Fig. 3.
Only bi-allelic ablation of Rgs21 expression blunts aversion to the bitterant quinine and blunts preference for low concentrations of NaCl salt. (A) Schematic representation of timing of two-bottle choice tests performed with 8-week-old (postnatal [P] day 56) constitutive Rgs21 knockout mice (Rgs21Δ5/Δ5) and littermate controls (wild-type Rgs21+/+ and heterozygous Rgs21+/Δ5 F1 progeny). (B, C) Tests of two-bottle choice for an ascending concentration series of the bitterant quinine sulfate (B) or the salt NaCl (C) versus unadulterated drinking water were performed with heterozygous Rgs21+/Δ5 F1 progeny (n = 6) alongside Rgs21+/+ (n = 11) and Rgs21Δ5/Δ5 (n = 10) littermates. A preference ratio of 0.5 (dashed line) indicates indifference towards the tastant solution relative to water. Each test was assessed with a two-way ANOVA and differences between the groups in preference or aversion to specific concentrations of tastant solution were determined using Sidak posthoc test to correct for multiple comparisons (*, P < 0.05; **, P < 0.01, ***, P < 0.001, ****, P < 0.0001; ns, not significant [P >> 0.05]). Wild-type and Rgs21+/Δ5 mice appeared to have no difference in preference at any concentration tested. Inset bar graph of panel B, Data from qRT-PCR (SYBR Green detection) of the Rgs21 mRNA transcript, which is seen to be completely absent in Rgs21Δ5/Δ5 mice, but equally detected in tongue tissue from both Rgs21+/+ and Rgs21+/Δ5 mice. Inset bar graph of panel C, Data from two-bottle choice testing for an ascending concentration series of the sour tastant hydrochloric acid (HCl), indicating no significant difference in aversion at the 10 mM or 30 mM concentrations between the two indicated genotypes (n = 7 for both groups).