Taste neurons are functionally and genetically diverse, but their morphological diversity remains completely unexplored. Using sparce cell genetic labeling, we provide the first reconstructions of peripheral taste neurons. The branching characteristics across 96 taste neurons show surprising diversity in their complexities. Individual neurons had 1 to 17 separate terminal arbors entering between 1 to 7 taste buds, of which 18 neurons also innervated non-taste epithelia. Cluster analysis separated the neurons into four groups according to branch complexity. The primary difference between clusters was the amount of nerve fiber within the taste bud available to contact receptors cells, which implies variation in the number of receptor cells providing input across neurons. Consistently, we found that the maximum number of taste receptor cells capable of providing convergent input onto individual gustatory neurons varied with a range of 1-22 receptor cells. Thus, differences in branching characteristics across neurons indicate that some neurons likely receive input from a larger number of receptor cells than other neurons (differential convergence). By dividing neurons into two groups based on the type of receptor cell most contacted, we found that neurons contacting primarily sour transducing receptor cells were more heavily branched than those contacting primarily sweet/bitter transducing taste receptor cells. This suggests that neuron morphology differs across functional taste quality. However, the considerable remaining variability within each group suggests differential convergence within each functional taste quality.
bioRxiv Subject Collection: Neuroscience