Nerve-Target Interactions in the Gustatory System Following Unilateral Chorda Tympani Nerve Section

Abstract

Although much effort has been directed at examining the morphological characteristics of denervated and regenerated taste buds, relatively little is known about the physiology of reinnervated taste cells (Vintschgau and Honigschmied, 1876; Guth, 1957; Fujimoto and Murray, 1970; Cheal and Oakley, 1977; Whitehead et al., 1987). Over 25 years ago, Oakley (Cheal et al., 1977) and colleagues found that some chorda tympani fibers reinnervated fungiform papillae on the gerbil’s anterior tongue in <2 weeks post-sectioning. Studies that examined recovery of taste function following nerve damage (Cain et al., 1996; Cheal et al., 1977; Ninomiya, 1998; Yasumatsu et al., 2003) indicate that regenerated taste nerves generally recover normal function after progressing through a transitional period. Only relatively recently has the impact of environment on the adult regenerating taste system been explored. Regenerating taste receptor cells in adult rats are susceptible to dietary influences (Hill and Phillips, 1994). Sectioning the chorda tympani unilaterally in rats fed a sodium-restricted diet at adulthood resulted in a regenerated nerve that had attenuated responses to sodium salts. Responses to other stimuli were unaffected. In addition, there were other, novel effects. In the same rat, the contralateral, uncut nerve was supersensitive to sodium salts. The supersensitivity developed progressively following an initial