The effects of the GABAergic pathway on the dynamic range of the light response of cone-driven horizontal cells (HCs) in the carp retina were investigated using conventional intracellular recordings and computer simulations. The amplitude of the HC responses to repetitive test flashes was altered by background illumination in control Ringer's solution, but was not changed following the application of picrotoxin or bicuculline, which suggests that GABA(A) receptors mediate the subsequent change in light response. This phenomenon was simulated by introducing the desensitization mechanism of the GABA(A) receptor into a cone-HC network model. These results suggest that desensitization of the GABA(A) receptor shifts the dynamic range of the HCs due to light and dark adaptation.
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