title: Changes in responsiveness of rat spiral ganglion neurons to neurotrophins across age: differential regulation of survival and neuritogenesis.
abstract: Developmental changes in responsiveness of rat spiral ganglion neurons (SGNs) to neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) were examined using an explant culture system. Spiral ganglion (SG) explants at embryonic Day 18 (E18), postnatal Day 0 (P0), P5, P10 and P20 were cultured with the addition of either NT-3 or BDNF at various concentrations (0.1-100 ng/ml) and analyzed the dose-response characteristics of three parameters: SGN survival, the number of neurites emanating from the explants and the length of neurite extension. In E18 cultures, SGN survival and neurite number were enhanced more strongly by NT-3 than by the BDNF. As the explants became more mature, the effects of NT-3 decreased, whereas those of BDNF increased, peaking at P0. Although the intrinsic capacity of SGNs to produce and extend neurites declined considerably by P20, they still retained the capacity to respond to both NT-3 and BDNF. These temporal patterns in responsiveness of SGNs to neurotrophins correspond well to the expression pattern of the two neurotrophins in cochlear sensory epithelium in vivo and also correlate with the time course of developmental events in SGNs such as cell death and the establishment of mature hair cell innervation patterns.
authors.affiliation: Division of Otolaryngology and Neurosciences, Department of Surgery and Veterans Administration Medical Center, University of California, San Diego School of Medicine, La Jolla, CA 92093, USA.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kondo
authors.forename: Kwang
authors.initials: K
authors.lastname: Pak
authors.forename: Eduardo
authors.initials: E
authors.lastname: Chavez
authors.forename: Lina
authors.initials: L
authors.lastname: Mullen
authors.forename: Sara
authors.initials: S
authors.lastname: Euteneuer
authors.forename: Allen F
authors.initials: AF
authors.lastname: Ryan
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D016501:Neurites / Q000187:drug effects*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D020933:Neurotrophin 3 / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D017475:Receptors, Nerve Growth Factor / Q000096:biosynthesis; D013136:Spiral Ganglion / Q000166:cytology*
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D020933:Neurotrophin 3; D017475:Receptors, Nerve Growth Factor