Immunohistochemical studies on neuron-specific enolase in developing rat vallate papillae.

The detailed morphology of the nerve fibers and the taste bud cells in developing vallate papillae of the rat tongue was investigated utilizing the immunoperoxidase technique to detect neuron-specific enolase (NSE). For convenience of description, five stages of development were defined: Stage 1, the fifteenth and the sixteenth embryonic day (E15-E16): NSE like immunoreactive (NSE-) nerve fibers, with some random arborization, appeared around the median lingual sulcus at the base of the tongue; Stage 2 (E16-E17): NSE-nerve fibers invading the central core of newly formed vallate papilla and underlying the apical epithelium of the papilla; Stage 3 (E18-E21): round-shaped undifferentiated NSE-taste bud cells appearing in the apical epithelium; Stage 4, the first day of postnatal age (P1): NSE-taste bud cells migrated to the side epithelium, lining the gutter beneath which the nerve plexus formed during E18-E21, and extended cytoplasmic process toward the surface and/or the basal lamina; Stage 5 (P3-P5): NSE-nerve fibers and spindle-shaped NSE-taste bud cells with a typical figure of taste bud cells appeared in newly formed taste buds in the side epithelium, lining the gutter. The sequential topographic development of nerve preceding NSE-taste bud cells in precise morphological locations, suggests that the ingress of precursor NSE-taste bud cells and their subsequent differentiation are contingent upon initial neural derived ontologic signals.