Electrophysiological studies of normal and degenerating mouse neuromuscular junctions.
A quantitative study of the functional changes occurring at end-plates of phrenicotomised mouse hemidiaphragms was made. Analysis of the frequency of spontaneous transmitter release revealed large scale deviations from a Poisson based process commencing 6-7 h post-phrenicotomy. Short term bursts of miniature end-plate potentials (minEPPs) lasting 0.5-1.0 sec frequently occurred and also long term bursts of minEPPs which lasted from several minutes to 0.5 h or more. Following the long term bursts there was regularly a lasting silence at the end-plates. MinEPP amplitudes were analysed. Probability analyses suggest that the minEPPs are often normally distributed amongst two or more populations. This relationship was maintained during degeneration of the end-plate. No significant differences between the distribution of mean minEPP amplitudes of degenerating end-plates and normal end-plates were found. This suggests that no change in the quantal unit of transmitter release occurs during degeneration of the end-plate.
D000200:Action Potentials; D000818:Animals; D003964:Diaphragm / Q000294:innervation; D066298:In Vitro Techniques; D008564:Membrane Potentials; D051379:Mice; D009045:Motor Endplate / Q000502:physiology*; D009410:Nerve Degeneration; D009469:Neuromuscular Junction / Q000502:physiology*; D009435:Synaptic Transmission