Chemical Senses Advance Access originally published online on May 24, 2006
Chemical Senses 2006 31(6):565-572; doi:10.1093/chemse/bjj061
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Amiloride Inhibition on NaCl Responses of the Chorda Tympani Nerve in Two 129 Substrains of Mice, 129P3/J and 129X1/SvJ
Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
Correspondence to be sent to: Yuzo Ninomiya, Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. e-mail: nino{at}dent.kyushu-u.ac.jp
Amiloride, a sodium channel blocker, is known to suppress NaCl responses of the chorda tympani (CT) nerve in various mammalian species. In mice, the NaCl suppressing effect of amiloride is reported to differ among strains. In C57BL mice, amiloride inhibits NaCl responses to about 50% of control, whereas no such clear suppression was evident in prior studies with 129 mice. However, evidence from behavioral studies is not entirely consistent with this. Recently, it has been found that genetic backgrounds of 129 mice differ within substrains. 129X1/SvJ (formerly 129/SvJ) mice differ from the 129P3/J (formerly 129/J) strain by 25% of sequence length polymorphisms. Therefore, we examined possible substrain difference between 129P3/J and 129X1/SvJ mice in the amiloride sensitivity of electrophysiologically recorded NaCl responses. Amiloride significantly suppressed CT responses to NaCl without affecting responses to KCl both in 129P3/J and 129X1/SvJ mice. However, the magnitude of the amiloride inhibition was significantly larger (
50% of control in response to 0.01–1.0 M NaCl by 100 µM amiloride) in 129X1/SvJ than in 129P3/J mice (20% of control in response to 0.03–0.3 M NaCl by 100 µM amiloride). Threshold amiloride concentration for suppression of responses to 0.3 M NaCl was 30 µM in 129P3/J mice, which was higher than that in 129X1/SvJ mice (10 µM). In 129X1/SvJ mice, the threshold amiloride concentration eliciting inhibition of NaCl responses and the magnitude of the inhibition were comparable with those in C57BL/6 mice. These results suggest that amiloride sensitivity of NaCl responses differs even among the 129 substrains, 129P3/J and 129 X1/SvJ, and the substrain difference of 129 mice in amiloride sensitivity is as large as that between two inbred strains (129P3/J and C57BL/6).
Key words: amiloride, chorda tympani nerve, mouse substrain difference, salt taste
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  N. Shigemura, T. Ohkuri, C. Sadamitsu, K. Yasumatsu, R. Yoshida, G. K. Beauchamp, A. A. Bachmanov, and Y. Ninomiya Amiloride-sensitive NaCl taste responses are associated with genetic variation of ENaC {alpha}-subunit in mice Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2008; 294(1): R66 - R75. [Abstract] [Full Text] [PDF]
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