Related Experiment Video
Updated: May 24, 2026

Cut-loading: A Useful Tool for Examining the Extent of Gap Junction Tracer Coupling Between Retinal Neurons
Published on: January 12, 2012
Gap-junctional coupling of mammalian rod photoreceptors and its effect on visual detection
Peter H Li1, Jan Verweij, James H Long
1Departments of Ophthalmology and Physiology, University of California, San Francisco, California 94143, USA.
Abstract:
The presence of gap junctions between rods in mammalian retina suggests a role for rod-rod coupling in human vision. Rod coupling is known to reduce response variability, but because junctional conductances are not known, the downstream effects on visual performance are uncertain. Here we assessed rod coupling in guinea pig retina by measuring: (1) the variability in responses to dim flashes, (2) Neurobiotin tracer coupling, and (3) junctional conductances. Results were consolidated into an electrical network model and a model of human psychophysical detection. Guinea pig rods form tracer pools of 1 to ∼20 rods, with junctional conductances averaging ∼350 pS. We calculate that coupling will reduce human dark-adapted sensitivity ∼10% by impairing the noise filtering of the synapse between rods and rod bipolar cells. However, coupling also mitigates synaptic saturation and is thus calculated to improve sensitivity when stimuli are spatially restricted or are superimposed over background illumination.
Related Concept Videos
Photoreceptors and Visual Pathways
Photoreceptors and Plant Responses to Light
Anatomy of the Eyeball
The Retina
Channel Rhodopsins
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
G-Protein Gated Ion Channels
Sensory organs,...

