Mr. Bennett et al., QUANTAL COMPONENTS OF SPONTANEOUS EXCITATORY JUNCTION POTENTIALS AT VISUALIZED VARICOSITIES, Journal of the autonomic nervous system, 56(3), 1996, pp. 161-174
The electrical signs of spontaneous transmitter release were recorded
with an extracellular electrode from single visualized sympathetic var
icosities on the mouse vas deferens. Ultrastructural examination of th
ese varicosities with the electron microscope showed that they formed
close-contacts with smooth muscle cells. Amplitude-frequency histogram
s of the spontaneous excitatory junction potentials (SEJPs) were const
ructed in order to determine the statistical nature of spontaneous tra
nsmitter release from a varicosity. SEJP histograms often possessed se
veral peaks, Statistical tests showed that these were separate modes i
n the histograms indicating that the SEJPs were composed of subunits.
The SEJP histograms were described by a mixture of distributions in wh
ich the components were identified as quanta and there was a Poisson r
elease of quanta. The second mode in the SEJP histograms was sometimes
twice that of the first mode but generally greater, suggesting a pote
ntiation of the effects of one quantum released nearly simultaneously
with another quantum. The components in the SEJP histograms were well
fitted by either a Gaussian or a gamma distribution indicating that th
e quantum of transmitter could be described as a Gaussian or gamma var
iate.