Journal of Neuroscience, Vol 11, 1309-1315, Copyright © 1991 by Society for Neuroscience
Synaptic transmission in decentralized axons of rock lobster
I Parnas, J Dudel and HL Atwood
Otto Loewi Center for Cellular and Molecular Neurobiology, Hebrew University, Jerusalem, Israel.
Axons of the lobster deep abdominal extensor muscles were cut, and the
resulting effects on their synaptic properties were observed. Decentralized
axons continued to conduct action potentials and to release transmitter for
at least a year after the cut. In controls, the single quanta were brief,
and their decay phase could be fit by a single exponent, with a time
constant of about 2 msec. Quanta of "cut axons" were slower, and their
decay phase could not be fit by a single exponent. At midamplitude, the
duration of the cut-axon quanta varied between 1.6 and 5.8 msec, as opposed
to 0.6-2.8 msec in controls. Synaptic delay histograms were taken as a
measure of time course of evoked release. In controls, evoked release
lasted less than 10 msec at 14 degrees C. In cut axons, release lasted up
to 10 times longer. The duration of release was not affected by
tetrodotoxin, membrane depolarization, or hyperpolarization. It appears
that the basic mechanism that controls the time course of evoked release is
altered in degenerating terminals.