Changes of gustatory system through life time

为阐明味觉系统随生命周期的变化，对大鼠进行了组织学和电生理实验。对鼓索神经支配的舌前部进行组织学观察，结果表明：1周龄时成熟味蕾中有味孔的比例仅为9%，3周龄时为81.3%。记录鼓索神经的综合反应表明，1周龄的有孔的味蕾与成年大鼠一样，对氯化钠、盐酸和奎宁-盐酸有反应，这表明这些相对年轻的味蕾对这三种刺激功能成熟，但1周龄时对各种糖的反应幅度比成年大鼠小，3周龄时达到最大，然后随着年龄的增长逐渐减弱。此外，不同糖类之间的交叉适应实验、对舌头的链霉蛋白酶-E处理的效果、对糖的开关反应的相关性分析的结果表明，糖反应的质变在3周后仍在继续。这些结果表明，大鼠鼓索神经在出生后发育过程中，糖的味觉加工发生了功能变化。

CHANGES OF GUSTATORY SYSTEM THROUGH LIFE TIME.In order to clarify changes of gustatory system through life time, histological and electrophysiological experiments were performed in the rat. Histological examination on the anterior tongue innervated by chorda tympani nerve showed that the ratio of matured taste buds which possess a taste pore were only 9% of all taste buds observed at 1 week of postnatal age, and 81.3% at 3 weeks of age. Recording integrated responses from the chorda tympani nerve reveals that taste buds with a pore at 1 week of age responded to NaCl, HCl, and quinine-HCl as well as in adult rats, which suggests that these relatively young taste buds are matured functionally for these three stimuli.However, the response magnitudes for various sugars at 1 week of age were smaller compared to those in the adult rat, reached to the maximum at 3 weeks of age, then decreased gradually with age. Also, results from the experiment of cross-adaptation among different sugars, effects of pronase-E treatment of the tongue, analysis of correlation between on- and off-responses to sugars, showed that qualitative changes for sugar responses continues after 3 weeks of age. These results suggest that functional changes occur in the gustatory processing of sugars during postnatal development in the rat chorda tympani nerve.