Visual Neuroscience



Contributions of AMPA- and kainate-sensitive receptors to the photopic electroretinogram of the Xenopus retina


T.  SZIKRA a1a2 and P.  WITKOVSKY a2a3c1
a1 MTA-ELTE Neurobiology Group, Department of Neurobiology and Physiology, Eotvos Lorand University, Budapest, Hungary
a2 Department of Ophthalmology, New York University School of Medicine, New York
a3 Department of Physiology and Neuroscience, New York University School of Medicine, New York

Abstract

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.

Correspondence:
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: pw20@nyu.edu