Introduction

A cross-sensory interaction between gustatory and trigeminal nerves occurs in the anterior tongue. Surgical manipulations have demonstrated that the strength of this relationship varies across development. Capsaicin is a neurotoxin that affects fibers of the somatosensory lingual nerve surrounding taste buds, but not fibers of the gustatory chorda tympani nerve which synapse with taste receptor cells. Since capsaicin is commonly consumed by many species, including humans, the experimental use of this neurotoxin provides a naturalistic perturbation of the lingual trigeminal system. Neonatal or adult rats consumed oral capsaicin for 40 days, and we examined the cross-sensory effect on the morphology of taste buds across development.

Methods

Rats received moderate doses of oral capsaicin, with chronic treatments occurring either before or after taste system maturation. Tongue morphology was examined either 2 or 50 days after treatment cessation. Edema, which has been previously suggested as a cause of changes in capsaicin-related gustatory function, was also assessed.

Results

Reductions in taste bud volume occurred 50 days, but not 2 days post-treatment for rats treated as neonates. Adult rats at either time post-treatment were unaffected. Edema was not found to occur with the 5 ppm concentration of capsaicin we used.

Conclusions

Results further elucidate the cooperative relationship between these discrete sensory systems and highlight the developmentally mediated aspect of this interaction.

Implications

Chronic exposure to even moderate levels of noxious stimuli during development has the ability to impact the orosensory environment, and these changes may not be evident until long after exposure has ceased.

中文翻译：

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发育过程中长期口服辣椒素会导致成年大鼠的味蕾减少。

介绍

味觉神经和三叉神经之间的交叉感觉相互作用发生在前舌中。外科手术表明，这种关系的强度在整个发育过程中是不同的。辣椒素是一种神经毒素，会影响味蕾周围的体感舌神经的纤维，但不会影响与味觉受体细胞突触的味觉性鼓膜鼓动神经的纤维。由于辣椒素通常被包括人类在内的许多物种所消耗，因此这种神经毒素的实验用途为舌三叉神经系统提供了自然的干扰。新生或成年大鼠食用辣椒素40天，我们研究了在整个发育过程中对味蕾形态的交叉感觉效应。

方法

大鼠接受中等剂量的辣椒素口服液，在味觉系统成熟之前或之后进行慢性治疗。停止治疗后2或50天检查舌头形态。还评估了先前被认为是辣椒素相关味觉功能改变的原因的水肿。

结果

对于新生大鼠而言，味蕾量减少发生在治疗后50天，但未在治疗后2天发生。治疗后任一时间的成年大鼠均不受影响。我们使用的辣椒素浓度为5 ppm时未发现水肿发生。

结论

结果进一步阐明了这些离散的感觉系统之间的合作关系，并强调了这种相互作用的发展介导方面。

含意

在发育过程中即使长期暴露于中等水平的有害刺激下，也具有影响口感环境的能力，这些变化可能要等到暴露停止很长时间后才能显现出来。