DESENSITIZATION OF THE GABA(A) RECEPTOR SHIFTS THE DYNAMIC-RANGE OF RETINAL HORIZONTAL CELLS DUE TO LIGHT AND DARK-ADAPTATION

The effects of the GABAergic pathway on the dynamic range of the light response of cone-driven horizontal cells (HCs) in the carp retina wer e investigated using conventional intracellular recordings and compute r simulations. The amplitude of the HC responses to repetitive test fl ashes was altered by background illumination in control Ringer's solut ion, but was not changed following the application of picrotoxin or bi cuculline, which suggests that GABAA 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.