Isolated single (Xenopus) muscle fibers were stained with a non-permeant potential-probing dye, merocyanine rhodanine (WW375) or merocyanine oxazolone (NK2367). When the fiber was massively stimulated, an absorption change (wave a), which seemed to reflect the action potential, occurred. Simultaneous recording of optical changes and intracellular action potentials revealed that the time-course of wave a was slower than the action potential: the peak of wave a was attained at 1 ms, and the peak of action potential was reached at 0.5 ms after the stimulation. This difference suggests that wave a represents the potential changes of the whole tubular membrane and the surface membrane, whereas the action potential represents a surface potential change. This idea was substantiated by recording absorption signals preferentially from the surface membrane by recording the absorption changes at the edge of the fiber. Wave a obtained by this method was as quick as the intracellular action potential. The value of radial conduction velocity of action potential along the T system, calculated by comparing the action potential with wave a, was 6.4 cm/s at 24.5 degrees C, in fair agreement with González-Serratos (1971. J. Physiol. [Lond.]. 212:777-799). The shape of wave a suggests the existence of an access delay (a conduction delay at the orifice of the T system) of 130 microseconds.
Article|
December 01 1980
Radial propagation of muscle action potential along the tubular system examined by potential-sensitive dyes.
S Nakajima,
S Nakajima
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
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A Gilai
A Gilai
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Search for other works by this author on:
S Nakajima
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
A Gilai
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1980) 76 (6): 751–762.
Citation
S Nakajima, A Gilai; Radial propagation of muscle action potential along the tubular system examined by potential-sensitive dyes.. J Gen Physiol 1 December 1980; 76 (6): 751–762. doi: https://doi.org/10.1085/jgp.76.6.751
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