Abstract
Conventional electrophysiological techniques were used to study the effects of Ba on the release of acetylcholine (ACh) from frog motor nerve terminals. Equimolar substitution of Ba for Ca eliminated end-plate potentials (e.p.ps) without a corresponding decline in the amplitude of the nerve terminal action potential. Miniature end-plate potentials (m.e.p.ps) were readily detectable in Ba solutions despite a depolarized muscle membrane. Studies on the e.p.p. in curarized preparations bathed with different concentrations of Ca and Ba suggest that Ba may compete with Ca in the process by which depolarization of the nerve terminal leads to the release of ACh. Repetitive nerve stimulation at 1 Hz in Ba solutions caused 5-20 fold increases in m.e.p.p. frequencies (7 experiments). Stimulation of Ba-bathed preparations at 10 Hz elevated m.e.p.p. frequencies to very high levels that could not be measured accurately (''100/s). It is suggested that the asynchronous discharge of m.e.p.ps produced by repetitive nerve stimulation is the electrophysiological correlate of the evoked ACh outflow in Ba solutions detected previously by bioassay of ther perfusion fluid.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Blioch Z. L., Glagoleva I. M., Liberman E. A., Nenashev V. A. A study of the mechanism of quantal transmitter release at a chemical synapse. J Physiol. 1968 Nov;199(1):11–35. doi: 10.1113/jphysiol.1968.sp008637. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Braun M., Schmidt R. F., Zimmermann M. Facilitation at the frog neuromuscular junction during and after repetitive stimulation. Pflugers Arch Gesamte Physiol Menschen Tiere. 1966;287(1):41–55. doi: 10.1007/BF00362453. [DOI] [PubMed] [Google Scholar]
- DOUGLAS W. W., LYWOOD D. W., STRAUB R. W. The stimulant effect of barium on the release of acetylcholine from the superior cervical ganglion. J Physiol. 1961 May;156:515–522. doi: 10.1113/jphysiol.1961.sp006690. [DOI] [PMC free article] [PubMed] [Google Scholar]
- FATT P., KATZ B. An analysis of the end-plate potential recorded with an intracellular electrode. J Physiol. 1951 Nov 28;115(3):320–370. doi: 10.1113/jphysiol.1951.sp004675. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HUBBARD J. I., SCHMIDT R. F. An electrophysiological investigation of mammalian motor nerve terminals. J Physiol. 1963 Apr;166:145–167. doi: 10.1113/jphysiol.1963.sp007096. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hubbard J. I. Microphysiology of vertebrate neuromuscular transmission. Physiol Rev. 1973 Jul;53(3):674–723. doi: 10.1152/physrev.1973.53.3.674. [DOI] [PubMed] [Google Scholar]
- Hurlbut W. P., Longenecker H. B., Jr, Mauro A. Effects of calcium and magnesium on the frequency of miniature end-plate potentials during prolonged tetanization. J Physiol. 1971 Dec;219(1):17–38. doi: 10.1113/jphysiol.1971.sp009647. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Katz B., Miledi R. The statistical nature of the acetycholine potential and its molecular components. J Physiol. 1972 Aug;224(3):665–699. doi: 10.1113/jphysiol.1972.sp009918. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Laskowski M. B., Thies R. Interactions between calcium and barium on the spontaneous release of transmitter from mammalian motor nerve terminals. Int J Neurosci. 1972 Jul;4(1):11–16. doi: 10.3109/00207457209147159. [DOI] [PubMed] [Google Scholar]
- Miledi R., Thies R. Tetanic and post-tetanic rise in frequency of miniature end-plate potentials in low-calcium solutions. J Physiol. 1971 Jan;212(1):245–257. doi: 10.1113/jphysiol.1971.sp009320. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sacchi O., Perri V. Quantal mechanism of transmitter release during progressive depletion of the presynaptic stores at a ganglionic synapse. The action of hemicholinium-3 and thiamine deprivation. J Gen Physiol. 1973 Mar;61(3):342–360. doi: 10.1085/jgp.61.3.342. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Silinsky E. M. The effects of bretylium and guanethidine on catecholaminergic transmission in an invertebrate. Br J Pharmacol. 1974 Jul;51(3):367–371. doi: 10.1111/j.1476-5381.1974.tb10671.x. [DOI] [PMC free article] [PubMed] [Google Scholar]