Potassium and the photoreceptor-dependent pigment epithelial hyperpolarization

Light-evoked changes in pigment epithelial cell membrane potentials and retinal extracellular potassium ion concentration, [K+]0, were measured in an in vitro frog retina-pigment epithelium-choroid preparation. Light stimuli hyperpolarized the apical membrane of the pigment epithelium. Through an electrical shunt pathway connecting the apical and basal membranes, the basal membrane also hyperpolarized, but to a lesser degree than the apical membrane. This differential hyperpolariation of the two membranes increased the transepithelial potential (TEP). This increase in TEP was shown to be the major voltage source of the c-wave of the electroretinogram (ERG). Direct measurement of [K+]0 in the distal retina, made with K+-specific microelectrodes, showed a light-evoked decrease in [K+]0 having an identical time course to the apical hyperpolarization. There was a linear relationship between the light-evoked change in TEP and the logarithm of [K+]0. This exact relationship was also found when the apical membrane was perfused directly with solutions of varying [K+]0. The change in TEP associated with the ERC c-wave, therefore, was explained solely by the response of the pigment epithelium to the light-evoked decrease in [K+]0 in the distal retina.

[1]  R. H. Steinberg,et al.  The in vitro frog pigment epithelial cell hyperpolarization in response to light. , 1977, Investigative ophthalmology & visual science.

[2]  D. G. Green,et al.  Correlation of light-induced changes in retinal extracellular potassium concentration with c-wave of the electroretinogram. , 1976, Journal of neurophysiology.

[3]  M. Lurie.  Some observations on the c-wave of the electroretinogram in the intact frog eye. , 1976, Experimental eye research.

[4]  K. Brown,et al.  Instrumentation and technique for beveling fine micropipette electrodes , 1975, Brain Research.

[5]  F. Dudek,et al.  Slow PIII component of the carp electroretinogram , 1975, The Journal of general physiology.

[6]  H. Lux.  Fast recording ion specific microelectrodes: their use in pharmacological studies in the CNS. , 1974, Neuropharmacology.

[7]  R. H. Steinberg,et al.  Aspects of electrolyte transport in frog pigment epithelium. , 1973, Experimental eye research.

[8]  A. Hudspeth,et al.  The intercellular junctional complexes of retinal pigment epithelia. , 1973, Investigative ophthalmology.

[9]  John L. Walker.  Ion specific liquid ion exchanger microelectrodes , 1971 .

[10]  K. Brown,et al.  Intracellular Responses to Light from Cat Pigment Epithelium: Origin of the Electroretinogram c-Wave , 1970, Nature.

[11]  K. Brown,et al.  Melanin and the rapid light-evoked responses from pigment epithelium cells of the frog eye. , 1967, Vision research.

[12]  W. Noell.  Cellular Physiology of the Retina , 1963 .

[13]  T. Wiesel,et al.  Localization of origins of electroretinogram components by intraretinal recording in the intact cat eye , 1961, The Journal of physiology.

[14]  W. Muller-Limmroth,et al.  [Origin of the electroretinogram. I]. , 1958, Zeitschrift fur Biologie.