Analysis of electroretinogram during systemic hypercapnia with intraretinal K(+)-microelectrodes in cats.
OBJECTIVE
Systemic hypercapnia alters the intraretinal pH and metabolism and profoundly affects the vitreal electroretinogram (ERG). Using intraretinal K(+)-selective microelectrodes (ISMs), the authors examined the effects of systemic hypercapnia on ERG in the intact cat eye in vivo.


METHODS
Double-barreled K(+)-ISMs were used to record intraretinal, light-evoked [K+]o decrease, intraretinal ERG, vitreal ERG, and standing potential (SP) in the dark-adapted retina. Hypercapnia was induced by adding CO2 to the inhaled mixture of gas (without significant hypoxia).


RESULTS
The standing potential was elevated, and the vitreal ERG c-wave increased in amplitude whereas the b-wave decreased during hypercapnia. Intraretinal recordings showed that the amplitudes of slow PIII and the transepithelial (TEP) c-wave decreased. The slow PIII decreased more than the TEP c-wave. The light-evoked [K+]o decrease also was reduced, but no change was noted in the subretinal [K+]o.


CONCLUSIONS
The neural retina was more sensitive than the retinal pigment epithelium to the intraretinal acidification caused by systemic hypercapnia. However, the change in the SP and b-wave suggested complicated effects other than acidosis.
Hiroi
K
K
Department of Ophthalmology, Faculty of Medicine, Kyoto University, Japan.
Yamamoto
F
F
Honda
Y
Y
D000818:Animals; D002415:Cats; D003623:Dark Adaptation; D004596:Electroretinography; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000503:physiopathology*; D008839:Microelectrodes; D011188:Potassium; D012160:Retina / Q000502:physiology*
D011188:Potassium