title: P23H rhodopsin transgenic rat: correlation of retinal function with histopathology.
abstract: OBJECTIVE
  To correlate retinal functional changes with structural changes in P23H rhodopsin transgenic rats as a model of autosomal dominant retinitis pigmentosa.
  
  
  METHODS
  P23H heterozygote (lines 1 and 3) and Sprague-Dawley control rats were studied at 4 to 29 weeks by retinal histology, electroretinogram (ERG), and a-wave transduction modeling.
  
  
  RESULTS
  Both line 1 (faster degeneration) and line 3 (slower degeneration) showed progressive rod outer segment (ROS) shortening and outer nuclear layer (ONL) cell loss with age. ERG b-wave maximum amplitude (Vb(max)) decreased with age, but b-wave threshold remained constant within each line despite progressive ONL thinning and ROS shortening. The only exception was in line 1 at 29 weeks, which showed a slight threshold change relative to earlier ages. Va(max) and a-wave threshold changed more rapidly and were more sensitive than the b-wave in reflecting histologic degeneration. Va(max) was linearly proportional to the product of (ROS x ONL) across a two log unit range of data combined from both lines. The photopic b-wave was normal for both lines until the ONL thinned beyond 50%. Phototransduction sensitivity was normal for both lines, and dark-adaptation recovery after bleaching rhodopsin was normal.
  
  
  CONCLUSIONS
  The P23H transgenic rat has a slow rod degeneration with initially normal cone function, consistent with clinical findings of P23H patients. However, the normal bleach recovery and the normal phototransduction sensitivity in this rat model are different from human P23H disease. a-Wave measures were more sensitive than the b-wave for tracking changes. b-Wave threshold was inexplicably poor for tracking degeneration. Although line 1 degenerated faster than line 3, the functional-structural correlates were the same. The tight linear relationship between saturated a-wave amplitude and the product of (ROS x ONL) indicates that the density of cGMP-gated channels per unit ROS plasma membrane area remains constant over a wide range of degenerations.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor 48105, USA.
authors.forename: S
authors.initials: S
authors.lastname: Machida
authors.forename: M
authors.initials: M
authors.lastname: Kondo
authors.forename: J A
authors.initials: JA
authors.lastname: Jamison
authors.forename: N W
authors.initials: NW
authors.lastname: Khan
authors.forename: L T
authors.initials: LT
authors.lastname: Kononen
authors.forename: T
authors.initials: T
authors.lastname: Sugawara
authors.forename: R A
authors.initials: RA
authors.lastname: Bush
authors.forename: P A
authors.initials: PA
authors.lastname: Sieving
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D008297:Male; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000473:pathology / Q000503:physiopathology*; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000473:pathology* / Q000503:physiopathology; D012243:Rhodopsin / Q000235:genetics*; D014785:Vision, Ocular
chemical_list: D012243:Rhodopsin