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Pharmacological separation of charge movement components in frog skeletal muscle
Author(s) -
Huang C. L.-H.
Publication year - 1982
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.1982.sp014118
Subject(s) - tetracaine , depolarization , capacitance , chemistry , charge (physics) , analytical chemistry (journal) , biophysics , materials science , lidocaine , physics , electrode , chromatography , neuroscience , biology , quantum mechanics
1. Charge movements to small 10 mV steps superimposed upon a wide range of closely spaced depolarizing voltage‐clamp pulses were studied in frog skeletal muscles under different pharmacological conditions in hypertonic solutions. 2. In control fibres, capacitance was strongly voltage‐dependent, especially between potentials of ‐60 and ‐20 mV, confirming earlier work. There was a sharp increase in capacitance at around ‐50 mV. The dependence of non‐linear charge on potential was asymmetrical and saturated at around 25 nC/μF. 3. The presence of tetracaine abolished the ‘hump’ in the non‐linear transients, which became simple monotonic decays. The dependence of capacitance upon potential was reduced. The maximum available amount of non‐linear charge fell to 10 nC/μF. 4. The presence of lidocaine abolished both the ‘hump’ as well as the monotonic part of the non‐linear transients. This resulted in capacitance falling with depolarization from ‐85 mV. 5. Comparing the steady‐state properties of the non‐linear charge under the different pharmacological conditions made it possible to deduce empirically the following components: (i) A lidocaine‐resistant component ( q α ), which was responsible for the fall in observed capacitance with depolarization from the control voltage. (ii) A component resistant to tetracaine yet abolished by lidocaine ( q β ). This possesses quasi‐exponential kinetics, and a maximum charge of about 20 nC/μF. (iii) A component abolished by both lidocaine and tetracaine ( q γ ), which possesses a maximum charge of 15 nC/μF. This has complex kinetics, and its steep dependence upon voltage resembles the potential‐dependence of the development of tension in skeletal muscle.