Fig. 6.

Histogram showing the tangential distribution of gold particles (15 nm) representing GluR2/3 (A) and GluR4 (B) in the postsynaptic membrane of inner hair cell synapses. Zero is defined as the point opposite the center of the synaptic body. The tangential extent of the synapse was set at 100%, and the synaptic body was localized at 50.9 ± 6.3% (mean ± SD,n = 25), i.e., near the middle of the synapse. Only synapses with distinct synaptic bodies cut at their approximate centers were included in the analysis (13 synapses for GluR2/3 and 12 for GluR4). Bin width, 50 nm. Values along the x-axis indicate centers of bins. Gold particles were omitted if situated >28 nm away from the cytoplasmic aspect of the postsynaptic membrane, i.e., particles, which according to Figure 7, could not represent postsynaptic receptors with a localization corresponding to the position of the peak in Figure 5A. The distance (mean ± SD, n = 25) between the synaptic body and the lateralmost gold particle was 196 ± 64 nm (maximum 301 nm) compared with a radius of the postsynaptic density of 260 ± 44 nm (range 157–382).