help needed

[HUIWEN XIE]

It has been known that spontaneous and/or evoked activity influences or
regulates spinal motoneuron development. However, as I understand, the effect is
mediated by neurotrophic factors. For example, the increased motoneuron survival
during naturally occurring cell death by blocking neuromuscular activity with
TTX is due to the increased production of neurotrophic factors by muscle fiber,
vice versa. What I am wondering is that whether these activities themselves have
direct effect on motoneuron development and whether the activity of primary
afferents has the same effect, since during embryonic stage,DRG cells are very
active. Any comments and/or specific references are very welcome.
Thanks!