Testosterone fails to rescue motoneurons from axotomy-induced death in young rats.

This study was undertaken to determine whether testosterone acting on muscle alone could enhance motoneuron survival after axotomy. Facial nerves were transected unilaterally in 10-day old rats in which androgen receptors were already present in skeletal muscle but not yet developed in motoneurons. Testosterone treatment lessened chromatolysis but failed to reduce neuronal loss which reached more than 50% 2 weeks postaxotomy. The inefficacy of testosterone was attributed to the death of motoneurons before they could re-establish synaptic contact with targets, thereby rendering target-derived trophic substances stimulated by testosterone unable to rescue motoneurons in a timely manner. The present finding is consistent with our hypothesis that functional neuromuscular connectivity is a prerequisite for testosterone to promote neuronal survival.