The Journal of Cell Biology, Vol 105, 2235-2243, Copyright © 1987 by The Rockefeller University Press
A transient intracellular coupling explains the facilitation of responses in the bioluminescent system of scale worms
JM Bassot
Laboratoire de Bioluminescence, Centre National de la Recherche Scientifique, Gif sur Yvette, France.
Isolated elytra of polynoid worms emit a flash of bioluminescence when
stimulated by an electric shock. With repeated stimulation, hundreds of
flashes can be elicited which, in typical series, exhibit large and
progressive variations. The amount of luminescence emitted by each flash
first increases during a period of facilitation and then decreases
exponentially during a longer period of decay. Through a microscope and
image intensifier, the activity of individual microsources or photosomes
was observed, using their fluorescence as a natural probe, in that its
intensity is a function of the amount of luminescence previously emitted.
Sequential observation showed a progressive and basically intracellular
recruitment that correlated with facilitation. Facilitation and/or
recruitment depended on the frequency of the stimulation. Recruitment
proceeded among the photosomes of each photocyte, beginning with those of
the cell periphery and progressing to those of the center. When the
repetitive stimulation was interrupted and then resumed, the refacilitation
was a function of the duration of the pause, and the pathway of recruitment
duplicated that of the preceding sequence. It therefore appears that,
within a given cell, individual photosomes can be either coupled and
respond to stimulation or uncoupled and quiescent, that the coupled state
has a basic lifetime of about 1 s which can be lengthened by reinforcement,
and that this state must be established in a matter of milliseconds as a
result of the stimulation. In preparing an increased response to a
forthcoming stimulation, coupling acts as a short-term memory.
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