Regeneration of taste buds after reinnervation by peripheral or central sensory fibers of vagal ganglia

Abstract

Denervation causes the degeneration and disappearance of taste buds in the rat's vallate papilla. Buds will, however, reappear after reinnervation by the glossopharyngeal (self-reinnervation), vagus, or chorda tympani nerves. In all previous reinnervation studies, the anastomosis of the reinnervating nerve was performed distal to the sensory ganglia, that is, with peripheral fibers of the ganglia. The present experiment was performed to determine whether buds would reappear after reinnervation by central fibers of the gustatory ganglia. The vallate papilla of adult male rats was studied after denervation and after reinnervation by peripheral (superior and nodose) or central (nodose) sensory fibers of the vagus nerve. All taste buds disappeared from the papilla within 2 weeks after denervation and, in the absence of innervation, none reappeared. Buds were found, however, 5 months after reinnervation by peripheral or central sensory fibers of the vagus nerve. The regenerated buds were found only in their normal location in the trench walls, and not in the epithelium on the top of the papilla or in the epithelium surrounding it. Although more buds were present after peripheral than after central reinnervation, the results demonstrate that either peripheral or central sensory fibers of gustatory ganglia can cause taste bud regeneration. Despite the known morphological and physiological differences between peripheral and central fibers of gustatory sensory ganglia, each can exert a trophic influence sufficient to cause bud regeneration.