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Sign‐preserving and sign‐inverting synaptic interactions between rod and cone photoreceptors in the dark‐adapted retina
Author(s) -
Gao Fan,
Pang JiJie,
Wu Samuel M.
Publication year - 2013
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2013.260984
Subject(s) - retina , biophysics , anatomy , coupling (piping) , cone (formal languages) , rod , physics , chemistry , neuroscience , biology , optics , materials science , mathematics , medicine , alternative medicine , algorithm , pathology , metallurgy
Key points• Five types of rods and cones in the dark‐adapted salamander retina are electrically coupled with linear and symmetrical junctional conductances G j of different average values. • The average G j values of the five types of rod–cone pairs recorded at day and night times suggest that the the circadian‐dependent changes in rod–cone coupling observed in the fish and rodent retinas are not present in the tiger salamander. • In addition to rod–cone coupling, there is a sign‐inverting, unidirectional rod→cone current I RC , and the current–voltage ( I RC –V Cone ) relations are linear, with a reversal potential near the chloride reversal potential E Cl . • I RC can be observed in rods and cones separated by at least 260 μm, and its waveform resembles that of the rod‐elicited horizontal cell (HC) response I HC ; a glutamate transporter‐associated chloride channel blocker TBOA suppresses I RC without affecting I HC . • These results suggest that I RC is largely mediated by HCs via a sign‐inverting feedback chemical synapse associated with a chloride channel in cones.Abstract We show that various types of rods and cones in the dark‐adapted salamander retina are electrically coupled with linear and symmetrical junctional conductances G j (40–223 pS) and a rank order: Rod C –large single cone, rod–large single cone, rod–small single cone, rod–accessory double cone and rod–principal double cone. By systematically comparing the transjunctional current–voltage ( I j –V j ) relations and average G j values of the five types of rod–cone pairs recorded at day and night times, our results suggest that the differences in G j values among various types of rod–cone pairs are not caused by circadian differences, and the circadian‐dependent changes in rod–cone coupling observed in the fish and rodent retinas are not present in the tiger salamander. In addition to rod–cone coupling, there is a sign‐inverting, unidirectional rod→cone current I RC , and the I RC –V Cone relations are linear, with a reversal potential near the chloride reversal potential E Cl . I RC can be observed in rods and cones separated by at least 260 μm, and its waveform resembles that of the rod‐elicited horizontal cell (HC) response I HC . A glutamate transporter‐associated chloride channel blocker TBOA suppresses I RC but not I HC . These results suggest that I RC is largely mediated by HCs via a sign‐inverting feedback chemical synapse associated with a chloride channel. I RC significantly reduced rod→cone coupling in the frequency range below 15 Hz, allowing better separation of rod and cone signals in the dark‐adapted retina.