By E14.5, chorda tympani fibers have innervated fungiform papillae. Chorda tympani fibers have a stereotypical branching pattern in the tongue (A). A higher magnification view of the area outlined in (A) illustrates that each fiber bundle ends in a distinctive bulb shape known as a neural bud (B, arrows). Neural buds form when gustatory fibers penetrate the epithelium at the surface of a fungiform papilla (C). All papillae appear to be innervated when the image from a portion of a E16.5 tongue following DiI-labeling (D) and the SEM image from the same tongue region (F) are overlaid (E). However, there are some neural buds in locations where no fungiform papillae are present (arrows in E and F).
Krimm BMC Neuroscience 2007 8(Suppl 3):S4 doi:10.1186/1471-2202-8-S3-S4