Transecting the gustatory branches of the facial nerve impairs NH4Cl vs. KCl discrimination in rats

Ammonium and potassium chloride share a common taste quality and an amiloride-insensitive route of transduction. An amiloride-sensitive pathway might also be partially activated by these salts, although very few studies have reported effects of amiloride on nonsodium salt perception. This experiment was designed to determine 1) whether rats could discriminate KCl from NH4Cl and, if discrimination was evident, whether performance was impaired with 2) amiloride or 3) gustatory nerve transection. Rats were trained to discriminate KCl from NH4Cl (n = 8) and NaCl from NH4Cl (n = 8). Amiloride (100 muM) impaired NaCl vs. NH4Cl but not KCl vs. NH4Cl performance, whereas both groups showed significant impairments after transection of the chorda tympani (CT) and greater superficial petrosal (GSP) branches of the facial nerve. This suggests that rats can discriminate between KCl and NH4Cl and that this discrimination does not rely on an amiloride-sensitive mechanism but does depend on the CT and/or GSP nerves. This experiment supports the hypothesis that the facial nerve is important for salt taste recognition and discrimination.