Taste Neurons Consist of Both a Large TrkB-Receptor-Dependent and a Small TrkB-Receptor-Independent Subpopulation |
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Authors: | Da Fei Robin F Krimm |
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Institution: | Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, Kentucky, United States of America.; Baylor College of Medicine, United States of America, |
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Abstract: | Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) are two neurotrophins that play distinct roles in geniculate (taste) neuron survival, target innervation, and taste bud formation. These two neurotrophins both activate the tropomyosin-related kinase B (TrkB) receptor and the pan-neurotrophin receptor p75. Although the roles of these neurotrophins have been well studied, the degree to which BDNF and NT-4 act via TrkB to regulate taste development in vivo remains unclear. In this study, we compared taste development in TrkB−/− and Bdnf−/−/Ntf4−/− mice to determine if these deficits were similar. If so, this would indicate that the functions of both BDNF and NT-4 can be accounted for by TrkB-signaling. We found that TrkB−/− and Bdnf−/−/Ntf4−/− mice lose a similar number of geniculate neurons by E13.5, which indicates that both BDNF and NT-4 act primarily via TrkB to regulate geniculate neuron survival. Surprisingly, the few geniculate neurons that remain in TrkB−/− mice are more successful at innervating the tongue and taste buds compared with those neurons that remain in Bdnf−/−/Ntf4−/− mice. The remaining neurons in TrkB−/− mice support a significant number of taste buds. In addition, these remaining neurons do not express the TrkB receptor, which indicates that either BDNF or NT-4 must act via additional receptors to influence tongue innervation and/or targeting. |
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