Functional allocation of synaptic contacts in microcircuits from rods via rod bipolar to AII amacrine cells in the mouse retina.
Bottom Line: In more detail, over 50% of each RB output was directed predominantly to a single, preferred AII amacrine cell, although each RB cell also separately contacted another one to three AII amacrine cells.Thus the original signal may be reliably represented by signal amplification with focal accumulation without gathering unnecessary noise from a wide surrounding area.This allocation of RB-AII synaptic contacts may serve as the structural basis for the physiological properties of the AII single-photon response that include high amplification, local adaptation, and regenerative acceleration.
Affiliation: Studio Retina, Satonaka, Nishinomiya, Hyogo, 663-8183, Japan; Department of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, 663-8501, Japan.Show MeSH
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Mentions: AII 3 collected rod-driven signals from 174 rods through nine (eight completely and one incompletely reconstructed) RB cells, as shown in Figure 3. The number of rods converging on each RB cell ranged from 24 to 27, with an average of 25 (25 ± 1, n = 8), except for RB15 in the upper left of Figure 3 (for which only 15 rods were identified because of the end of the series). Each of the 41 rods (23.6%) contacted a pair of invaginating dendrites of different RB cells among the nine RB cells connected to AII 3. Each of the 124 rods contacted one invaginating dendrite extending from one of the nine RB cells and with another invaginating dendrite (not shown in Fig. 3) extending from an RB cell outside these nine RB cells (122 rods, 70.1%) or a type 7 On cone bipolar cell (two rods, 1.1%; Tsukamoto et al, 2007). Three other rods (1.7%) contacted a pair of invaginating dendrites branching from a proximal RB dendrite outside the spherule, and each of the remaining six rods (3.4%) contacted a Y-shaped RB invaginating dendrite that bifurcated within the spherule. Thus, most of the rods (93.7%) diverged to two RB cells, but a small number (6.3%) of rods diverged to one RB cell, yielding an average divergence of 1.94.
Affiliation: Studio Retina, Satonaka, Nishinomiya, Hyogo, 663-8183, Japan; Department of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, 663-8501, Japan.