Dye-coupling in taste buds in the mudpuppy, Necturus maculosus.

Electrical coupling in taste buds and in non-taste lingual epithelium in the mudpuppy was examined by injecting cells with a fluorescent dye, Lucifer yellow. Lucifer yellow coupling has been shown to indicate the presence of electrical junctions between cells. Lucifer yellow-filled taste cells usually have an elongate shape. Cells were an average of 111 microns long and were 13 microns in diameter at the widest region (nucleus). In taste buds, from a sample of 105 impalements we detected Lucifer yellow coupling in 21 cases: dye-coupled pairs of cells were observed in 17 cases, and trios of cells in 4 cases. Larger subsets of coupled cells (greater than 3) were not observed. Dye-coupled cells were usually equally intensely stained. In non-taste epithelium, we examined dye-coupling in the superficial and basal layers. Extensive Lucifer yellow coupling was found in the basal layer (15/15 cases). The number of cells coupled to the dye-injected cell varied from 3 to 5. In the superficial epithelium, dye-coupling was rare (1/45 cases). No dye-coupling was observed between epithelial cells and taste cells at the taste pore region. We conclude that strong electrical coupling in groups of 2-3 cells occurs in the mudpuppy taste buds. Coupling may occur selectively between identical types of taste cells (dark, light, etc.), but this remains to be determined. Electrical coupling also exists among basal epithelial cells but not in the superficial epithelial layers.