Journal of Neuroscience, Vol 14, 2904-2910, Copyright © 1994 by Society for Neuroscience
Functional plasticity of regenerated and intact taste receptors in adult rats unmasked by dietary sodium restriction
DL Hill and LM Phillips
Department of Psychology, University of Virginia, Charlottesville 22903- 2477.
Unilateral chorda tympani nerve sectioning was combined with institution of
a sodium-restricted diet in adult rats to determine the role that
environment has on the functional properties of regenerating taste receptor
cells. Rats receiving chorda tympani sectioning but no dietary manipulation
(cut controls) and rats receiving only the dietary manipulation (diet
controls) had normal responses to a concentration series of NaCl, sodium
acetate (NaAc), and NH4Cl. However, responses from the regenerated nerve in
NaCl-restricted rats (40-120 d postsectioning) to NaCl and NaAc were
reduced by as much as 30% compared to controls, indicating that
regenerating taste receptors are influenced by environmental (dietary)
factors. Responses to NH4Cl were normal; therefore, the effect appears
specific to sodium salts. Surprisingly, in the same rats, NaCl responses
from the contralateral, intact chorda tympani were up to 40% greater than
controls. Thus, in the same rat, there was over a twofold difference in
sodium responses between the right and left chorda tympani nerves. A study
of the time course of the functional alterations in the intact nerve
revealed that responses to NaCl were extremely low immediately following
sectioning (about 20% of the normal response), and then increased
monotonically during the following 50 d until relative response magnitudes
became supersensitive. This function occurred even when the cut chorda
tympani was prevented from reinnervating lingual epithelia, demonstrating
that events related to regeneration do not play a role in the functional
properties of the contralateral side of the tongue.(ABSTRACT TRUNCATED AT
250 WORDS)