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. 1966 Mar;49(4):807-18.
doi: 10.1085/jgp.49.4.807.

Effects of the intracellular Ca ion concentration upon the excitability of the muscle fiber membrane of a barnacle

S Hagiwara, S Nakajima

Effects of the intracellular Ca ion concentration upon the excitability of the muscle fiber membrane of a barnacle

S Hagiwara et al. J Gen Physiol. 1966 Mar.

Abstract

The membrane excitability and contraction were examined in single barnacle muscle fibers with different internal Ca(++) concentrations by using buffer solutions made up with EGTA and Ca-gluconate in various proportions. During the passage of dc currents the membrane shows all-or-none spike potentials for internal Ca(++) concentrations below about 8 x 10(-8)M, oscillatory potential changes in the range between 8 x 10(-8) to 5 x 10(-7)M, but neither oscillatory nor spike potentials were seen for concentrations above 5 x 10(-7)M. All-or-none spike potentials were suppressed when the internal Mg(++) concentration exceeded 5 mM. The suppression threshold of the internal Ca(++) concentration for the Sr spike is much higher than that for the Ca spike. The threshold concentration of internal Ca(++) for contraction was about 8 x 10(-7)M.

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