Role of Calcium in Desensitization at the Motor End-Plate of Skeletal Muscle

  • Rodney L. Parsons


When acetylcholine or other depolarizing compounds are applied to the motor end-plate region of skeletal muscle fibers, the post-junctional membrane undergoes a rapid increase in ionic conductance as the cholinergic receptors are activated. This agonist-induced increase in ionic conductance remains for a short period and then reverses even though the agonist application is continued. Thesleff (1955) initially studied this phenomenon using intracellular recordings of the drug-induced depolarization-repolarization sequence produced in individual muscle fibers during sustained application of depolarizing drugs. As repolarization occurred, nerve evoked end-plate potentials were reduced progressively and subsequent application of agonist produced no additional depolarization (Thesleff, 1955). Under these conditions, the end-plate membrane receptors gradually became refractory to agonist action and were said to be “desensitized” (Thesleff, 1955).


Frog Skeletal Muscle Agonist Concentration Frog Neuromuscular Junction Input Conductance Agonist Application 
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Copyright information

© Plenum Press, New York 1978

Authors and Affiliations

  • Rodney L. Parsons
    • 1
  1. 1.Department of Physiology and BiophysicsUniversity of VermontBurlingtonUSA

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