Intercellular signaling in frog taste buds: taste cells and basal cells

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There is morphological evidence for synaptic interactions between taste cells and basal cells in vertebrate taste buds. However, very little is known about a role of basal cells in the processing of gustatory signals. Membrane properties of cells at the basal region of a taste disk were investigated in this study. Firstly, we found that the apical membrane receptor sites are responsible for the taste responses of the frog glossopharyngeal nerve to electrolytes. This implies that small molecules like Naions do not use paracellular pathways. Therefore, excitation of basal cells would be elicited only by that of taste receptor cells. Secondanly, we investigated the membrane properties of cells by applying the patch-clamp technique to cells isolated from frog taste organ. Some of isolated rod cells and wing cells possess the two processes to the apical and to the basal region. Voltage-gated NaィイD1+ィエD1 inward currents and KィイD1+ィエD1outward currents were recorded in both rod cells and wing … More cells. The patch-clamp technique was also applied to 25 cells at the basal region of ataste organ in a slice of lingual epithelium. Ratios, voltage-gated NaィイD1+ィエD1 inward current/ KィイD1+ィエD1 outward current, varied with each cell. Only KィイD1+ィエD1 outward current (lack of NaィイD1+ィエD1 inward current) and large NaィイD1+ィエD1 inward current/small K+ outward current were seen in 6 cells (mean ratio ± SE, 0.17 ± 0.05) and 5 cells (12.97 ± 0.4.77), respectively. Other 14 cells exhibited large NaィイD1+]ィエD1 inward current/large KィイD1+ィエD1 outward current (1.82 ± 0.19). It appears that there are different types of cells at the basal region of taste organ. Among 9 cells at the basal region, application of 100 μM 5-HT to the Ringer solution led to an increase of input membrane resistance in 3 cells and a decrease in 2 cells. Since basal cells like Merkel cells contain 5-HT, the changes in input membrane resistance by 5-HT suggest that basal cells may modulate gustatory signals at the basal region of taste organ. Less