Neurotrophin-4 dependency of intraepithelial vagal sensory nerve terminals that selectively contact pulmonary NEBs in mice expressing populations of vagal myelinated afferents, only one is distinctly reduced in NT-4 deficient mice, suggesting the involvement of NTs. In view of the growing evidence for the involvement of NTs in neuronal plasticity associated with airway diseases, pulmonary NEBs innervated by NT-sensitive vagal afferents may play a significant role.