Table 1.
Synaptic ribbon properties in gerbil hair cells
| Immature OHCs (3rd row) | Immature IHCs | Adult IHCs | ||||
|---|---|---|---|---|---|---|
| Apical | Basal | Apical | Basal | Apical | Basal | |
| Ca2+ dependence of exocytosis (power N) | 0.7 | 1.1 | 3.6 | 3.9 | 2.2 | 1.0 |
| Ribbon no. | 18 | 22 | 36 | 37 | 21 | 22 |
| Vesicles in the total RRP | 135 | 143 | 400 | 510 | 534 | 619 |
| RRP vesicles per ribbon | 8 | 7 | 11 | 14 | 26 | 28 |
| RRP release rate (vesicles s−1) | — | — | 12 911 | 13 425 | 10 449 | 14 883 |
| RRP release rate per ribbon (vesicles s−1) | — | — | 355 | 360 | 507 | 664 |
| SRP release rate (vesicles s−1) | — | — | 8208 | 7933 | 2335 | 1695 |
| SRP release rate per ribbon (vesicles s−1) | — | — | 216 | 214 | 111 | 77 |
| SRP depletion time constant (s) | — | — | 8.6 | 4.8 | 12.0 | 21.3 |
All numbers reported are mean values. s.e.m. and cell numbers for immature data are given in Results. Adult values are obtained or calculated from Johnson et al. 2008. For immature OHCs, recording were only performed from the outer row (3rd row) of cells. The ribbon number and RRP vesicles per ribbon in immature OHCs are based on the estimation of two ribbons per active zone (see Results). OHC exocytotic kinetics were not measured. We did not observe any RRP depletion in both immature and adult IHCs using 50 ms voltage steps (at about 7 Hz).