The sense of taste provides animals with valuable information about the nature and quality of food. When animal experience a bitter taste this is a warning against the ingestion of toxic and noxious substances. . The mechanism of this is through bitter taste receptors called T2Rs.The T2Rs are a family of approximately 30 different G-protein-coupled receptors (GPCRs) that are selectively expressed in the tongue and palate epithelium. Differences in T2Rs between species (human and mouse) can determine the selectivity of bitter taste responses. ( Mueller et al Nature 2005, 10th March vol 434 pp 225-9
Mice and humans have distinctive differences in their sensitivities to many bitter compounds
In mice (m)T2R5 is a high affinity receptor for cycloheximide (Cyx)
In humans (h)T2R16 is a receptor for (3-glucopyranosides (salicin and related compounds),
( h)T2R14 is a candidate receptor for picrotoxinin
(h)T2R44 and (h)T2R61/hT2R43 are receptors for denatonium, aristolochic acid and 6-nitrosaccharin
Several β-glucopyrano-sides evoke strong bitter taste in humans, yet mice are largely indifferent to these compounds
. Similarly, phenylthiocarbamide (PTQ, a well known bitter taste often used in human genetic studies, is ineffective in mice.
Mueller et al were able to confer human bitter taste responses on mice by introduction of human taste receptors.
.From Mueller et al Nature 2005, 10th March vol 434 pp 225-9

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