title: Flash responses of mouse rod photoreceptors in the isolated retina and corneal electroretinogram: comparison of gain and kinetics.
abstract: OBJECTIVE
  To examine the amplification and kinetics of murine rod photoresponses by recording ERG flash responses in vivo and ex vivo from the same retina. We also aimed to evaluate the two available methods for isolating the rod signal from the ERG flash response, that is, pharmacology and paired flash method on the isolated retina.
  
  
  METHODS
  Dark-adapted ERG responses to full-field flashes of green light were recorded from anesthetized (ketamine/xylazine) C57BL/6N mice. ERG flash responses to homogenous light stimuli arriving from the photoreceptor side were then recorded transretinally from the same retinas, isolated and perfused with Ringer's or Ames' solution at 37°C. The responses were analyzed to determine the a-wave kinetics as well as the estimated flash sensitivity and kinetics of the full rod responses derived with the paired flash protocol. The analysis was complemented with pharmacologic blockade of glutamatergic transmission in the isolated retina.
  
  
  RESULTS
  The a-waves were of comparable size, sensitivity and kinetics in vivo and in the isolated retina, but the onset of the b-wave was delayed in the isolated retina. The Lamb-Pugh activation constants determined for the a-waves were similar in both preparations. The kinetics of the derived photoreceptor responses were similar in both conditions, although the responses were consistently slightly slower ex vivo. This was not explicable as a direct effect of ketamine or xylazine on the photoreceptors or as their indirect effect through hyperglycemia, as tested on the isolated retina.
  
  
  CONCLUSIONS
  Through comparison to the corneal ERG, the transretinal ERG is a valuable tool for assaying the physiologic state of isolated retinal tissue. The rod photoreceptor responses of the intact isolated retina correspond well to those recorded in vivo. The origin of their faster kinetics compared to single cell recordings remains to be determined.
authors: Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Aalto, Finland. hanna.heikkinen@aalto.fi
authors: Hanna
authors: H
authors: Heikkinen
authors: Frans
authors: F
authors: Vinberg
authors: Marja
authors: M
authors: Pitkänen
authors: Bertel
authors: B
authors: Kommonen
authors: Ari
authors: A
authors: Koskelainen
mesh_terms: D000613:Aminobutyrates / Q000494:pharmacology; D000778:Anesthetics, Dissociative / Q000494:pharmacology; D000818:Animals; D017609:Barium Compounds / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003315:Cornea / Q000502:physiology*; D003623:Dark Adaptation / Q000502:physiology; D004596:Electroretinography / Q000187:drug effects / Q000379:methods*; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007649:Ketamine / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009924:Organ Culture Techniques; D010775:Photic Stimulation / Q000379:methods; D055213:Retinal Pigment Epithelium / Q000502:physiology; D012168:Retinal Pigments / Q000502:physiology; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000502:physiology*; D014991:Xylazine / Q000494:pharmacology
chemical_list: D000613:Aminobutyrates; D000778:Anesthetics, Dissociative; D017609:Barium Compounds; D002712:Chlorides; D006993:Hypnotics and Sedatives; D012168:Retinal Pigments; C024986:barium chloride; D014991:Xylazine; D007649:Ketamine; C012729:2-amino-4-phosphonobutyric acid