Abstract
It is proposed that amiliride-sensitive epithelial Na+ channels (ENaCs) are involved in taste signal transduction for Na+ salts. Previous studies in C57 BL mice demonstrated that responses to NaCl are inhibited by amiloride in the choda tympani (CT) nerve but not in the glossopharyngeal (IXth) nerve, suggesting lack of amiloride sensitivity (AS) in the posterior tongue innervated by the IXth nerve. The AS also differs among inbred mouse strains. BALB mice showed very weak AS even in the anterior tongue. In this study, by using in situ hybridization and semiquantitative RT-PCR techniques, we examined expression of three subunits (α,β,γ) of ENaC in the fungiform papillae (FP), circumvallate papilla (CP) and tongue epithelial tissue without taste papillae (ET) in C57BL mice before and after CT nerve crush. The results demonstrated that, in intact mice, signals for α subunit were clearly detected in some spindle-shape cells in both FP and CP, whereas those for β and γsubunits were detected in FP, but only slightly in CP. After nerve crush, signals for three subunits in FP were observed in a few taste cells at 2 weeks and clearly detected at 4 weeks. These results together with those reported by previous studies suggest that expression patterns for the three subunits may contribute to AS and the tongue regional difference in AS. With regard to the strain difference in AS, we are examining the gene polymorphism for each subunits of ENaC in C57BL and BALB strains. [Jpn J Physiol 54 Suppl:S176 (2004)]
