SPLTRAK Abstract Submission
Taste Cell Turnover Regulates Taste Nerve Fiber Complexity
Zachary D. Whiddon & Robin F. Krimm
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY, United States

The continual replacement of taste cells creates interesting questions regarding how the innervating neurons are impacted. Here we ask how the morphology of neuron endings within taste buds is affected when taste cell entry is inhibited and reestablished. Inhibition of sonic hedgehog signaling (Shh) is thought to inhibit taste cell turnover. Consistently, fewer new cells were added to individual taste buds after 10 days (0.591±0.282 (p<0.009, df=5)) and 16 days (1.10±0.802 (p<0.011, df=4)) of Shh inhibitor treatment compared to vehicle treatment (2.64 (±0.643)). Taste bud volume did not decrease significantly after 10 days (p=0.242, df=4), but had decreased by 16 days of treatment (p<0.011, df=4). We next examined how taste nerve fiber extension into the gustatory epithelium is affected by preventing taste cell turnover. In normal taste buds, fibers are most numerous at the base of the bud (in the nerve plexus) with an average of 19.1 (±2.16) fibers present. Number of fibers within this nerve plexus are decreased after 16 and 23 (p=0.008, df=4), but not 10 days of Shh inhibitor (p=0.136). However, 10 days of Shh inhibitor does cause a loss of fibers at higher levels within the taste bud (p=0.036 at 6 µm above the plexus). A finding consistent with loss of higher order branches before elimination of fibers within the nerve plexus at the taste bud base - this a model that we are currently testing. A recovery period of 7 days following 16 days of inhibition restores taste cell entry (5.63 (±1.06)), but does not restore fibers within the plexus. This suggests that recovery of normal branch morphology requires more than 7 days of cell turnover. These results provide evidence for the hypothesis that normal branch morphology within the taste bud is supported by taste cell turnover.