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N.S. Garina, V.G. Erchenkov; Cone Contribution to the Tectal Light Evoked Potentials in the Dark Adapted Carp . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5377.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate rod and cone contributions to the tectal evoked potentials and to the b–wave ERG, which reflect activity to light on–set of presynaptic and, respectively, postsynaptic to retinal ganglion cells neurons.
Evoked potentials (EP) in the carp optic tectum and ERG to monochromatic light stimuli (stimulus duration 1 ms) were simultaneously registered in the darkness. Light wave length might be changed from 404 nm to 680 nm (step =20 nm), light intensity might be decreased (step=0,2 log. unit) by density filters in 3 log. unit diapason (5x1012 – 5x109q/mm2x sec). Amplitude and time to pike were measured for the first postsynaptic component of tectal EP to light on–set as well as for b–wave ERG.
The action spectra for tectal EP displayed three relatively flat peaks (in short– middle–and long–wave areas) and differed from the action spectra for b–wave ERG, which had only one peak (in the middle wave area). Action spectra for both responses were the same for all light intensities. The intensity–response curves from tectal EP and from b–wave ERG were also different. Tectal EP amplitude growth was found when light intensity increased from –3,0 log to –1,8 log. Brighter light (–1, 8 – 0, 0 log) did not change EP amplitude. The b–wave amplitude increased in all intensity diapason. So, the dynamic range of the tectal EP was smaller (1,2±0,6 log) than that in the b–wave ERG (2,0±0,4 lg). Time to peak in the both responses decreased when light intensity increased. This decreasing was stronger for tectal EP (100–200 ms), than for b–wave ERG (50–100 ms). Amplitude and time to peak changes did not depend on the light wave length.
Results suggest that rod retinal system determines the b–wave generation in dark–adapted conditions, but it does not dominate in tectal EP to light on–set. So, cone contribution becomes more prominent in the postsynaptic to ganglion cell neurons
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