Mp. Primi et Pgh. Clarke, PRESYNAPTIC INITIATION BY ACTION-POTENTIALS OF RETROGRADE SIGNALS IN DEVELOPING NEURONS, The Journal of neuroscience, 17(11), 1997, pp. 4253-4261
Until recently, the only means by which electrical activity was believ
ed to initiate retrograde signals was via postsynaptic events: modulat
ed synthesis or release of trophic factors, We have evidence in chick
embryos for a presynaptic initiation of retrograde signals from the re
tina 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 embryoni
c day 14 reduce neuron death and prevent lamination in the isthmo-opti
c 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 ter
minals. Alternative possibilities, such as an indirect effect via the
target cells, are ruled out by control experiments, Normally, action p
otentials may lead to a chain of second messenger events in the axon t
erminal that is signaled retrogradely via the transport of a long-live
d second messenger.