Contributions of AMPA- and kainate-sensitive receptors to the photopic electroretinogram of the Xenopus retina.
The effects of kainate receptor-preferring glutamate ligands were tested on the electroretinogram (ERG) of the Xenopus retina. Kainate, domoic acid, and 5-iodowillardiine (20-100 microM) acted similarly in every respect. They increased peak amplitudes of the ERG a-, b-, and d-waves significantly over controls. The AMPA-specific antagonist, GYKI 53655, prevented a kainate-induced increase in ERG a- and d-waves, but was without effect on an increase in the b-wave. Once the effect of agonist on the b-wave had peaked, the ERG began to subside, leading to its nearly complete disappearance within 20 min. Prior exposure to GYKI followed by a combination of GYKI + agonist did not significantly slow the rate of b-wave disappearance. Our results indicate that (1) AMPA receptors contribute to ERG a- and d-waves. (2) The kainate-evoked increase in ERG a-, b-, and d-waves probably results, in part, from an excitotoxic swelling of inner retinal processes. (3) The inner retina has a population of GYKI-resistant, kainate-sensitive receptors which may contribute to b-wave generation.
Szikra
T
T
Department of Neurobiology and Physiology, Eotvos Lorand University, Budapest, Hungary.
Witkovsky
P
P
D000409:Alanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001569:Benzodiazepines / Q000494:pharmacology; D004596:Electroretinography / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008027:Light; D008297:Male; D011743:Pyrimidines / Q000494:pharmacology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000502:physiology*; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000502:physiology*; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D014982:Xenopus laevis
D000409:Alanine; D001569:Benzodiazepines; D018691:Excitatory Amino Acid Antagonists; D007608:Kainic Acid; D011743:Pyrimidines; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; C112482:5-iodowillardiine; C079692:GYKI 53655; C012301:domoic acid