AN ANALYSIS OF SYNAPTIC TRANSMISSION MECHANISM FROM TASTE RECEPTOR CELL TO GUSTATORY NERVE

点击翻译按钮获取中文摘要

Immunohistochemical studies have demonstrated that taste receptor cells containing serotonin exist in taste buds. In the previous studies, we detected serotonin secreted from the serosal side of the lingual epithelium in response to the repeated application of NaCl or citric acid to the mucosal side of the lingual epithelium using full-automatical perfusion/sampling device for epithelial tissue and HPLC. Therefore, we attempted to detect serotonin secreted from a single taste bud in response to the application of taste stimuli to the taste pore using localized stimulation procedure and carbon fiber electrodes. However, we were unable to detect any monoamines. We attempted to immunohistochemically detect localization of several subtypes of glutamatergic receptor molecules in the taste buds of the fungiform papilla. One of the metabotropic glutamatergic receptors, mGluR4 was detected in the taste bud cells, but not in the gustatory nerve terminal of the afferent synapse. Taken together w … More ith electrophysiological data, mGluR4 in the taste bud cells possibly play an inhibitory role for transduction mechanism of umami. These results suggest mat substances other than glutamate and monoamines mediate the transmission from taste receptor cells to gustatory nerves. Therefore, we performed a bioassay using vallate papilla (VP)/von Ebner's gland (VEG) complex, where several receptor molecules are expressed on the acinar cells. The results indicated that localized bitter stimuli to the cleft of isolated vallate papilla suppressed voltage-gated K^+ currents of acinar cells, whereas sour stimuli induced inward current responses in acinar cells with slow time course, suggesting that these actions of taste stimuli are due to paracrine effect of transmitters released from taste bud cells. These findings also suggest that transmitter released by bitter stimulus is different from that by sour stimulus, and receptor molecules for these multiple transmitters were expressed on acinar cells of VEG. Less