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High potassium induces taurine release by osmosensitive and osmoresistant mechanisms in the rat hippocampus in vivo
Author(s) -
RodríguezNavarro José A.,
GonzaloGobernado Rafael,
Herranz Antonio S.,
GonźlezVigueras José M.,
Solís José M.
Publication year - 2009
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.21818
Subject(s) - taurine , microdialysis , potassium , chemistry , extracellular , nmda receptor , depolarization , glutamate receptor , biophysics , medicine , endocrinology , biochemistry , amino acid , receptor , biology , organic chemistry
The high potassium‐evoked taurine efflux in the nervous tissue has been entirely considered to be the result of the cell swelling produced by KCl influx via passive Donnan forces. However, the extracellular taurine increase evoked in the hippocampus by applying 6–100 mM KCl through microdialysis probes, which saturates at a concentration of 25 mM KCl, is not congruent with the mentioned osmosensitive release of taurine stimulated by high potassium. Therefore, we studied whether the taurine release elicited by different high KCl concentrations (25, 50, 75, or 100 mM) was blocked under hypertonic conditions (+100 mM sucrose). Taurine release stimulated by 25 mM KCl was totally osmosensitive, but that released by higher KCl concentrations became progressively osmoresistant, achieving more than the 60% of the extracellular taurine enhancement during 100 mM KCl perfusion. The osmoresistant taurine release evoked by 100 mM KCl perfusion was partially reduced by a solution without Ca 2+ and with high Mg 2+ , or by D,L ‐2‐amino‐5‐phosphopentanoic acid, an N‐methyl‐ D ‐aspartic acid (NMDA) receptor antagonist. Moreover, the release of taurine induced by a hypoosmotic solution was reduced by the presence ofeither high K + (75 mM) or NMDA (100 μM). These results indicate that although moderately high [K + ] evoke the osmosensitive release of taurine, higher [K + ] inhibit it and trigger the release of taurine by an osmoresistant mechanism. This last component is partially mediated by NMDA receptors activated by the glutamate released during potassium‐induced depolarization. © 2008 Wiley‐Liss, Inc.