Abstract
It is known that there exist two different response components of the CT nerve for sweeteners in mice, one is inhibited by gurmarin [gurmarin-sensitive (GS)] and the other is not [gurmarin-insensitive (GI)]. The C57BL strain possesses both components in the taste buds innervated by the CT nerve, whereas BALB mice almost exclusively have the GI component. Recently, it has been found that TRPM5 is a highly temperature-sensitive, heat-activated channel, and increasing temperature between 15 and 35°C markedly enhances the CT nerve responses to sweeteners in wild-type but not in TRPM5 knockout mice. In the current study, therefore, we examined the temperature dependency of GS and GI sweet taste responses of the CT nerve in C57BL/6N and BALB/c mice. In both mice, the CT nerve responses to all sweeteners before and after lingual treatment with gurmarin increased significantly on increasing the temperature from 15 to 35°C. Comparing the GS and GI components, we found that increase of response of the GS component was smaller than that of the GI component at the higher temperature range (increasing temperature from 25 to 35°C). In addition, responses to non-caloric sweeteners were larger in the GS than the GI component, whereas the reverse was true for sugars responses. These results suggest that 1) both GS and GI components exhibit the temperature sensitivity, and 2) the temperature sensitivity of sweet responses differs between GS and GI components, and 3) response of GS and GI components differs among sweet compounds. [J Physiol Sci. 2007;57 Suppl:S102]
