Fig. 5. PGP, GAP, CGRP, and gustducin (Gust.) immunoreactivity in the tongue and palate of wild-type (wt) and BDNF-transgenic (tg) mice at E19. A, Circumvallate papillae are well developed and well innervated in wild-type mice, and an extensive nerve plexus is observed within the papillae and surrounding the lateral trench wall epithelium. Superior surface taste buds are well developed and differentiated, as well as richly innervated (filled arrow). CPs are also well developed and well innervated (asterisks). Nerve bundles are directed toward the CPs and innervate them. B, Circumvallate papillae in BDNF-transgenic mice have distorted morphology and are underdeveloped. The (gustatory) nerve plexus within the papillae as well as the superior surface taste buds are missing. Nerve bundles (open arrows) are however directed toward the CPs (asterisks). C–H, Consecutive sections of circumvallate papillae from wild-type and BDNF-transgenic mice reacted with antibodies to PGP, GAP, and CGRP.C, D, Superior surface taste buds are well innervated (filled arrows). Nerve fibers are also observed in trench wall epithelium (open arrows).E, CGRP-positive fibers (i.e., somatosensory) in wild-type mice are thin and contain varicosities, and are found in association with the papilla and CPs.F–G, In transgenic mice, PGP- and GAP-positive fibers (open arrows) are innervating CPs. There is a severe reduction of subepithelial nerve plexus underlying the gustatory epithelium, corresponding to the loss of vallate taste buds. H, CGRP-positive fibers (open arrows) are found in association with CPs, and a few fibers are found in the midportion of the papilla. I, In wild-type mice, gustducin-positive palatal taste buds (filled arrow) are found posteriorly at the level of circumvallate papillae. Gustducin immunoreactivity is more intense in the palatal taste cells (which might represent the maturity of palatal taste cells) than in vallate taste buds. Nevertheless, positive taste cells are also found in the circumvallate papillae (open arrows). Theinset is a higher magnification of the area marked witharrowheads. J, Only palatal (and laryngeal, data not shown) taste buds are gustducin-positive in BDNF-transgenic mice (filled arrow). No gustducin immunoreactivity is observed in the circumvallate papillae.K, Higher magnification of the gustducin-immunoreactive taste cells marked with a filled arrow inI. L, Higher magnification of a gustducin-immunoreactive taste bud from BDNF-transgenic mice. Cells are clearly elongated. M, N, Palatal taste buds (open arrows) at “geschmacks-streifen” in BDNF-transgenic mice are well innervated, and taste cells are PGP-positive. The elongated shape of the taste cells is clearly visible. Scale bars: A, B, 50 μm;C–J, 100 μm; M,N, 200 μm.