Journal of Neuroscience, Vol 4, 274-280, Copyright © 1984 by Society for Neuroscience
Steroid regulation of neuronal death in the moth nervous system
JW Truman and LM Schwartz
The emergence of the adult Manduca sexta moth is followed by the programmed
degeneration of about 50% of the insect's abdominal interneurons and
motoneurons. Neurons in implanted ganglia undergo degeneration in concert
with neurons of the host, thereby indicating that a hormonal cue is
important. The neuronal death follows the normal decline in the levels of
the steroid hormones, ecdysteroids, that occurs at the end of
metamorphosis. Manipulations that cause a precocious ecdysteroid decline
result in an early death of the neurons. Also, prolongation of the
ecdysteroid titer extend the life of the neurons. By properly timed steroid
application it was possible to dissociate the neuronal degeneration from
the behavioral events and muscle degeneration that also occur at emergence.
Also the stereotyped sequence of death among identified motoneurons could
be stopped at various points in the sequence by the carefully timed
application of steroid. It was concluded that the signal for neuronal death
was the withdrawal of ecdysteroids at the end of metamorphosis and that the
death was probably a direct response of the individual neurons to the
hormone withdrawal.
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