RT Journal Article
SR Electronic
T1 Lack of Neurotrophin 3 Causes Losses of Both Classes of Spiral Ganglion Neurons in the Cochlea in a Region-Specific Fashion
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 6213
OP 6225
DO 10.1523/JNEUROSCI.17-16-06213.1997
VO 17
IS 16
A1 Bernd Fritzsch
A1 Isabel Fariñas
A1 Louis F. Reichardt
YR 1997
UL http://www.jneurosci.org/content/17/16/6213.abstract
AB Essential functions of neurotrophin 3 (NT-3) in regulating afferent and efferent innervation of the cochlea have been characterized by comparison of normal and NT-3 mutant mice. NT-3 deficiency has striking, region-specific effects, with complete loss of sensory neurons in the basal turn and dramatic but incomplete neuronal loss in the middle and apical turns. The sensory innervation of inner and outer hair cells was reorganized in mutant animals. Instead of a strictly radial pattern of innervation, the axons of remaining sensory neurons projected spirally along the row of inner hair cells to innervate even the most basal inner hair cells. Innervation of outer hair cells was strongly reduced overall and was not detected in the basal turn. The presence of fibers extending to both inner and outer hair cells suggests that subsets of types I and II sensory neurons survive in the absence of NT-3. Likewise, projections of the cochlea to auditory nuclei of the brainstem were attenuated but otherwise present. Equally striking changes in efferent innervation were observed in mutant animals that closely mimicked the abnormal sensory innervation pattern. Despite these impressive innervation deficiencies, the morphology of the organ of Corti and the development of inner and outer hair cells appeared comparatively normal.