Figure 3.
(a, b) Synaptic ribbons (green) are contained in descending axons of calbindin-positive bipolar cells (red) that contact TOH-positive DACs (blue). (c) Ribbon synapses (green) in stratum 1 of sublamina a occur in apposition to the AMPA receptor marker anti-GluR4 (magenta). The lower panel of (c) shows that those ribbons (arrows) that appose TOH+ cells (blue) also contain the GluR4 marker. Ribbons not on TOH+ cells also appose GluR4-positive sites. (d–f) Synaptic ribbons sometimes occur (arrows) on the somas of DACs (blue). (d) These ribbons can occur at abutments of the somas of the amacrine cells with a calbindin-positive bipolar cell (red), (e) as the axon of the bipolar cell emanates from its soma and contacts the upper portion of the amacrine cell, or (f) as it contacts a lower portion of the soma again prior to entering the IPL. Scale bars (a) 1 µm; (b, c) 2 µm; (d–f) 10 µm. All panels consist of single 0.3 µm optical sections.