Spatial Buffering of Light-Evoked Potassium Increases by Retinal Müller (Glial) Cells

• Published in: Science (American Association for the Advancement of Science) Vol. 244; no. 4904; pp. 578 - 580
• Main Authors: Karwoski, Chester J., Lu, Hong-Kai, Newman, Eric A.
• Format: Journal Article
• Language: English
• Published: Washington, DC The American Association for the Advancement of Science 05.05.1989; American Association for the Advancement of Science
• Subjects: Ambystoma; Amphibians; Animals; Barium; Barium - pharmacology; Biochemistry; Bioelectrochemistry; Biological and medical sciences; Electric Conductivity; Electrodes; Eye and associated structures. Visual pathways and centers. Vision; Eyes & eyesight; Fundamental and applied biological sciences. Psychology; Ganglia; Glia; Light; Measurement; Medical research; Modeling; Necturus maculosus; Neuroglia; Neuroglia - drug effects; Neuroglia - metabolism; Neuroglia - radiation effects; Neuroscience; Potassium; Potassium (Chemical element); Potassium - metabolism; Potassium Channels - physiology; Rana pipiens; Retina; Retina - cytology; Simulations; Vertebrates: nervous system and sense organs; Vitreous body; Vitreous Body - metabolism; Frog; Amphibia; Electrophysiology; Luminous stimulus; Retina; Salientia; Muller cell; Ionic current; Inorganic element; Eye; Vertebrata; Light; Potassium
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.2785716

Activity-dependent variations in extracellular potassium concentration in the central nervous system may be regulated, in part, by potassium spatial buffering currents in glial cells. The role of spatial buffering in the retina was assessed by measuring light-evoked potassium changes in amphibian eyecups. The amplitude of potassium increases in the vitreous humor was reduced to $\sim $10 percent by 50 micromolar barium, while potassium increases in the inner plexiform layer were largely unchanged. The decrease in the vitreal potassium response was accurately simulated with a numerical model of potassium current flow through Muller cells, the principal glial cells of the retina. Barium also substantially increased the input resistance of Muller cells and blocked the Muller cell-generated M-wave, indicating that barium blocks the potassium channels of Muller cells. Thus, after a light-evoked potassium increase within the retina, there is a substantial transfer of potassium from the retina to the vitreous humor by potassium current flow through Muller cells.