Roper Stephen D
Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
Pflugers Arch. 2007 Aug;454(5):759-76. doi: 10.1007/s00424-007-0247-x. Epub 2007 Apr 28.
The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acid-sensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation.
在过去十年中，味蕾中化学感觉转导的分子机制受到了相当多的关注。因此，我们现在对甜味、苦味和鲜味的味觉机制有了很多了解，并且在咸味和酸味转导方面也迅速取得进展。甜味、苦味和鲜味是由G蛋白偶联受体转导的。咸味可能是由类似于肾组织中发现的上皮钠通道转导的。酸味转导似乎是由作用于酸敏感膜蛋白的细胞内酸化引发的。一旦在味觉细胞中产生味觉信号，随后的步骤包括神经递质的分泌，包括ATP和5-羟色胺。现在人们认识到，对甜味、苦味和鲜味味觉刺激作出反应的细胞不具备突触，而是通过一种不涉及传统囊泡胞吐作用的新机制分泌神经递质ATP。ATP被认为会刺激将味觉信号传递到大脑的初级感觉传入纤维。相比之下，具有突触的味觉细胞在受到味觉刺激时会释放5-羟色胺。5-羟色胺的突触后靶点尚未确定。最后，从受体细胞分泌的ATP也作用于相邻的味觉细胞，刺激它们释放5-羟色胺。这表明在味觉刺激后，哺乳动物味蕾中发生了重要的信息处理和信号编码。
