Fig. 2.

Activity dependent NMJ maintenance/stabilization. a Two motoneurons with synchronous activity are schematized. A similar activity will allow the synthesis of an equivalent amount of punishment (synaptotoxic factor) and reward (synaptotrophic factor) by both MNs, and their survival. b Inactive MNs will not be induced to produce either punishment or reward signal; the absence of competition for survival factor will allow the maintenance of both MNs. c The stabilization of one out of two MNs axons innervating a similar myofiber will be regulated by the activity: the active MN will synthesis both protective (reward) and punishment signals, that will allow its survival, whereas the inactive MN will receive punishment signals from the neighboring active MN only, that will lead to its elimination. Asynchronous AChR activation allows muscle to selectively destabilize synaptic sites to be eliminated