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Sodium Current Amplitude Increases Dramatically in Human Retinal Glial Cells during Diseases of the Eye
Author(s) -
Francke M.,
Pannicke T.,
Biedermann B.,
Faude F.,
Reichelt W.
Publication year - 1996
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1996.tb01561.x
Subject(s) - retinal , neuroscience , retina , current (fluid) , psychology , physics , ophthalmology , medicine , thermodynamics
Müller cells, the main macroglial cells of the retina, express several types of voltage and ligand‐activated ion channels, including Na ‐ channels. Using the whole‐cell voltage‐clamp technique, we studied the expression of Na ‐ currents in acutely isolated, non‐cultivated human Muller cells from retinas of healthy organ donors and patients suffering from different eye diseases. In both types of retinas transient Na+ currents could be recorded from Muller cells. The tetrodotoxin‐resistant Na + currents, which were not completely blocked even at a concentration of 10 $muM tetrodotoxin, had a mean current density of 3.0± 3.0 pA/pF (mean ± SD, n = 10) in Muller cells from donor retinas and of 12.2± 2 9.6 pA/pF ( n = 74) in Muller cells from patient retinas. Only 33.3% of healthy but 88.4% of pathological Muller cells depicted such currents. The G Na+ /G K+ ratio was very high in several Muller cells from patient retinas, such that action potential‐like activity could be generated after prehyperpolarizing current injection in some of these cells. Apparently, the Na’channels, due to their negative steady‐state inactivation curve (V h = ‐84.5 mV), do not influence the lowered membrane potential of the pathological cells, since they are inactivated at these voltages. Currently, we do not have an explanation for the increase in amplitude and frequency of Na+ currents in human Muller cells under pathological conditions. However, the up‐regulation of Na channels may mirror a basic glial response to pathological conditions, since it has also been found previously in human hippocampal astrocytes from epileptic foci and in rat cortex stab wounds lined by an astrocytic scar.