Contribution of Kir4.1 to the mouse electroretinogram

[摘要] Purpose: The electroretinogram (ERG) represents the combination ofseveral distinct cellular processes and conductances. Here, we definethe contribution that K+ conductance through Kir4.1 channels makesto the mouse ERG.Methods: To obtain mice expressing different levels of Kir4.1, wemated Kir4.1+/- mice and used PCR to identifyKir4.1+/- and Kir4.1+/+ littermates. In addition, wemated Kir4.1+/- males with females homozygous for the nob(no b-wave) defect, which eliminates post-receptoral contributions tothe ERG. After overnight dark adaptation, mice were anesthetized andERGs were recorded to 7 min stimuli, to focus on slow ERG components, orto 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 inKir4.1+/- mice than in Kir4.1+/+ littermates. Incomparison, the amplitude of the light peak, the other main componentgenerated by the retinal pigment epithelium in response to light, didnot differ between Kir4.1+/- and Kir4.1+/+ mice. Theamplitude of slow PIII, revealed by the nob genetic background, wasreduced in Kir4.1+/- mice.Conclusions: These results indicate that a cornea-negativepotential, generated by Kir4.1, normally opposes a positive polarityconductance that is generated by the apical membrane of the retinalpigment epithelium to form the c-wave measured at the corneal surface.

[学科分类] 生物化学/生物物理