SALT DISCRIMINABILITY IS RELATED TO NUMBER OF REGENERATED TASTE-BUDS AFTER CHORDA TYMPANI NERVE-SECTION IN RATS

Transection of the chorda tympani nerve (CTX) impairs taste-guided discrimination of NaCl from KCl in rats. We wanted to determine whether this discrimination recovers after chorda tympani regeneration. Experiment 1 showed that few taste buds regenerated 14 days after CTX, whereas substantial regeneration occurred 42 days after surgery. Experiment 2 demonstrated that rats trained before CTX could clearly discriminate the two salts when tested starting 49 days after surgery, whereas rats tested starting 8 days after surgery were severely impaired in this task. Rats tested starting 28 days after CTX were unimpaired, moderately impaired, or severely impaired on the discrimination task. Overall, discrimination performance was significantly related to the number of regenerated taste buds. Unilaterally transected rats tested shortly after surgery were nearly as competent as controls. These results indicate that rats can recover the ability to discriminate NaCl from KCl after regeneration of anterior tongue taste buds.