LOCALIZING QUANTAL CURRENTS ALONG FROG NEUROMUSCULAR-JUNCTIONS

Citation
W. Vanderkloot et La. Naves, LOCALIZING QUANTAL CURRENTS ALONG FROG NEUROMUSCULAR-JUNCTIONS, Journal of physiology, 497(1), 1996, pp. 189-198
Citations number
31
Categorie Soggetti
Physiology
Journal title
ISSN journal
00223751
Volume
497
Issue
1
Year of publication
1996
Pages
189 - 198
Database
ISI
SICI code
0022-3751(1996)497:1<189:LQCAFN>2.0.ZU;2-H
Abstract
1. We spatially localized the origins of quantal currents by recording simultaneously with two intracellular electrodes and employing the pr ediction of the one-dimensional cable equations that the time integral s of the resulting voltage changes fall off exponentially with distanc e. 2. Miniature endplate potentials (MEPPs) were more frequent near th e centre of the endplate. In contrast to some work using other methods , we did not find MEPPs originating at the margins of the endplate to be strikingly smaller. 3. Spontaneous MEPPs and uniquantal endplate po tentials (EPPs) were released over the same length of endplate and wit h the same relative probabilities at different regions. 4. Nicotinic a gonists decreased evoked quantal output, but did not change the length over which uniquantal EPPs were generated. We conclude they do not bl ock nerve conduction in the terminals. 5. Data sets were obtained with an extracellular electrode and two intracellular electrodes. The extr acellular electrode was invariably near the centre of the region in wh ich congruous MEPPs appeared to be generated. However, the range in th e calculated positions of the synchronous MEPPs was as long as 0.8 mm. Therefore, it may be possible that extracellular electrodes have a lo nger recording range than commonly assumed.