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. 1998 Apr 28;95(9):5347–5350. doi: 10.1073/pnas.95.9.5347

Figure 1.

Figure 1

(A) Schematic drawing of taste nerve crosses and normal taste nerve innervation of the mouse tongue. The normal innervation is shown on the left side of the tongue in A-1. The glossopharyngeal nerve (IX) innervates taste buds in the circumvallate and foliate papillae. The chorda tympani (CT) nerve joins the lingual nerve (L) before entering the tongue and distributes to the anterior two-thirds of the tongue, including a small contribution to the foliate papillae. On the right side in A-1, the CT nerve was cut and the central portion of the CT was rejoined to the peripheral portion of the CT (CTc-CTp). The IXth nerve was cut and the central portion of the IXth was rejoined to the peripheral portion of the Ixth (IXc-IXp). In A-2, the central portion of the CT nerve was sutured to the peripheral part of the IXth nerve (CTc-IXp). In A-3, the central part of the IXth nerve was joined to the peripheral part of the CT nerve (IXc-CTp). (B) Sample recordings of single-fiber responses of the CT nerve (1) and IXth nerve (2) to 0.1 M NaCl and 0.1 M KCl with and without 0.1 mM amiloride. There are two CT units, one large and one small. The larger one showed amiloride inhibition of NaCl responses [amiloride-sensitive (AS) type], but the smaller one did not [amiloride-insensitive (AI) type]. The IX unit was an AI fiber. (C) Distributions of taste neurons with their percentage of control responses to 0.1 M NaCl with 0.1 mM amiloride (control responses to NaCl without amiloride = 100%) in the intact CT (n = 31), intact IX (n = 31), CTc-CTp (n = 29), IXc-IXp (n = 30), CTc-IXp (n = 31), and IXc-CTp (n = 29). In the intact control groups, mean responses (±SD) to NaCl without and with amiloride were 73.4 ± 45.9 and 33.5 ± 23.7 impulses/10 s, respectively, for the CT fibers (mean percent control response, 55.6 ± 38.2%) and 43.6 ± 20.6 and 37.4 ± 16.7 impulses/10 s, respectively, for the IXth fibers (mean percent control response, 89.5 ± 20.2%). There were two groups of taste fibers in the distribution (bimodal in shape, amiloride-sensitive and amiloride-insensitive types) for the intact, regenerated, and cross-regenerated CT nerve, whereas most fibers of the intact, regenerated, and cross-regenerated IXth nerve were amiloride-insensitive, thereby producing unimodal distributions.