Functions and species differences of softpalate taste buds in mammals

味蕾中几乎所有IP3R3阳性细胞(96.7%)表达Gustducin，而菌状乳头(FF)和环状乳头(CV)中表达Gustducin的细胞分别为42.4%和60.1%。为了证实Gustducin在味觉传导中的广泛作用，我们记录了Gustducin-KO小鼠三种主要味觉神经的电生理反应，并比较了不同神经的反应特性。与大鼠的免疫组织化学结果一致，Gustducin-KO小鼠的岩浅大神经(GSP)对甜味和苦味刺激的神经反应显著降低。与GSP相反，鼓索神经(CT)和舌咽神经(GL)对甜味和苦味刺激的反应分别降低。GUSTDEIN和IP3R3免疫组织化学结果显示，91.1%的表达IP3R3的细胞呈GUSTDEIN阳性。这些结果d…通过原位杂交和免疫组织化学方法检测了味蕾基本细胞标记物Shh、proxi和Mashi在小鼠胚胎中的表达。从Shh表达开始，Proxi和Shh在舌前部(E12.5)和软腭区(E14.5)呈点状共表达，提示味蕾的基底细胞和胚胎中Shh的表达部位具有共同的特征。在这两个区域，Mashi的表达都落后于Shh和Proxi的表达约2天。在Mashi表达开始之前，神经到达表达Shh的上皮细胞。这些结果表明味蕾中的基底细胞的分化开始不依赖于神经。我们用免疫组织化学和原位杂交的方法分析了CT和GSP交叉再生诱导的大鼠和小鼠味蕾的再生。结果表明，不同神经供应条件下再生后的SP和FF中Gustducin和IP3R3的共表达不依赖于神经，而依赖于上皮。这一结果表明，在交叉再生后，仍然存在相同的功能差异。较少

Gustducin was expressed in almost all (96.7%) IP3R3-expressing cells in taste buds of the soft palate (SP),whereas gustducin-positive cells were 42.4% and 60.1 % of IP3R3-expressing cells in the fungiform (FF) and circumvalate (CV) papillae, respectively. To confirm the broad role of gustducin in the taste transduction on the SP, responses from three major gustatory nerves in gustducin-KO mice were recorded electrophysiologically and the response properties were compared among the nerves. In consistent with the immunohistochemical results in the rat, nerve responses to both sweet and bitter stimuli were markedly reduced in the greater superficial petrosal nerve (GSP) of gustducin-KO mice. In contrast to the GSP, the chorda tympani nerve (CT) and the glossopharngeal nerve (GL) showed reduced responses to sweet and bitter stimuli, respectively. Immunohistochemistry of gustducin and IP3R3 in mice showed that 91.1% of IP3R3-expressing cells in the SP was gustducin positive. These results d … More emonstrate that gustducin is involved in the different lines of the taste-signaling pathway depending on the taste cell differentiation.To examine the embryonic development of the basal cells, the expression of the basal cell markers of taste buds (Shh, Proxi and Mashi) was determined in the mouse embryo by in situ hybridization and immunohistochemistry. Proxi was co-expressed with Shh from the beginning of Shh expression in a punctate pattern on the anterior tongue (E1 2.5) and soft palatal region (E14.5),suggesting that the basal cells of taste buds and Shh-expressing spots in embryos share common features. Mashi expression lagged behind the expression of Shh and Proxi by approximately 2 days in both regions. Nerves reached the epithelium expressing Shh slightly before the onset of Mashi expression. These results suggest that the differentiation of the basal cells in the taste bud starts nerve-independently.We analyzed regenerated taste buds induced by cross-regeneration of CT and GSP in rats and mice using immunohistochemistry and in situ hybridization. The results showed that the gustducin and IP3R3 co-expression between in the SP and FF after the regeneration with the different nerve supply were not depend on the nerve but on the epithelium. This result suggests that the same functional difference still remain after the cross-regeneration. Less