Figure 2. New contacts between hair cells and spiral ganglion neurons appear in co-culture and express AMPA receptors.

A-C, Representative examples of live co-cultures at DIV10-11 showing Bhlhb5^Cre/+; Ai9^fl/+, td-Tomato expressing SGN endings (red) close to ChR2⁺ hair cells (green). In A and B, several IHCs are contacted by multiple endings from a single SGN. Arrowheads in A and C point to a SGN soma. In C, SGN fiber travels along the row of IHCs. Arrow points to a SGN projection reaching the OHC region. D, Confocal maximum-intensity projection image from an immuno-labeled co-culture at DIV 12. The insets show individual labels and overlay at a single synapse, with presynaptic ribbon (Anti-CtBP2; red) juxtaposed with postsynaptic AMPA receptors (Anti-PAN GluA1-4; blue). Anti-Myosin VI (orange) labels hair cells and Anti-NF200 (white) labels nerve fibers.