Interaction between sodium and calcium ions in the process of transmitter release at the neuromuscular junction
- 1 September 1968
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 198 (1), 203-218
- https://doi.org/10.1113/jphysiol.1968.sp008602
Abstract
1. The interaction between Na and Ca ions on quantal transmitter release at the frog neuromuscular junction has been studied, using intracellular recording and averaging of responses.2. At low calcium concentrations, partial withdrawal of Na ions increases end-plate potential (e.p.p.) amplitudes and quantal content (m) and decreases the amplitude of the miniature e.p.p.s (m.e.p.p.s). Under these conditions the relation between [Ca] and m is highly non-linear. When plotted on double logarithmic co-ordinates withdrawal of [Na] causes a nearly parallel shift of this relation.3. Mutual interaction occurs between Ca, Na and Mg in transmitter release. With a constant low [Ca] in the medium, withdrawal of [Na] produces a smaller increase in m when [Mg] is high, than when [Mg] is low.4. In the presence of normal [Ca] (1.8 mM), [Na] withdrawal decreases the amplitude of the e.p.p. and produces a small decrease in m.5. The results can be explained by assuming that [Na] reduction has two mutually opposing effects on transmitter release: it makes more sites available for the action of Ca, and it lowers the amplitude of the action potential in the nerve terminals. The former effect dominates at low, the latter at high, calcium concentrations.Keywords
This publication has 19 references indexed in Scilit:
- Effect of Bromide Ions on Junctional TransmissionNature, 1968
- Co‐operative action of calcium ions in transmitter release at the neuromuscular junctionThe Journal of Physiology, 1967
- Inhibitory Action of Sodium Ions on Transmitter Release at the Motor End-plateNature, 1967
- The release of acetylcholine from nerve endings by graded electric pulsesProceedings of the Royal Society of London. B. Biological Sciences, 1967
- Calcium and the Contraction of the Heart: Antagonism between Calcium and Sodium IonsNature, 1957
- The effects of osmotic pressure changes on the spontaneous activity at motor nerve endingsThe Journal of Physiology, 1956
- Biophysical Aspects of Neuro-muscular TransmissionProgress in Biophysics and Biophysical Chemistry, 1956
- A further study of the statistical composition of the end‐plate potentialThe Journal of Physiology, 1955
- Quantal components of the end‐plate potentialThe Journal of Physiology, 1954
- The effect of sodium ions on neuromuscular transmissionThe Journal of Physiology, 1952