Chemical Senses Advance Access originally published online on July 19, 2005
Chemical Senses 2005 30(6):531-538; doi:10.1093/chemse/bji046
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Expression of Amiloride-sensitive Epithelial Sodium Channels in Mouse Taste Cells after Chorda Tympani Nerve Crush
1 Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan and 2 Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Correspondence to be sent to: Yuzo Ninomiya, Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. e-mail: nino{at}dent.kyushu-u.ac.jp
Our previous electrophysiological study demonstrated that amiloride-sensitive (AS) and -insensitive (AI) components of NaCl responses recovered differentially after the mouse chorda tympani (CT) was crushed. AI responses reappeared earlier (at 3 weeks after the nerve crush) than did AS ones (at 4 weeks). This and other results suggested that two salt-responsive systems were differentially and independently reformed after nerve crush. To investigate the molecular mechanisms of formation of the salt responsive systems, we examined expression patterns of three subunits (
, ß and 
) of the amiloride-sensitive epithelial Na+ channel (ENaC) in mouse taste cells after CT nerve crush by using in situ hybridization (ISH) analysis. The results showed that all three ENaC subunits, as well as -gustducin, a marker of differentiated taste cells, were expressed in a subset of taste bud cells from an early stage (1–2 weeks) after nerve crush, although these taste buds were smaller and fewer in number than for control mice. At 3 weeks, the mean number of each ENaC subunit and -gustducin mRNA-positive cells per taste bud reached the control level. Also, the size of taste buds became similar to those of the control mice at this time. Our previous electrophysiological study demonstrated that at 2 weeks no significant response of the nerve to chemical stimuli was observed. Thus ENaC subunits appear to be expressed prior to the reappearance of AI and AS neural responses after CT nerve crush. These results support the view that differentiation of taste cells into AS or AI cells is initiated prior to synapse formation.
Key words: amiloride-sensitive epithelial sodium channel, in situ hybridization, nerve crush, taste bud
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