TY - JOUR
T1 - Calcium dependent action potentials in skeletal muscle fibres of a beetle larva, Xylotrupes dichotomus
AU - Fukuda, Jun
AU - Furuyama, Shunsuke
AU - Kawa, Kazuyoshi
PY - 1977
Y1 - 1977
N2 - The ionic requirement for generating action potentials in ventral longitudinal muscle fibers dissected from beetle larvae was examined by conventional electrophysiological techniques. Muscle fibers that generated only graded responses in physiological saline were able to generate an all-or-none action potential when the potassium permeability of the membrane was inhibited by tetraethylammonium+ added to the saline. The peak of the action potential thus elicited was intimately related to the external Ca++ concentration. The action potential was blocked by Co++ which is known as a competitive inhibitor of Ca-spikes. Neither tetrodotoxin (3 μM) nor a Na-free condition effectively blocked the generation of the action potential. Mg++ induced a shift in the peak of the action potential; this was, however, due to the stabilizing action of Mg++ but not due to the penetration of Mg++ through the muscle membrane. No action potential was elicited in the muscle fiber when immersed in a Ca-free, EGTA saline even when a high concentration of either Mg++, Na+, or tetraethylammonium+ was present. The action potential of the larval muscle fiber was thus concluded to be a Ca-spike, through the channel of which Na+ or Mg++ did not penetrate.
AB - The ionic requirement for generating action potentials in ventral longitudinal muscle fibers dissected from beetle larvae was examined by conventional electrophysiological techniques. Muscle fibers that generated only graded responses in physiological saline were able to generate an all-or-none action potential when the potassium permeability of the membrane was inhibited by tetraethylammonium+ added to the saline. The peak of the action potential thus elicited was intimately related to the external Ca++ concentration. The action potential was blocked by Co++ which is known as a competitive inhibitor of Ca-spikes. Neither tetrodotoxin (3 μM) nor a Na-free condition effectively blocked the generation of the action potential. Mg++ induced a shift in the peak of the action potential; this was, however, due to the stabilizing action of Mg++ but not due to the penetration of Mg++ through the muscle membrane. No action potential was elicited in the muscle fiber when immersed in a Ca-free, EGTA saline even when a high concentration of either Mg++, Na+, or tetraethylammonium+ was present. The action potential of the larval muscle fiber was thus concluded to be a Ca-spike, through the channel of which Na+ or Mg++ did not penetrate.
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U2 - 10.1016/0022-1910(77)90275-X
DO - 10.1016/0022-1910(77)90275-X
M3 - Article
C2 - 886195
AN - SCOPUS:0017324138
VL - 23
SP - 367
EP - 374
JO - Journal of Insect Physiology
JF - Journal of Insect Physiology
SN - 0022-1910
IS - 3
ER -