Contribution of Kir4.1 to the mouse electroretinogram.
OBJECTIVE
The electroretinogram (ERG) represents the combination of several distinct cellular processes and conductances. Here, we define the contribution that K+ conductance through Kir4.1 channels makes to the mouse ERG.


METHODS
To obtain mice expressing different levels of Kir4.1, we mated Kir4.1+/- mice and used PCR to identify Kir4.1+/- and Kir4.1+/+ littermates. In addition, we mated Kir4.1+/- males with females homozygous for the nob (no b-wave) defect, which eliminates post-receptoral contributions to the ERG. After overnight dark adaptation, mice were anesthetized and ERGs were recorded to 7 min stimuli, to focus on slow ERG components, or to strobe flash stimuli, to examine earlier ERG components.


RESULTS
The amplitudes of the ERG c-wave and the fast oscillation, measured from the c-wave peak, were significantly larger in Kir4.1+/- mice than in Kir4.1+/+ littermates. In comparison, the amplitude of the light peak, the other main component generated by the retinal pigment epithelium in response to light, did not differ between Kir4.1+/- and Kir4.1+/+ mice. The amplitude of slow PIII, revealed by the nob genetic background, was reduced in Kir4.1+/- mice.


CONCLUSIONS
These results indicate that a cornea-negative potential, generated by Kir4.1, normally opposes a positive polarity conductance that is generated by the apical membrane of the retinal pigment epithelium to form the c-wave measured at the corneal surface.
Wu
Jiang
J
Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA. peachen@ccf.org
Marmorstein
Alan D
AD
Kofuji
Paulo
P
Peachey
Neal S
NS
D000818:Animals; D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D010775:Photic Stimulation; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D012160:Retina / Q000502:physiology*
D024661:Potassium Channels, Inwardly Rectifying; D011188:Potassium