Figure 5. Two-bottle taste preference test.

Preferences indicated are measured against water for sweet (1% sucrose), umami (150 mM monopotassium glutamate—MKG), bitter (100 μM quinine—25 μM quinine for Tas1r2,Tas1r3^(−/−)2 in a) or sour (10 mM citric acid) with or without 124 μM steviol or SG supplemented to the drinking solution. (a) The bar graphs show either the preference (up bars) or avoidance (down bars) for the indicated compound in a two-bottle preference test during 48 h. There is clear preference for stevioside (P=2 × 10⁻²⁶, n=48 mice over four different experiments) and rebaudioside A (P=2 × 10⁻²¹, n=24) in WT animals, and indifference to steviol (P=0.24, n=24, one sample t-test versus 0.5). Steviol increases the perception of sweet (P=0.037), umami (P=0.001) and bitter (P=0.003, n=24, paired t-test) solution in WT animals, but not in Trpm5^−/− mice. In Tas1r2,Tas1r3^(−/−)2 mice bitter taste is potentiated by steviol (P=0.018) and stevioside (P=0.048, n=24, paired t-test). The indicated significances show a difference between the taste compound and the taste compound together with steviol. (b) Initial taste preference presented as normalized cumulative lick count for water versus water without (left) or with steviol (right) over 5 min after 23 h of water deprivation of 14 and 7 WT mice, respectively. (c) As b with sucrose, (d) MKG and (e) quinine. (b–e) Details from Supplementary Fig. 7a,b,e–j. (f) Preference from b–e represented as average±s.e.m. of relative lick count between mice for the bottle containing the tastant without or with steviol. Two-sample t-test (steviol/MKG) or paired sample t-test (sucrose/quinine). (g) Individual preferences from the data in f, indicating the variation between mice. The boxplot gives the 25–75% data interval with the mean indicated as a square and the median as a line. See also Supplementary Figs 6–9. Citr. A, citric acid; NS, not significant; Quin., quinine; Stev., stevioside; Sucr., sucrose.