AJP - Cell Physiology, Vol 233, Issue 5 157-C163, Copyright © 1977 by American Physiological Society
Estimates of quantal-release and binomial statistical-release parameters at rat neuromuscular junction
D. F. Wilson
Quantal-release and binomial statistical-release parameters were examined
in the isolated rat diaphragm phrenic nerve preparation. The muscle resting
potentials were reduced by cutting the muscle fibers to prevent muscle
action potentials and contractions. The cutting technique was modified to
allow persistent observation of miniature end-plate potentials (MEPPs) and
end-plate potentials (EPPs) with intracellular recording techniques. Direct
estimates of quantal release were examined and compared with predicted
binomial and Poisson distributions. The results indicate that release is
binomial when the nerve is stimulated with low- or high-frequency stimuli.
The indirect method of estimating quantal release (variance method), which
assumes release is described by a Poisson distribution, seriously
overestimates quantal release. The binomial analysis indicates that the
statistical store is small (less than 90 quanta) and that most of these
quanta are released with each nerve impulse.
