PT  - JOURNAL ARTICLE
AU  - Faisal N. Zaidi
AU  - Robin F. Krimm
AU  - Mark C. Whitehead
TI  - Exuberant Neuronal Convergence onto Reduced Taste Bud Targets with Preservation of Neural Specificity in Mice Overexpressing Neurotrophin in the Tongue Epithelium
AID  - 10.1523/JNEUROSCI.2517-07.2007
DP  - 2007 Dec 12
TA  - The Journal of Neuroscience
PG  - 13875--13881
VI  - 27
IP  - 50
4099  - http://www.jneurosci.org/content/27/50/13875.short
4100  - http://www.jneurosci.org/content/27/50/13875.full
SO  - J. Neurosci.2007 Dec 12; 27
AB  - A mouse fungiform taste bud is innervated by only four to five geniculate ganglion neurons; their peripheral fibers do not branch to other buds. We examined whether the degree or specificity of this exclusive innervation pattern is influenced by brain-derived neurotrophic factor (BDNF), a prominent lingual neurotrophin implicated in taste receptoneural development. Labeled ganglion cells were counted after injecting single buds with different color markers in BDNF-lingual-overexpressing (OE) mice. To evaluate the end-organs, taste buds and a class of putative taste receptor cells were counted from progeny of BDNF-OE mice crossbred with green fluorescent protein (GFP) (gustducin) transgenic mice. Fungiform bud numbers in BDNF-OE mice are 35%, yet geniculate neuron numbers are 195%, of wild-type mice. Neurons labeled by single-bud injections in BDNF-OE animals were increased fourfold versus controls. Injecting three buds, each with different color markers, resulted in predominantly single-labeled ganglion cells, a discrete innervation pattern similar to controls. Thus, hyper-innervation of BDNF-OE buds involves many neurons innervating single buds, not increased fiber branching. Therefore, both wild-type and BDNF-OE mice exhibit, in fungiform buds, the same, “discrete” receptoneural pattern, this despite dramatic neurotrophin overexpression-related decreases in bud numbers and increases in innervation density. Hyperinnervation did not affect GFP positive cell numbers; proportions of GFP cells in BDNF-OE buds were the same as in wild-type mice. Total numbers of ganglion cells innervating buds in transgenic mice are similar to controls; the density of taste input to the brain appears maintained despite dramatically reduced receptor organs and increased ganglion cells.