title: Electrical membrane properties of the muscle lamellae in Branchiostoma myotomes.
abstract: The membrane characteristics of amphioxus myotome cells were investigated using the chopped-current clamp method. The extremely thin myotome lamellae had a membrane resistance of 2.2 to 7.7 k omega cm2 and a capacity of 0.4 to 1.3 microF/micron2. The steady state current-voltage relation showed outward rectification. In Cl- - and Na+ -free solutions containing 400 mM TEA the input resistance and the time constant increased threefold and Ca2+ -dependent action potentials occurred, indicating the presence of a Ca2+ component in membrane current. It is discussed whether Ca2+ ions entering the cell during the normal action potential may significantly increase the intracellular free Ca2+ concentration.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002816:Chordata, Nonvertebrate / Q000502:physiology*; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology* / Q000648:ultrastructure; D009210:Myofibrils / Q000648:ultrastructure; D011343:Procaine / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D013757:Tetraethylammonium Compounds; D011343:Procaine; D019789:Tetraethylammonium; D002118:Calcium