B. Walmsley, INTERPRETATION OF QUANTAL PEAKS IN DISTRIBUTIONS OF EVOKED SYNAPTIC TRANSMISSION AT CENTRAL SYNAPSES, Proceedings - Royal Society. Biological Sciences, 261(1361), 1995, pp. 245-250
At some synaptic connections in the central nervous system, amplitude
distributions of evoked synaptic currents exhibit surprisingly sharp a
nd regularly spaced peaks. At these connections, detailed analysis of
the peaks has led to the proposal that the 'quantal' synaptic current
displays very little variability, not only at a release site, but also
between release sites. In this study the latter hypothesis has been t
ested using simulations of evoked transmission. In contrast with previ
ous conclusions, these simulations demonstrate that the experimental o
bservation of regularly spaced peaks in amplitude distributions of syn
aptic currents is compatible with large underlying differences in the
synaptic current amplitudes between release sites. The simulations als
o reveal that quantal analysis based entirely on the observation and a
nalysis of regularly spaced peaks in evoked synaptic current amplitude
distributions, cannot be used with confidence to estimate presynaptic
release probabilities, 'quantal' current amplitudes at each release s
ite, or the total number of available release sites. This problem may
be a confounding factor in determining whether pre- or postsynaptic ch
anges underlie alterations in synaptic efficacy, such as occurs during
long term potentiation.