Abstract
The rate at which the postjunctional membrane of muscle fibers becomes desensitized to the action of carbamylcholine is increased after the muscle has been soaked in solutions containing increased concentrations of calcium. Some further aspects of this effect of calcium were investigated by measuring changes in the input resistance of single fibers of the frog sartorius during local perfusion of the neuromuscular junction with 2.73 x 10-3 M carbamylcholine in isolated muscles immersed in 165 mM potassium acetate. It was found that (a) sudden changes in the local concentration of calcium brought about by perfusing fibers with carbamylcholine solutions containing 20 mM calcium, 40 mM oxalate, or 40 mM EDTA were followed within 20 sec by marked changes in the rate of desensitization; (b) prior to 13 sec after the introduction of carbamylcholine, however, no effect on the input resistance could be detected even though the muscle had been presoaked in 10 mM calcium; (c) the ability of high concentrations of calcium to bring about rapid desensitization disappears when a lower concentration of carbamylcholine (0.137 x 10-3 M) is applied to the muscle fiber. These findings suggest that calcium present in the extracellular fluid can act directly on the postjunctional membrane to promote the desensitization process and that an increased permeability of the membrane to calcium brought about by the presence of carbamylcholine is a factor which contributes to this action.
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Selected References
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- COSMOS E., HARRIS E. J. In vitro studies of the gain and exchange of calcium in frog skeletal muscle. J Gen Physiol. 1961 Jul;44:1121–1130. doi: 10.1085/jgp.44.6.1121. [DOI] [PMC free article] [PubMed] [Google Scholar]
- CURTIS D. R., ECCLES R. M. The excitation of Renshaw cells by pharmacological agents applied electrophoretically. J Physiol. 1958 May 28;141(3):435–445. doi: 10.1113/jphysiol.1958.sp005987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DEL CASTILLO L., KATZ B. A study of curare action with an electrical micromethod. Proc R Soc Lond B Biol Sci. 1957 May 7;146(924):339–356. doi: 10.1098/rspb.1957.0015. [DOI] [PubMed] [Google Scholar]
- FOREMAN H., VIER M., MAGEE M. The metabolism of C14-labeled ethylenediaminetetraacetic acid in the rat. J Biol Chem. 1953 Aug;203(2):1045–1053. [PubMed] [Google Scholar]
- FURCHGOTT R. F., SLEATOR W., Jr, DE GUBAREFF T. Effects of acetylcholine and epinephrine on the contractile strength and action potential of electrically driven guinea pig atria. J Pharmacol Exp Ther. 1960 Aug;129:405–416. [PubMed] [Google Scholar]
- Manthey A. A. The effect of calcium on the desensitization of membrane receptors at the neuromuscular junction. J Gen Physiol. 1966 May;49(5):963–976. doi: 10.1085/jgp.49.5.963. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nastuk W. L., Manthey A. A., Gissen A. J. Activation and inactivation of postjunctional membrane receptors. Ann N Y Acad Sci. 1966 Jul 14;137(2):999–1014. doi: 10.1111/j.1749-6632.1966.tb50212.x. [DOI] [PubMed] [Google Scholar]
- TAKEUCHI N. Effects of calcium on the conductance change of the end-plate membrane during the action of transmitter. J Physiol. 1963 Jun;167:141–155. doi: 10.1113/jphysiol.1963.sp007137. [DOI] [PMC free article] [PubMed] [Google Scholar]
- TAYLOR D. B., NEDERGAARD O. A. RELATION BETWEEN STRUCTURE AND ACTION OF QUATERNARY AMMONIUM NEUROMUSCULAR BLOCKING AGENTS. Physiol Rev. 1965 Jul;45:523–554. doi: 10.1152/physrev.1965.45.3.523. [DOI] [PubMed] [Google Scholar]
- THESLEFT S. The mode of neuromuscular block caused by acetylcholine, nicotine, decamethonium and succinylcholine. Acta Physiol Scand. 1955 Oct 27;34(2-3):218–231. doi: 10.1111/j.1748-1716.1955.tb01242.x. [DOI] [PubMed] [Google Scholar]