Membrane potential changes that typically evoke transmitter release were studied by recording intracellularly from the excitor axon near presynaptic terminals of the crayfish opener neuromuscular junction. Depolarization of the presynaptic terminal with intracellular current pulses activated a conductance that caused a decrease in depolarization during the constant current pulse. This conductance was identified as a calcium-activated potassium conductance, gK(Ca), by its disappearance in a zero-calcium/EGTA medium and its block by cadmium, barium, tetraethylammonium ions, and charybdotoxin. In addition to gK(Ca), a delayed rectifier potassium conductance (gK) is present in or near the presynaptic terminal. Both these potassium conductances are involved in the repolarization of the membrane during a presynaptic action potential.
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1 December 1991
Article|
December 01 1991
Calcium-activated potassium conductance in presynaptic terminals at the crayfish neuromuscular junction.
S Sivaramakrishnan,
S Sivaramakrishnan
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
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G D Bittner,
G D Bittner
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
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M S Brodwick
M S Brodwick
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
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S Sivaramakrishnan
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
G D Bittner
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
M S Brodwick
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
Online ISSN: 1540-7748
Print ISSN: 0022-1295
J Gen Physiol (1991) 98 (6): 1161–1179.
Citation
S Sivaramakrishnan, G D Bittner, M S Brodwick; Calcium-activated potassium conductance in presynaptic terminals at the crayfish neuromuscular junction.. J Gen Physiol 1 December 1991; 98 (6): 1161–1179. doi: https://doi.org/10.1085/jgp.98.6.1161
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