Short Title: Fat and Carbohydrate Preferences in Gustducin and Trpm5 Knockout Mice

Trpm5 and -gustducin are key to the transduction of tastes of sugars, amino acids and bitter compounds. This study investigated the role of these signaling proteins in the preference for fat, starch, and starch-derived polysaccharides (Polycose), using Trpm5 knockout (Trpm5 KO) and -gustducin knockout (Gust KO) mice. In initial two-bottle tests (24 h/day), Trpm5 KO mice showed no preference for soybean oil emulsions (0.313- 2.5%), Polycose solutions (0.5- 4%) or starch suspensions (0.5- 4%). Gust KO mice displayed an attenuated preference for Polycose, but their preference for soybean oil and starch was comparable to that of C57BL/6J wild-type mice (WT). Gust KO mice preferred starch to Polycose whereas WT mice had the opposite preference. Following extensive experience with soybean oil emulsions (Intralipid) and Polycose solutions, the Trpm5 KO mice developed preferences comparable to the WT mice, although their absolute intakes remained suppressed. Similarly, Gust KO mice developed a strong Polycose preference with experience but they continued to consume less than WT mice. These results implicate -gustducin and Trpm5 as mediators of polysaccharide taste and Trpm5 in fat taste. The disruption in Polycose, but not starch preference, in Gust KO mice indicates that distinct sensory signaling pathways mediate the response to these carbohydrates,. The experience-induced rescue of fat and Polycos