Neurotrophic factors promote the maturation of developing sensory neurons before they become dependent on these factors for survival

We have studied the early development of chicken embryo sensory neurons in culture before they become dependent on neurotrophic factors for survival. During this period, they undergo a distinct change in morphology: initially they have small, spindle-shaped, phase-dark cell bodies, which become spherical and phase bright and extend long neurites. Although this maturational change occurs in isolated cells grown in chemically defined medium, it is accelerated by brain-derived neurotrophic factor (BDNF) or neurotrophin-3 and is retarded by antisense oligonucleotides that inhibit expression of the common, low affinity neurotrophic factor receptor (gp75^NCFR) and by antisense BDNF oligonucleotides. We conclude that neurotrophic factors play a role in the earliest stages of sensory neuron development and suggest that they operate by an autocrine mechanism at this time.