title: Localizing quantal currents along frog neuromuscular junctions.
abstract: 1. We spatially localized the origins of quantal currents by recording simultaneously with two intracellular electrodes and employing the prediction of the one-dimensional cable equations that the time integrals of the resulting voltage changes fall off exponentially with distance. 2. Miniature endplate potentials (MEPPs) were more frequent near the 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 potentials (EPPs) were released over the same length of endplate and with the same relative probabilities at different regions. 4. Nicotinic agonists decreased evoked quantal output, but did not change the length over which uniquantal EPPs were generated. We conclude they do not block nerve conduction in the terminals. 5. Data sets were obtained with an extracellular electrode and two intracellular electrodes. The extracellular electrode was invariably near the centre of the region in which congruous MEPPs appeared to be generated. However, the range in the calculated positions of the synchronous MEPPs was as long as 0.8 mm. Therefore, it may be possible that extracellular electrodes have a longer recording range than commonly assumed.
authors.affiliation: Department of Physiology and Biophysics, State University of New York, Stony Brook 11794-8661, USA. wvanderkloot@ccmail.sunysb.edu
authors.forename: W
authors.initials: W
authors.lastname: Van der Kloot
authors.forename: L A
authors.initials: LA
authors.lastname: Naves
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology; D005942:Gluconates / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000502:physiology*; D009469:Neuromuscular Junction / Q000378:metabolism*; D018722:Nicotinic Agonists / Q000494:pharmacology; D011894:Rana pipiens
chemical_list: D005942:Gluconates; D018722:Nicotinic Agonists; D002217:Carbachol; C030691:gluconic acid