ON-OFF amacrine cells in cat retina

Abstract

We studied the morphology, photic responses, and synaptic connections of ON-OFF amacrine cells in the cat retina by penetrating them with intracellular electrodes, staining them with horseradish peroxidase, and examining them with the electron microscope. In a sample of seven cells, we found two different morphological types: the A19, which ramifies narrowly in stratum 2 (sublamina a) of the inner plexiform layer, and the A22, which ramifies mostly in stratum 4 (sublamina b) but extends some dendrites to sublamina a. Both of these cell types have axon-like processes that extend > 800 microns from the conventional dendritic arbor. ON-OFF amacrine cells in our sample had receptive fields (1.7 +/- 0.3 mm diameter) that were broader than their dendritic arbors (425 +/- 35 microns diameter) and that extended over the region of axon-like processes. In addition, we found many features in common with ON-OFF amacrine cells in poikilotherm vertebrates: a broad receptive field without surround antagonism, two sizes of spike-like events, narrow dynamic range (1 log unit intensity), and excitatory postsynaptic potentials at light on and light off. Two A19 amacrine cells were examined in the electron microscope: most synaptic inputs (93 and 76%, respectively) to either cell were from amacrine cells, with minor inputs from cone bipolar cells. Synaptic outputs were to bipolar, amacrine, and ganglion cells, including the OFF-alpha cell.

Inputs Underlying the ON–OFF Light Responses of Type 2 Wide-Field Amacrine Cells in TH::GFP Mice

“…4 D). These data suggest that type 2 cells possess receptive fields without surround antagonism and that excitatory inputs are distributed homogeneously along type 2 cell dendrites, as was shown for other ON-OFF WFA cells before (Freed et al, 1996;Bloomfield and Völgyi, 2007). Moreover, these results indicate that type 2 cells, even though their dendrites are large, must be electronically compact if an annulus located on their more peripheral dendritic field can produce a response that is almost identical to a spot that covers the central part of the dendritic field.…”

“…3A). Most ON-OFF amacrine cells show spikes in response to light stimuli (Freed et al, 1996;Stafford and Dacey, 1997;Bloomfield and Völgyi, 2007). However, for type 2 cells, we never observed spikes riding on top of the depolarization.…”

A model of high-frequency oscillatory potentials in retinal ganglion cells

“…Long-range connections were made exclusive by the axon-bearing amacrine cells. Consistent with the three amacrine cell types included in the model, the amacrine cells presynaptic to cat alpha ganglion cells include small types, possibly the A2, A3, A8, and AII amacrine cells, larger types, possibly the A13 and starburst amacrine cells, and axon-bearing types, probably the A19-22 amacrine cells (Kolb & Nelson, 1985Vardi et al, 1989;Freed et al, 1996;Owczarzak & Pourcho, 1999). In the cat retina, approximately 80% of all synapses onto alpha ganglion cells are from amacrine cells (Freed & Sterling, 1988;Owczarzak & Pourcho, 1999), consistent with the major contribution made by the model amacrine cells to ganglion cell light responses.…”

Functional polarity of dendrites and axons of primate A1 amacrine cells

“…This is in agreement with the A1 surround having an effect primarily on the area of the response, not the peak voltage. Receptive fields larger than dendritic fields have been used as an argument that axons could be providing input to axon-bearing amacrine cells (Freed et al, 1996). This may be a misinterpretation based on a failure to appreciate the influence of the surround.…”