Effects of picrotoxin and strychnine on non‐linear responses of Y‐type cat retinal ganglion cells.

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Abstract
The effects of neurotransmitter antagonists on spatially linear and nonlinear responses of Y cat retinal ganglion cells were studied. The contrast sensitivity of the spatially linear receptive field center and surround at mesopic and photopic levels of illumination was affected very little by picrotoxin, but the sensitivity of the nonlinear subunits was reduced. Picrotoxin also reduced 2 other nonlinear effects: shift responses and the suppression of the response to a centered test flash caused by movement of a peripheral pattern. In contrast to picrotoxin, strychnine decreased the contrast sensitivity of the receptive field center and increased the sensitivity of the subunits. The nonlinear responses may all be generated by similar pathways, which are distinct from those which generate linear responses. Because both picrotoxin and strychnine affect subunit responses, cells using GABA and glycine as transmitters are probably involved in subunit pathways.