Karwoski, C. J., Coles, J. A., Lu, H.-K. and Huang, B. (1989) Current-evoked transcellular K+ flux in frog retina. Journal of Neurophysiology, 61(5), pp. 939-952.
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Publisher's URL: http://jn.physiology.org/content/61/5/939
Abstract
1. Changes in extracellular K+ concentration (delta[K+]o) evoked by electrical current were measured with K+-selective microelectrodes (K-ISMs) in the retina of the frog eyecup. 2. In the superfusate at 20 microns above the inner limiting membrane (ILM), current-evoked delta[K+] was a function of current polarity and strength; its amplitude decreased as the K-ISM was moved higher above the ILM. Responses were similar whether measured with K-ISMs containing the Corning exchanger or a valinomycin-based liquid membrane. No current-evoked delta[Ca2+] could be detected with Ca-selective microelectrodes (Ca-ISMs). 3. Within the retina, a complex spatiotemporal profile of current-evoked delta[K+]o was observed. Strophanthidin abolished responses in the proximal retina, but had little effect on the response in the superfusate. A blocker of K+ channels (Ba2+) depressed responses in the superfusate, but not in the proximal retina. 4. Quantitative analysis of these responses indicates a transport number for K+ of 0.18 at onset of current, and that decreases over a few seconds. In contrast, a transport number of approximately 0.01 is predicted from the expected ionic concentrations within extracellular space. 5. These findings are compatible with the delta[K+] above the ILM being due to transcellular movement of K+ through Muller cells. The results suggest that K+ spatial buffering may be particularly potent in the retina. Furthermore, determinations of tissue characteristics by passage of electrical current must take into account that at least 17% of the current does not travel through extracellular space.
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Coles, Dr Jonathan |
Authors: | Karwoski, C. J., Coles, J. A., Lu, H.-K., and Huang, B. |
College/School: | College of Medical Veterinary and Life Sciences > School of Infection & Immunity |
Journal Name: | Journal of Neurophysiology |
Journal Abbr.: | J. neurophysiol. |
Publisher: | American Physiological Society |
ISSN: | 0022-3077 |
ISSN (Online): | 1522-1598 |
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