Functional status of the regenerated chorda tympani nerve as assessed in asalt taste discrimination task

We tested whether the recovered ability of rats to discriminate NaCl from K Cl after chorda tympani nerve transection (CTX) is causally linked to nerve regeneration or some other compensatory process. Rats were presurgically t rained in an operant NaCl vs. KCl discrimination task. Rats with regenerate d nerves, histologically confirmed by anterior tongue taste pore counts and tested 62 days after CTX (CTX-62R; n = 5), performed as well as those test ed 62 days after sham surgery (ham-Ga; n = 5), but both of these groups ini tially performed slightly worse than animals tested 7 days after sham surge ry (Sham-7; n = 4). Performance of rats tested either 7 (CTX-7P; n = 5) or 62 (CTX-62P; n = 4) days after CTX in which nerve regeneration was prevente d was severely disrupted. Adulteration of the stimuli with amiloride, an ep ithelial sodium channel blocker, impaired discrimination performance in a s imilar dose-dependent manner in the Sham-7 (n = 2), Sham-62 (n = 5), and CT X-62R (n = 5) groups, suggesting that the functional status of the amilorid e-sensitive transduction pathway returns to normal in rats with regenerated chorda tympani nerves. Performance of CTX rats without regenerated nerves (CTX-7P, n = 2; CTX-62P, n = 4) was further degraded by amiloride treatment , suggesting that taste receptors innervated by other nerves are sensitive to amiloride. In conclusion, nerve regeneration is an essential component u nderlying full recovery of salt discrimination function after CTX.