title: The effect of picrotoxin on the absolute and increment retinal sensitivity.
abstract: The aim of this study was to investigate the influence of the GABAergic inhibitory neurones on the absolute and increment retinal sensitivity, determined be measuring b-wave threshold of frog electroretinogram (ERG). We found that GABAergic blockade by picrotoxin (PT -noncompetitive GABA antagonist) had no apparent effect on the absolute (dark adapted) b-wave threshold (12 microV criterion amplitude) and slightly, but significantly lowered its increment threshold under both levels of background illumination (0.25 lx and 200 lx), used in this study. A similar effect to that observed in light-adapted eyes was also seen in dark-adapted eyes when suprathreshold stimulus intensities, giving 25 microV b-wave amplitude were presented. Another observation was marked increase of the d-wave amplitude after PT both in dark and light-adapted eyes. We suggest that the different photoreceptor input to the GABAergic interneurones and neurones, responsible for b-wave generation is the cause for the different PT effect on the absolute (rod mediated) and increment (predominantly cone mediated) b-wave threshold of frog ERG. The possible role of the GABAergic inhibitory neurones in the process of light adaptation is discussed.
authors.affiliation: Department of Physiology, Medico-Biological Institute, Medical Academy, Sofia, Bulgaria.
authors.forename: E
authors.initials: E
authors.lastname: Popova
mesh_terms: D000818:Animals; D004596:Electroretinography; D066298:In Vitro Techniques; D010852:Picrotoxin / Q000494:pharmacology*; D011895:Rana ridibunda; D012160:Retina / Q000187:drug effects*
chemical_list: D010852:Picrotoxin