Vesicle size and transmitter release at the frog neuromuscular junction when quantal acetylcholine content is increased or decreased

28Citations
Citations of this article
27Readers
Mendeley users who have this article in their library.
Get full text

Abstract

We investigated whether the synaptic vesicles at the neuromuscular junction change size when their acetylcholine (ACh) content is altered. The size of the miniature endplate potential (MEPP) increased 3- or 4-fold in preparations pre-treated in a hypertonic solution in which the anion was gluconate. We measured the dimensions of synaptic vesicles in such preparations and in controls. The size of the vesicles and size distribution were indistinguishable. Quanta contained about half of the usual amount of ACh in preparations stimulated in the presence of hemicholinium-3, an inhibitor of choline uptake, or in NH4+, which diminishes the proton gradient for ACh uptake into the vesicles. Neither treatment changed the size of the synaptic vesicles. ACh content and vesicle size were both decreased in preparations stimulated in (-)-vesamicol, an inhibitor of ACh uptake in vesicles. Since the other inhibitors decreased ACh content by a similar amount without altering vesicle size, (-)-vesamicol may decrease vesicle size by acting on another target. We also found that a hypertonic solution in which the anion was aspartate increased quantal size similar to gluconate. Both anions have high hydration energy and a large volume. When these treatments increased quantal size the mean 20-80 % rise time of MEPPs recorded with an extracellular electrode was 170 μs. In the controls it was 97 μs. Perhaps some of the added ACh is bound within the vesicles, which slows the rise. Our major conclusion is that ACh content can change notably without any change in the size of the synaptic vesicles.

Cite

CITATION STYLE

APA

Van Der Kloot, W., Molgó, J., Cameron, R., & Colasante, C. (2002). Vesicle size and transmitter release at the frog neuromuscular junction when quantal acetylcholine content is increased or decreased. Journal of Physiology, 541(2), 385–393. https://doi.org/10.1113/jphysiol.2001.014407

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free