EVIDENCE THAT BRAIN-DERIVED NEUROTROPHIC FACTOR IS A TROPHIC FACTOR FOR MOTOR NEURONS INVIVO

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) act upon populations of neurons that express specific receptors. The present study demonstrates that BDNF rescues motor neurons from degeneration and may also play a role in the normal physiology of these cells. BDNF is expressed in the local environment and in muscle targets of motor neurons; muscle expression is up-regulated by denervation. The alpha motor neurons express the gene encoding p145trkB, a receptor involved in BDNF signal transduction, whereas a subset of motor neurons express p75NGFR. BDNF is transported selectively to a motor neurons from skeletal muscles. Finally, BDNF prevents motor neuron death in the axotomized facial nucleus of the neonatal rat. The effects of BDNF on motor neurons raise the possibility that some neurotrophins may be useful in treating patients with motor neuropathies and amyotrophic lateral sclerosis.