Comparison of the responses of AII amacrine cells in the dark- and light-adapted rabbit retina

Vis Neurosci. Jul-Aug 1999;16(4):653-65. doi: 10.1017/s0952523899164058.

Abstract

We studied the light-evoked responses of AII amacrine cells in the rabbit retina under dark- and light-adapted conditions. In contrast to the results of previous studies, we found that AII cells display robust responses to light over a 6-7 log unit intensity range, well beyond the operating range of rod photoreceptors. Under dark adaptation, AII cells showed an ON-center/OFF-surround receptive-field organization. The intensity-response profile of the center-mediated response component followed a dual-limbed sigmoidal function indicating a transition from rod to cone mediation as stimulus intensities were increased. Following light adaptation, the receptive-field organization of AII cells changed dramatically. Light-adapted AII cells showed both ON- and OFF-responses to stimulation of the center receptive field, but we found no evidence for an antagonistic surround. Interestingly, the OFF-center response appeared first following rapid light adaptation and was then replaced gradually over a 1-4 min period by the emerging ON-center response component. Application of the metabotropic glutamate receptor agonist APB, the ionotropic glutamate blocker CNQX, 8-bromo-cGMP, and the nitric oxide donor SNAP all showed differential effects on the various center-mediated responses displayed by dark- and light-adapted AII cells. Taken together, these pharmacological results indicated that different synaptic circuits are responsible for the generation of the different AII cell responses. Specifically, the rod-driven ON-center responses are apparently derived from rod bipolar cell synaptic inputs, whereas the cone-driven ON-center responses arise from signals crossing the gap junctions between AII cells and ON-center cone bipolar cells. Additionally, the OFF-center response of light-adapted AII cells reflects direct synaptic inputs from OFF-center cone bipolar cells to AII dendritic processes in the distal inner plexiform layer.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
  • Adaptation, Ocular / physiology*
  • Aminobutyrates / pharmacology
  • Animals
  • Cyclic GMP / pharmacology
  • Dark Adaptation / physiology*
  • Electrophysiology
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Nitric Oxide Donors / pharmacology
  • Penicillamine / analogs & derivatives
  • Penicillamine / pharmacology
  • Rabbits
  • Retina / cytology*
  • Retina / drug effects
  • Retina / physiology*
  • S-Nitroso-N-Acetylpenicillamine

Substances

  • Aminobutyrates
  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • Nitric Oxide Donors
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • S-Nitroso-N-Acetylpenicillamine
  • Penicillamine
  • Cyclic GMP
  • 2-amino-4-phosphonobutyric acid