BDNF is required for the normal development of taste neurons in vivo.

The vallate gustatory epithelium of neonatal trkB null mutant mice (-/-) lacked innervation. This prompted the evaluation of null mutant mice corresponding to the three neurotrophin ligands for tyrosine kinase receptor B (TrkB): brain-derived neurotrophic factor (BDNF), neurotrophin (NT)3, NT4. The vallate gustatory epithelium of nt3-/- mice and of nt4-/- mice appeared normal. Only bdnf-/- mice had a vallate papilla that was stunted, sparsely innervated, and lacked up to 98% of its taste buds. All three defects persisted. For example, the vallate papilla of 12-day-old bdnf-/- mice remained markedly less well innervated than the vallate of 7-day-old or newborn bdnf+/+ mice. The foliate taste papillae of neonatal bdnf-/- mice had similar defects. We conclude that the normal development of taste neurons requires BDNF.