Fig. 5.
Taste-salient brief-access tests of quinine responsiveness of mice bearing short-term conditional loss of RGS21 expression. (A) Schematic representation of timing of pre- and post-tamoxifen brief-access tests for quinine (“aversive stimulus”; Table (i)) performed with 8-week-old (postnatal [P] day 56) conditional Rgs21 knockout mice (Rgs21fl/fl;CAGGCre-ER). (B) To demonstrate the degree of Rgs21 expression loss achieved by tamoxifen treatment, Rgs21fl/fl;CAGGCre-ER mice were IP injected once a day for five consecutive days, either with 75 mg/kg of tamoxifen or corn oil (vehicle only). Seven days after the final injection, tongues were excised and RNA was isolated for qRT-PCR analysis of Rgs21 mRNA expression (normalized to 18S rRNA levels) in CV papillae (panel B; n = 4 per treatment group; unpaired Student t test, P = 0.007). (C) Twelve individual mice, homozygous for the loxP site-flanked exon 5 allele of Rgs21 (Rgs21fl/fl) and heterozygous for the ubiquitiously expressed, tamoxifen-inducible Cre recombinase transgene (CAGGCre-ER), were profiled for quinine responsiveness in brief-access tests performed before (“pre-injections”) and 1 week after five daily intraperitoneal injections of 75 mg/kg tamoxifen to induce Rgs21 exon 5 excision. Repeated-measures ANOVA with Sidak posthoc testing was performed to establish significance of intra-animal changes pre- vs post-tamoxifen in aversion to indicated quinine sulfate concentration (n = 12; ns, not significant [P >> 0.05]; ****, P < 0.0001).