(
A) Stratum-by-stratum rules for correlating patterns of axon terminal ramification and physiological responses in retinal bipolar cells. 22 morphologically identified (by Lucifer yellow filling) BCs and their light-evoked excitatory cation current (ΔI
C) and inhibitory chloride current (ΔI
Cl) recorded from dark-adapted salamander retinal slices. Each cell is named according to their spectral difference (ΔS) and ΔI
C polarity as rod-dominated, cone-dominated, mixed rod/cone hyperpolarizing or depolarizing bipolar cells (HBC
R, HBC
C, HBC
R/C, DBC
R, DBC
C or DBC
R/C). BCs with inward ΔI
C are DBCs and with outward ΔI
C are HBCs. The spectral difference, ΔS, is defined as S
700 − S
500 (where S
700 and S
500 are intensities in log units of 700- and 500-nm light eliciting responses of the same amplitude). Since ΔS for the salamander rods is approximately 3.4 and that for the cones is approximately 0.1, BCs with ΔS > 2.0 are rod-dominated (HBC
R or DBC
R), with ΔS < 1.0 are cone-dominated (HBC
C or DBC
C), and with 1.0 < ΔS < 2.0 are mixed rod/cone cells (HBC
R/C or DBC
R/C, also named HBC
M or DBC
M, see
Fig. 4). Displaced HBC
Cs: HBC
Cs with somas displaced in the outer nuclear layer. (Modified from Pang J-J, Gao F, Wu SM. Stratum-by-stratum projection of light response attributes by retinal bipolar cells of
Ambystoma. J. Physiol. 2004;558:249–262. © 2004 by The Physiological Society; and Maple BR, Zhang J, Pang J-J, Gao F, Wu SM. Characterization of displaced bipolar cells in the tiger salamander retina.
Vision Res. 2005;45:697–705. © 2005 Elsevier Ltd.) (
B) Schematic diagram of synaptic connections of photoreceptors, BCs, ACs, and α GCs in the mammalian retina. R, rod; MC, M-cone; SC, S-cone; HBC
MC/R, mixed M-cone/rod hyperpolarizing BC; HBC
MC, M-cone dominated hyperpolarizing bipolar cell; HBC
SC, S-cone dominated hyperpolarizing bipolar cell; DBC
C2, type 2 cone depolarizing bipolar cell; DBC
C1, type 1 cone depolarizing bipolar cell; DBC
R2, type 2 rod depolarizing bipolar cell; DBC
R1, type 1 rod depolarizing bipolar cell. Note that BCs with the most rod inputs have axon terminal endings near the two margins of the IPL, whereas those with the most cone inputs bear axons ramifying in the central regions of the IPL, similar to the rules set forward by the salamander BCs (
A). AC
M1, M-cone dominated depolarizing amacrine cell; AC
M2, M-cone dominated ON-OFF amacrine cell; AII, AII amacrine cell; A17/S1, A17 amacrine cell; sOFFαGC, sustained OFF αGC; tOFFαGC, transient OFF αGC; ONαGC, ON αGC;
green: rods and rod BCs;
blue: M-cones and M-cone BCs,
purple: S-cone and S-cone BCs;
light orange: GABAergic ACs;
dark orange: glycinergic ACs;
gray: αGCs;
arrows: chemical synapses (
red, glutamatergic;
black, GABAergic;
blue, glycinergic; +, sign-preserving; −, sign-inverting); zigzag (
red): electrical synapses. PRL, photoreceptor layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer (a, sublamina a, b, sublamina b); GCL, ganglion cell layer. Many inhibitory synapses from unspecified ACs are represented as
black and
blue arrows.