title: Statistical and graphical methods for testing the hypothesis that quanta are made up of subunits.
abstract: It has been proposed that at the neuromuscular junction quanta are made up of subunits, because regularly spaced peaks appear in some histograms of miniature end-plate potential (MEPP) amplitudes. Many sets of MEPP sizes fit lognormal probability distribution functions. I compared sets of MEPP amplitudes from the literature to lognormal distributions, using cumulative plots and a robust test for significance. Some data sets fit a single lognormal distribution, but most required two lognormal subpopulations. This bimodal model is a parsimonious alternative to the subunits hypothesis. I also used graphs in which cumulative MEPP sizes were plotted on the ordinate against probability on the abscissa. Model data sets, generated on the subunit assumptions, produced concave plots. End-plate potential sizes at low quantal outputs--in which we know there are subunits--show the same concave shape. Most of the tested data from the subunit literature produced convex curves.
authors.affiliation: Department of Physiology and Biophysics, SUNY, Stony Brook 11794.
authors.forename: W
authors.initials: W
authors.lastname: Van der Kloot
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D008959:Models, Neurological; D009132:Muscles / Q000294:innervation / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D011894:Rana pipiens; D013223:Statistics as Topic; D009435:Synaptic Transmission