title: Photoreceptor and post-photoreceptoral contributions to photopic ERG a-wave in rhodopsin P347L transgenic rabbits.
abstract: OBJECTIVE
  The a-wave of the photopic electroretinogram (ERG) of macaque monkeys is made up of the electrical activities of cone photoreceptors and post-photoreceptoral neurons. However, it is not known whether the contributions of these two components change in retinas with inherited photoreceptor degeneration. The purpose of this study was to determine the contributions of cones and post-photoreceptoral neurons to the a-wave of the photopic ERGs in rhodopsin Pro347Leu transgenic (Tg) rabbits.
  
  
  METHODS
  Ten Tg and 10 wild-type (WT) New Zealand White rabbits were studied at 4 and 12 months of age. The a-waves of the photopic ERGs were elicited by xenon flashes of different stimulus strengths before and after the activities of post-photoreceptoral neurons were blocked by intravitreal injections of a combination of 0.2 to 0.4 mM of 6-cyano-7-nitrouinoxaline-2,3(1H,4H)-dione, disodium (CNQX) and 2 to 4 mM of (±)-2-amino-4-phosphonobutyric acid.
  
  
  RESULTS
  The percentage contribution of the cone photoreceptors to the photopic ERG a-waves increased with increasing stimulus strength, and the percentage ranged from 54% to 75% in 4-month-old WT rabbits. In contrast, the percentage contribution of the cone photoreceptors in 4-month-old Tg rabbits ranged from 32% to 51% (P < 0.05). The mean percentage contribution of cone photoreceptors became still smaller at 11% to 48% in 12-month-old Tg rabbits.
  
  
  CONCLUSIONS
  These results suggest that the relative contribution of cone photoreceptors to the photopic ERG a-wave is smaller in retinas with inherited photoreceptor degeneration. This indicates that the a-waves of the photopic ERGs in patients with retinitis pigmentosa must consider this lower contribution from the cone photoreceptors.
authors.affiliation: Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Hirota
authors.forename: Mineo
authors.initials: M
authors.lastname: Kondo
authors.forename: Shinji
authors.initials: S
authors.lastname: Ueno
authors.forename: Takao
authors.initials: T
authors.lastname: Sakai
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Koyasu
authors.forename: Hiroko
authors.initials: H
authors.lastname: Terasaki
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004195:Disease Models, Animal; D004596:Electroretinography / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007395:Interneurons / Q000502:physiology*; D058449:Intravitreal Injections; D011817:Rabbits; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012243:Rhodopsin / Q000235:genetics*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018698:Glutamic Acid; D012243:Rhodopsin