Contribution of voltage-gated sodium channels to b- and d-waves of frog electroretinogram under different conditions of light adaptation.
The effect of blockade of voltage-gated sodium (Na(v)) channels by tetrodotoxin (TTX) on the V-log I function of the ERG b- and d-waves was investigated in light and dark adapted frog eyecups. TTX diminished the b- and d-wave amplitude under both conditions of adaptation at all stimulus intensities except for the middle intensity range in dark adapted eyes, where it had no effect on the b-wave amplitude. TTX delayed the time course of the responses, obtained with low intensity stimuli and widened the dynamic range of the b-wave. The inhibitory effect of TTX on the cone-mediated, but not rod-mediated b- and d-wave amplitude persisted after the blockade of proximal retinal activity by NMDA, indicating that it may be due to a blockade of Na(v) channels on the ON and OFF bipolar cells.
Popova
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Department of Physiology, Medical Faculty, Medical University, 1431 Sofia, Bulgaria. epopova@abv.bg
Kupenova
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D000221:Adaptation, Ocular / Q000502:physiology*; D000818:Animals; D001001:Anura; D003623:Dark Adaptation / Q000502:physiology; D004596:Electroretinography / Q000379:methods; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin