SPLTRAK Abstract Submission
The innervation of taste buds differs between humans, tree shrews, and mice
Brigit High, Courtney E. Wilson, Ruibiao Yang, Mei Li, Thomas E. Finger
Rocky Mountain Taste and Smell Center: University of Colorado School of Medicine, Aurora, CO, United States

Gustatory nerve fibers innervate mammalian taste buds and express P2X receptors, reflecting the obligate purinergic nature of gustatory transmission. These fibers arise from the facial nerve to innervate the fungiform papillae and from the glossopharyngeal nerve to innervate the circumvallate and foliate papillae. Acetylated tubulin serves as a marker for all nerve fibers, while P2X3 labels gustatory fibers as well as subset of mucosal nerve fibers. We utilized immunohistochemistry with these two markers as well as electron microscopy to compare the patterns of innervation of fungiform and circumvallate papillae of mice, humans and tree shrews (Tupaia belangeri), a member of the Euarchontoglires superorder of mammals whose phylogenetic classification has produced controversy due to it sharing features of both primates and rodents. Although the general pattern of innervation is conserved across all three species, we find increased density of innervation by P2X3-immunoreactive nerve fibers in humans compared to mice and tree shrews. In addition, the nerve fibers in human taste buds appear thicker and more tortuous as compared to mice. Further ultrastructural analysis is necessary to determine whether the details of connectivity in humans differ from those in mice and tree shrews.