Volume 17, Number 11,
Issue of June 1, 1997
pp. 4253-4261
Copyright ©1997 Society for Neuroscience
Presynaptic Initiation by Action Potentials of Retrograde Signals
in Developing Neurons
Received Jan. 14, 1997; revised Feb. 24, 1997; accepted March 7, 1997.
Marie-Pierre Primi and
Peter G. H. Clarke
Institut de Biologie Cellulaire et de Morphologie, Université
de Lausanne, 1005 Lausanne, Switzerland
Until recently, the only means by which electrical activity
was believed to initiate retrograde signals was via postsynaptic events: modulated synthesis or release of trophic factors. We have
evidence in chick embryos for a presynaptic initiation of retrograde
signals from the retina to the isthmo-optic nucleus, which is known to
undergo 55% neuron death between embryonic days 12 and 17 and to
become laminated during this period. Intraocular injections of
saxitoxin just before embryonic day 14 reduce neuron death and prevent
lamination in the isthmo-optic nucleus within as few as 6 hr. We show
that these rapid effects are attributable to the direct action of
saxitoxin on the isthmo-optic terminals. Alternative possibilities,
such as an indirect effect via the target cells, are ruled out by
control experiments. Normally, action potentials may lead to a chain of
second messenger events in the axon terminal that is signaled
retrogradely via the transport of a long-lived second messenger.
Key words:
chicken embryo;
electrical activity;
isthmo-optic
nucleus;
retrograde signal;
neuronal death;
nervous system;
brain;
development