal. N is the number of mice. a Glutamate has no significant effect on IHC ribbon, GluR, and synapse degeneration. The numbers of ribbon, GluR, and synapse per IHC were pooled from all cochlear turns and averaged and normalized to those in the control cochlea of the same mouse. P = 0.30–0.42, paired t-test, two-tail. b There are no significant ribbon degenerations in the different cochlear turns for glutamate challenge. The ribbon numbers per IHC in the different cochlear turns were normalized to those in the control cochlea of the same mouse. P = 0.45–0.91, paired t-test, two-tail. c, d Glutamate-induced IHC ribbon swelling. d Immunofluorescence staining for CtBP2 at the middle cochlear turn area in the glutamate-treated group and control group. IHC ribbons in the glutamate treated cochlea appear enlarged. Scale bar: 10 µm. **P < 0.01, paired t-test, two-tail.