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Effects of repetitive stimulation, veratridine and ouabain on cytoplasmic pH in frog nerve fibres: role of internal Na +
Author(s) -
Valkina O.N.,
Vergun O.V.,
Turovetsky V.B.,
Khodorov B.I.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)81686-t
Subject(s) - veratridine , ouabain , stimulation , chemistry , biophysics , sodium , fluorescein , fluorescence , endocrinology , sodium channel , biology , physics , organic chemistry , quantum mechanics
Changes of cytoplasmic pH (pH i ) in frog nerve fibres during repetitive stimulation have been measured using the fluorescent pH indicator dye fluorescein diacetate (FDA). Under control conditions repetitive (10–50 Hz) stimulation caused only a very small decrease in pH i (by 0.015–0.06 pH units). Modification of Na + channels by veratridine (VER, 10, μM) greatly increased this stimulus‐evoked (SE) internal acidification. Blockade of the Na + ‐K + pump by ouabain (0.5 mM) enhanced the effects VER and prevented pH i recovery after the termination of repetitive stimulation. A similar inhibition of post‐stimulatory recovery of pH i was observed after replacement of external Na + with Li + , which is not accepted by the Na + ‐K + pump instead of Na + . These data suggest that SE intracellular acidification in nerves results from or is closely associated with an increase in [Na + ] i . Treatments that promote Na + influx and accumulation of Na + inside the fibre enhance reduction of pH i . Li + can be substituted for Na + in this process.