Long-term alterations in peripheral taste responses to NaCl in adult rats following neonatal chorda tympani transection.

The peripheral taste system of the adult rodent is highly resilient against damage, with morphological, behavioral, and functional recovery evident after regeneration of a transected nerve. If chorda tympani transection (CTX) occurs at early postnatal ages however, the nerve fails to regenerate and effects on tongue morphology and behavior are more severe and longer-lasting compared to adult denervation. To examine whether neonatal CTX induces functional changes in intact nerves, whole-nerve electrophysiology was performed on the glossopharyngeal (GL) and chorda tympani (CT) nerves of adult rats that received CTX at P10. Attenuation of NaCl-elicited GL responses were observed in CTX rats 2 months after surgery, with bilateral denervation causing the largest decreases in responses. When assessed 1 year after neonatal CTX, amiloride-sensitive responses to NaCl in the contralateral CT increased while amiloride-insensitive responses decreased. Responses to other tastants were consistent with control animals. This is the first evidence of long-term functional changes to the peripheral taste system after injury in rats fed a normal diet. This study further characterizes the developing peripheral taste system as highly susceptible to change following neural injury.