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Twitch potentiation by potassium contractures in single muscle fibres of the frog
Author(s) -
Chiarandini D. J.,
Stefani E.
Publication year - 1974
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1974.sp010595
Subject(s) - long term potentiation , muscle contracture , contracture , isometric exercise , chemistry , refractory period , potassium , anatomy , biophysics , medicine , biology , biochemistry , surgery , receptor , organic chemistry
1. The modifications of isometric twitches after K contractures have been studied in single muscle fibres from frog muscles. 2. The twitch was greatly enhanced and somewhat prolonged after a conditioning K contracture. This potentiating effect was more evident in fibres having low values of the ratio control twitch tension/tetanus tension ( P/P 0 ). 3. In most of the fibres, the time course of the decay of the potentiation phenomenon could be represented by the sum of three negative exponentials with average half‐times of 9·1, 40 and 485 sec. 4. Between 3 and 10 min after the onset of the twitch potentiation the resting potential and action potential were unchanged. 5. Mn blocked the K contractures and prevented the onset of the twitch potentiation. 6. 40–140 sec after inducing a K contracture with 30 or 40 m M ‐K, a second exposure to the same [K] evoked a tension equivalent only to 57% of the first one. This partial refractoriness of the fibres is not seen when both contractures were elicited with 190 m M ‐K, and contrasts with the full recovery and potentiation of the twitch after a K contracture.