Comparison between the slow cornea-negative PIII component of the ERG and potassium changes in the isolated rabbit retina.
Light-induced extracellular potassium changes were measured in the isolated rabbit retina superfused by a plasma saline mixture and compared with the electroretinogram. When the transmission to second-order neurons was blocked by aspartate and glutamate or by Mg2+, the electroretinogram consisted of the receptor potential and the cornea-negative slow PIII. Since the onset of PIII could then be seen to precede the decrease in extracellular potassium concentration ([K+]0) around photoreceptors, the [K+]0 decrease could not be the cause of the onset of slow PIII. A possible source for the initial phase of slow PIII could be the electrogenic Na+/bicarbonate transporter mechanism of glial cells. Slow PIII depended highly on the extracellular sodium concentration, and it was larger in solutions buffered with bicarbonate than with HEPES, while the [K+]0 decrease around receptors was unchanged.
Hanitzsch
R
R
Carl-Ludwig-Institute of Physiology, University Leipzig, Germany.
D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D002352:Carrier Proteins / Q000502:physiology; D003315:Cornea / Q000502:physiology*; D004596:Electroretinography / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007395:Interneurons / Q000187:drug effects; D008027:Light; D010786:Photoreceptor Cells / Q000502:physiology; D011188:Potassium / Q000502:physiology*; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D027982:Sodium-Bicarbonate Symporters
D002352:Carrier Proteins; D005971:Glutamates; D027982:Sodium-Bicarbonate Symporters; D001224:Aspartic Acid; D018698:Glutamic Acid; D011188:Potassium