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C. Mora-Ferrer, V. M. Vergin, M. Loser; The Contribution of the ON-Channel to Full-Filed Motion Perception in Goldfish Under Scotopic and Mesopic Illumination Conditions. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3859.
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Full-field motion perception (FF-MP) is independent of ambient illumination, i.e. scotopic, mesopic or photopic conditions. Either rods or cones feed, through ON-bipolar cells (ON-BC) via mGluR6, rods, or EAAT5, cones, ON-DS-GC which have been associated with full-field motion coding (FF-MC). The relative contribution of rods and cones to the ON-channel was investigated behaviorally under scotopic, mesopic and photopic illumination conditions.
FF-MP was quantified using the optomotor response which was elicited with a rotating black-white sine-wave modulated (80-100% mod. depth) full-field stimulus. Animals were adapted 10-30 minutes prior testing. Light stimuli used were either "white" light (photopic) or light of 540 and 640 nm wavelength and different light intensities (mesopic/scotopic). Transmission via mGluR6 was impaired with L-AP4 (intra-ocular concentration in microM: 100) and through EAAT5 with TBOA (1-10.
Photopic conditions: TBOA reduced the FF-MP by up to 30%. Mesopic conditions: In average, animals were 0.6 log unitsmore sensitive to light of 640 nm than to light of 540 nm wavelength. TBOA shifted these threshold intensities by 0.6-0.7 log units to higher intensities. L-AP4 reduced the optomotor response by 50% or more. Scotopic conditions: Animals were about 0.5 log units more sensitive to light of 540 nm than 640 nm wavelength. TBOA increased the optomotor response to low light intensities by up to 50% but had no effect at higher light intensities. L-AP4 nearly eliminated the optomotor response to light of 540 nm.
In photopic illumination conditions L-AP4 does not affect high contrast FF-MP and TBOA reduces high contrast FF-MP. Under mesopic illumination conditions the FF-MP is rod dominated with an additional L-cone input. The relative inputs vary with the stimulus light intensities. Blockade of EAATs does not result in a general disruption of retinal processing. Under scotopic illumination conditions L-AP4 eliminates FF-MP indicating that at least for directional coding class III metabotropic Glu-receptors are essential. TBOA did not impair FF-MP and thus not FF-MC. This indicates that the contribution of the rod- and cone-driven ON-channel can be investigated independently under different illumination conditions.
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