Induction of apoptosis of taste bud cells by denervation and administration of drugs

味觉神经切片使味蕾细胞变性消失，神经再生后，味蕾细胞再生。我们最近（1996）报道了舌咽神经切片诱导小鼠周围乳头味蕾细胞凋亡。由此可见，味觉神经释放的引起味蕾细胞分化和维持味蕾细胞的营养物质可能对味蕾细胞凋亡具有抑制作用。在这项研究中，我们试图检验营养物质的性质。抑制细胞凋亡的Bcl-2和Bcl-x的免疫组化反应显示，上皮细胞和味蕾细胞的各层上皮细胞均呈阳性染色。钾离子载体缬霉素引起细胞质钙浓度升高。在成年dd-小鼠舌周乳头附近粘膜注射缬霉素。石蜡切片用DNA缺口末端标记法原位检测凋亡细胞核。注射缬霉素后20、24 h，味蕾内可见分散阳性细胞核。结果表明，细胞内钙离子含量升高可诱导味蕾细胞凋亡。同时，我们也建立了将该物质注射到周围乳头内的方法。我们正在研究各种生长因子如BDNF和GDNF是否会干扰神经切片后味蕾细胞的凋亡。

Gustatory nerve sectioning causes degeneration and disappearance of taste bud cells and after regeneration of the nerves, the taste bud cells regenerate. We recently (1996) reported that glossophaiyngeal nerve sectioning induced apoptosis of taste bud cells in the mouse circumvallate papillae. Thus, the trophic substance released from gustatory nerves, that causes differentiation and maintains taste bud cells, may have an inhibitory effect on apoptosis of taste bud cells.In this study we tried to examine the nature of the trophic substance. An immunohistochemical reaction for Bcl-2 and Bcl-x, which inhibit apoptosis, revealed positive staining of the epithelial cells in all layers of the epithelium and taste bud cells. Potassium ionophore valinomycin triggers an increase of the cytoplasinic calcium concentration. Valinomycin was injected in the mucosa near the circumvallate papillae in adult dd-mice tongues. Paraffin sections were cut and treated by method of DNA nick end labeling which detects apoptotic nuclei in situ. 20 and 24 h after injection of valinomycin, positive nuclei were scattered in the taste buds. The result shows that a rise in the intracellular content of calcium ion induces apoptosis of taste bud cells. Also we have established the method to inject the substances into the circumvallate papillae. We are examining whether apoptosis of the taste bud cells after nerve sectioning would be interfered by treatment of various kinds of growth factors such as BDNF and GDNF.