Expression and role of neurotrophic factors in taste bud cells.

神经营养因子影响中枢和外周神经元的存活和维持。用免疫组织化学方法检测正常小鼠耳缘乳突味蕾细胞是否表达胶质细胞源性神经营养因子、神经营养因子3、神经营养因子4及其受体GFRα1、TrkC和TrkB。通过对它们和NCAM、PGP9.5或Gustducin的双重免疫染色，我们还试图确定哪种类型的味蕾细胞表达GDNF、NT3、NT4或它们的受体，因为据报道，NCAM在类型III的细胞中表达PGP9.5，在一些类型的II细胞中表达，在一些类型11的细胞中表达Gustducin。正常味蕾细胞表达GDNF、NT3、NT4、GFα1和TrkB，但不表达TrkC。免疫组织化学双重染色后的激光共聚焦显微镜观察显示，味蕾中的GDNF1和NT3免疫反应细胞几乎不与抗NCAM或抗PGP9.5抗体反应，但可与抗Gustduan抗体染色。另一方面，几乎所有抗PGP9.5或抗胃泌素免疫反应的细胞都表达NT3、GFRα1和TrkB。因此，味蕾细胞中的GDNF3、NT4免疫反应阳性细胞不包括III型细胞，而是胃泌素免疫反应阳性的II型细胞；另一方面，NT3、GFRTrk1和αB免疫阳性细胞包括II型和III型细胞，可能还包括I型细胞。

Neurotrophic factors affect the survival and maintenance of central and peripheral neurons. Using an i m m unocytochemical method, we examined whether the taste bud cells in the circumvallate papillae of normal mice expressed GDNF (Glial cell line-derived neurotrophic factor), NT3 (Neurotrophin3), NT4 (Neurotrophin4), and their GFR α 1, TrkC, and TrkB receptors. Using double immunostaining for either of them and NCAM, PGP9.5, or gustducin, we additionally sought to determine what type of taste bud cells expressed GDNF, NT3, NT4, or their receptors, because NCAM is reported to be expressed in type-III cells, PGP9.5, in type-III and some type-II cells, and gustducin, in some type-11 cells. Normal taste bud cells expressed GDNF, NT3, NT4, GFα1, and TrkB, however they did not express TrkC.Confocal laser scanning microscopic observations after double immunostaining showed that almost none of the GDNF- and NT3-immunoreactive cells in the taste buds were reactive with anti-NCAM or anti-PGP9.5 antibody, but could be stained with anti-gustduan antibody. On the other hand, almost all anti-PGP9.5- or anti-gustducin-irnmunoreactive cells were positive for NT3, GFRα1, and TrkB. Thus, GDNF- and NT4-immunoreacvtive cells did not include type-III cells, but type-II cells, which are gustducin-immunoreactive; on the other hand, NT3-, GFR α 1-, and TrkB-immunoreactive cells included type-II and -IIIcells, and perhaps type-I cells.We conclude that GDNF, NT3, NT4 in the taste bud cells may exert trophic actions on type-I, - II and -III cells by binding to their GFRα1 and TrkB receptors.