Neurons in the geniculate ganglion provide sensory innervation to: 1) taste buds on the anterior region of the tongue, via the chorda tympani nerve; 2) taste buds on the incisive papilla and the soft palate, via the greater superficial petrosal nerve; and 3) the skin near the ear via a cutaneous nerve. Preliminary studies in our laboratory showed that three high affinity neurotrophin receptor tyrosine kinases (trkA, trkB and trkC) are found in neurons of the geniculate ganglion. The ligands for these receptors are a family of secreted neurotrophic factors: trkA binds Nerve Growth Factor, trkB binds Brain-Derived Neurotrophic Factor and Neurotrophin-4, and trk C binds Neurotrophin-3. In pilot studies on identified single neurons of the rat geniculate ganglion we have found that they can be divided into subsets according to the trk genes they express. Moreover, we have evidence suggesting that trk expression by rat geniculate ganglion neurons changes during development. This research will test two hypotheses: 1) The division of geniculate ganglion neurons into sub-populations based on differences in trk gene expression is related to one or more of the following: a) the projection of 3 main nerve branches from the ganglion, b) the taste and other modalities associated with neurons in the geniculate ganglion, or c) possible differences in central projections of the neurons. We shall use tracer molecules and electrophysiology to identify specific neurons, and subject these to RNA amplification and PCR methodology to look for functional correlates of the differences in trk expression. Hypothesis 2: The changes in trk gene expression in geniculate ganglion neurons reflect major developmental events, such as axon outgrowth, innervation of the peripheral target tissue, naturally occurring cell death, or innervation of the central target. We shall use in vitro and in vivo methods to relate changes in trk expression during development to other major developmental events.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
1R01DC004837-01
Application #
6322226
Study Section
Integrative, Functional and Cognitive Neuroscience 8 (IFCN)
Program Officer
Davis, Barry
Project Start
2001-03-01
Project End
2006-02-28
Budget Start
2001-03-01
Budget End
2002-02-28
Support Year
1
Fiscal Year
2001
Total Cost
$285,180
Indirect Cost
Name
Northwestern University at Chicago
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
City
Evanston
State
IL
Country
United States
Zip Code
60201
Weiler, Elke (2005) Postnatal development of the rat vomeronasal organ. Chem Senses 30 Suppl 1:i127-8
Carr, V McM; Sollars, S I; Farbman, A I (2005) Neuronal cell death and population dynamics in the developing rat geniculate ganglion. Neuroscience 134:1301-8
Farbman, Albert I; Guagliardo, Nick; Sollars, Suzanne I et al. (2004) Each sensory nerve arising from the geniculate ganglion expresses a unique fingerprint of neurotrophin and neurotrophin receptor genes. J Neurosci Res 78:659-67
Farbman, Albert I (2003) Neurotrophins and taste buds. J Comp Neurol 459:9-14