Maeda Naohiro, Ohmoto Makoto, Yamamoto Kurumi, Kurokawa Azusa, Narukawa Masataka, Ishimaru Yoshiro, Misaka Takumi, Matsumoto Ichiro, Abe Keiko
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Monell Chemical Senses Center, Philadelphia, PA, USA.
Neurosci Lett. 2016 Mar 23;617:46-51. doi: 10.1016/j.neulet.2016.01.050. Epub 2016 Feb 5.
Taste cells release neurotransmitters to gustatory neurons to transmit chemical information they received. Sweet, umami, and bitter taste cells use ATP as a neurotransmitter. However, ATP release from sour taste cells has not been observed so far. Instead, they release serotonin when they are activated by sour/acid stimuli. Thus it is still controversial whether sour taste cells use ATP, serotonin, or both. By reverse transcription-polymerase chain reaction and subsequent in situ hybridization (ISH) analyses, we revealed that of 14 serotonin receptor genes only 5-HT3A and 5-HT3B showed significant/clear signals in a subset of neurons of cranial sensory ganglia in which gustatory neurons reside. Double-fluorescent labeling analyses of ISH for serotonin receptor genes with wheat germ agglutinin (WGA) in cranial sensory ganglia of pkd1l3-WGA mice whose sour neural pathway is visualized by the distribution of WGA originating from sour taste cells in the posterior region of the tongue revealed that WGA-positive cranial sensory neurons rarely express either of serotonin receptor gene. These results suggest that serotonin receptors expressed in cranial sensory neurons do not play any role as neurotransmitter receptor from sour taste cells.
味觉细胞向味觉神经元释放神经递质，以传递它们接收到的化学信息。甜味、鲜味和苦味味觉细胞使用三磷酸腺苷（ATP）作为神经递质。然而，迄今为止尚未观察到酸味味觉细胞释放ATP。相反，当它们被酸味/酸性刺激激活时会释放血清素。因此，酸味味觉细胞是使用ATP、血清素还是两者兼用仍存在争议。通过逆转录聚合酶链反应及随后的原位杂交（ISH）分析，我们发现，在14个血清素受体基因中，只有5-HT3A和5-HT3B在味觉神经元所在的颅感觉神经节的一部分神经元中显示出明显/清晰的信号。在pkd1l3-WGA小鼠的颅感觉神经节中，通过源自舌后部酸味味觉细胞的WGA分布来观察酸味神经通路，对血清素受体基因进行ISH与小麦胚芽凝集素（WGA）的双荧光标记分析，结果显示WGA阳性的颅感觉神经元很少表达任何一种血清素受体基因。这些结果表明，颅感觉神经元中表达的血清素受体不作为酸味味觉细胞的神经递质受体发挥任何作用。
