GABAergic control on the intensity-response function of ERG waves under different background illumination.
The effect of GABAergic blockade on the intensity-response function of frog ERG waves was investigated under two levels of background illumination in the mesopic and photopic range. GABAergic blockade by picrotoxin shifted the intensity-response curves to the left along the intensity axis and increased their slope under both backgrounds. The maximal gain (dV/dI) and contrast gain (dV/dlog I) of the mechanisms responsible for the ERG wave generation were also increased after GABAergic blockade. The intensity range in which the amplitude of the response was a linear function of the logarithm of the stimulus intensity was very restricted. GABAergic blockade influenced also the rapid transitory processes, which determined the steady-state amplitude of the ERG b-wave after a considerable change of the stimulus contrast. The adaptational effect of the background illumination on the intensity-response function of the ERG waves was not principally changed after GABAergic blockade. The possible neuronal mechanisms of the observed picrotoxin effects are discussed.
Popova
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Department of Pathology, Medico-Biological Institute, Medical Academy, Sofia, Bulgaria.
Penchev
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A
D000818:Animals; D004596:Electroretinography; D010852:Picrotoxin; D011895:Rana ridibunda; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D010852:Picrotoxin; D005680:gamma-Aminobutyric Acid