抄録
Taste signals are transmitted from taste cells to gustatory nerve fibers through chemical synapses. Taste cells are morphologically classified into four types: I, II, III and basal cells. Among them, chemical synapses are observed only in type III cells with putative sour receptors. However, sweet, bitter and umami receptors are expressed in type II cells, and the mechanisms have not been elucidated. Recent reports have highlighted the role of ATP as a key neurotransmitter. Here we tried to detect ATP release from single taste cells with action potentials in mouse fungiform papillae. The action potentials were recorded with the electrode basolaterally attached to a cell. When an increase in the firing rate was observed in response to a tastant, the electrode solution was applied for luciferase assay to determine the ATP. Type II and III cells express gustducin and glutamic acid decarboxylase (GAD67), respectively. We identified these cell types with transgenic mice expressing GFP in gustducin- or GAD67-positive cells. When Type II cells responded to saccharin or quinine, ATP was detected in a firing rate-dependent manner. When Type III cells increased the firing rate by application of HCl, ATP was below the detection limit. The results suggest that the amount of ATP released from taste cells differ with the response properties, or that type III cells release another neurotransmitter. [J Physiol Sci. 2008;58 Suppl:S167]
