Influence of picrotoxin and strychnine on the spectral sensitivity of the turtle ERG b- and d-wave: I. Dark adaptation.
The ERG ON- (b-wave) and OFF-response (d-wave) to differently coloured stimuli was studied using a wide range of stimulus intensities in dark adapted turtle retina. The intensity-response curve of the b-wave showed saturation but that of the d-wave, decline in the high-intensity stimulus range. The curves of the relative spectral sensitivity of the ERG ON- and OFF-response were similar and showed a maximum in the longwave part of the spectrum. GABAergic blockade by 50 mumol L-1 picrotoxin caused an increase of the sensitivity, contrast sensitivity and the amplitude range of both ON- and OFF-responses without narrowing of the response dynamic range. In the range of lower stimulus intensities the ON-responses to blue stimuli and the OFF-responses to red stimuli were affected to a greater extent. An increased ERG b- and d-wave sensitivity was also observed during glycinergic blockade by 50 mumol L-1 strychnine. In the low intensity stimulus range the effect was maximal on the ON-response to blue stimuli and on the OFF-responses to 570 nm stimuli. It was concluded that the GABA- and glycinergic systems in the retina equalize rather than make different the relative spectral sensitivities of the ON- and OFF-responses.
Kupenova
P
P
Department of Physiology, Medical Faculty-Sofia, Bulgaria.
Vitanova
L
L
Popova
E
E
Mitova
L
L
D000818:Animals; D003118:Color Perception / Q000187:drug effects / Q000502:physiology; D003623:Dark Adaptation / Q000187:drug effects* / Q000502:physiology; D004585:Electrooculography; D018756:GABA Antagonists / Q000494:pharmacology*; D018684:Glycine Agents / Q000494:pharmacology*; D010852:Picrotoxin / Q000494:pharmacology*; D012160:Retina / Q000502:physiology; D012680:Sensitivity and Specificity; D013331:Strychnine / Q000494:pharmacology*; D014426:Turtles
D018756:GABA Antagonists; D018684:Glycine Agents; D010852:Picrotoxin; D013331:Strychnine