Surround antagonism in macaque cone photoreceptors.
Center-surround antagonism is a hallmark feature of the receptive fields of sensory neurons. In retinas of lower vertebrates, surround antagonism derives in part from inhibition of cone photoreceptors by horizontal cells. Using whole-cell patch recording methods, we found that light-evoked responses of cones in macaque monkey were antagonized when surrounding cones were illuminated. The spatial and spectral properties of this antagonism indicate that it results from inhibition by horizontal cells. It has been suggested that horizontal cell inhibition is mediated by the neurotransmitter GABA. The inhibition observed here, however, was inconsistent with a GABA-gated chloride conductance mechanism. Instead, surround illumination evoked an increase in calcium conductance and calcium-activated chloride conductance in cones. We expect that these conductances modulate neurotransmitter release at the cone synapse and increase visual sensitivity to spatial contrast.
Verweij
Jan
J
Department of Ophthalmology, University of California, San Francisco, California 94143-0730, USA.
Hornstein
Eric P
EP
Schnapf
Julie L
JL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D008252:Macaca fascicularis / Q000502:physiology*; D008253:Macaca mulatta / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation / Q000379:methods; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology
D015220:Calcium Channels; D018118:Chloride Channels; D002712:Chlorides; D018691:Excitatory Amino Acid Antagonists; D003035:Cobalt; D005680:gamma-Aminobutyric Acid; C018021:cobaltous chloride; D002118:Calcium