Current-evoked transcellular K+ flux in frog retina

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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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
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 > Institute of Infection Immunity and Inflammation
Journal Name:Journal of Neurophysiology
Journal Abbr.:J. neurophysiol.
Publisher:American Physiological Society
ISSN (Online):1522-1598

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