Intracellular potassium activities of horizontal cells and extracellular potassium activity in isolated retinae of a cyprinid fish.
Extracellular and intracellular K+ activities of luminosity and biphasic-chromaticity type horizontal cells were measured in non-superfused roach retinae using double-barrelled K+-sensitive micro-electrodes. The extracellular K+ activity in dark-adapted retinae was 3.4 mM on average. The intracellular K+ activities of the two types of horizontal cell in the dark were very similar (57 and 54 mM, respectively), and corresponding values of the K+ equilibrium potential were about 35 mV more negative than respective resting potentials. During light-evoked hyperpolarizations, the intracellular K+ activity decreased, and at saturation, resting potentials matched corresponding K+ equilibrium potentials. The results are discussed in relation to sub-synaptic and non-synaptic membrane ionic mechanisms and further support the view that the non-synaptic membrane is selectively permeable to K+.
Djamgoz
M B
MB
Department of Pure and Applied Biology, Imperial College, London, England.
Laming
P J
PJ
D000818:Animals; D003530:Cyprinidae / Q000378:metabolism*; D003623:Dark Adaptation; D066298:In Vitro Techniques; D008027:Light; D008564:Membrane Potentials; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*
D011188:Potassium