NERVE GROWTH-FACTOR REGULATES THE EXPRESSION OF BRAIN-DERIVED NEUROTROPHIC FACTOR MESSENGER-RNA IN THE PERIPHERAL NERVOUS-SYSTEM

Neurotrophins are profound regulators of neuronal survival in the deve loping peripheral nervous system and are synthesized by peripheral neu rons themselves both during development and in maturity. Neuronal neur otrophin expression may be importantly related to survival of mature n eurons, both in normal and pathological states. We show here that brai n-derived neurotrophic factor (BDNF) gene expression in dorsal root ga nglia is strongly stimulated in vivo by another neurotrophin, nerve gr owth factor (NGF). Furthermore, colocalization studies show that many BDNF-expressing sensory neurons also express trk A, the high-affinity NGF receptor. These results demonstrate a novel regulatory mechanism f or neurotrophin gene expression and suggest a paracrine function for n eurotrophins in mature animals.