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 [mu]M) 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.(Received June 6 2000)
(Accepted November 13 2000)
Key Words: Kainate; AMPA; Electroretinogram; Xenopus; Excitotoxicity.
c1 Address correspondence and reprint requests to: Paul Witkovsky, Department of Ophthalmology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA. E-mail: firstname.lastname@example.org