Premium
The role of calcium ions in tetanic and post‐tetanic increase of miniature end‐plate potential frequency.
Author(s) -
Erulkar S D,
Rahamimoff R
Publication year - 1978
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1978.sp012320
Subject(s) - tetanic stimulation , chemistry , biophysics , electrochemical gradient , calcium , stimulation , neuromuscular junction , ion , membrane potential , electrophysiology , anatomy , long term potentiation , membrane , endocrinology , biochemistry , biology , neuroscience , receptor , organic chemistry
1. The role of Ca ions in transmitter release changes, during and after high frequency stimulation of the motor nerve (10‐‐100 Hz), was examined at the frog neuromuscular junction. 2. The stimulation‐induced changes in miniature end‐plate potential frequency (f) resembled the changes in end‐plate potential amplitude recently described by Magleby and Zengel (1975, 1976). 3. The effects of tetanic stimulation on f under inward electrochemical gradient for Ca ions were compared with those under reversed gradient and four differences were found: (a) The increase in f during the tetanus under reversed Ca gradient conditions is much smaller than with an inward Ca gradient. (b) The increase in f under reversed Ca gradient is preceded by a small decrease in f, whereas with an inward Ca gradient an immediate increase in f is observed. (c) After the termination of the tetanus with a reversed Ca gradient, there is a further increase in f, compared to a decrease with an inward Ca gradient. (d) The augmentation phase of post‐tetanic potentiation was practically abolished. 4. The experimental results are explained by assuming that high frequency nerve stimulation causes an increase in transmitter release by at least two distinct processes: influx of Ca ions through the presynaptic membrane and release of Ca ions from intracellular stores. It is suggested that Na ions couple nerve activity to intracellular release of Ca.