Perinatal Administration of a Bitter Tastant Influences Gene Expression in Chicken Palate and Duodenum Shira L. Cheled-Shoval, †,‡ Maik Behrens, § Wolfgang Meyerhof, § Masha Y. Niv, ‡ and Zehava Uni* ,† † Department of Animal Science and ‡ Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food, and Environment, and The Fritz Haber Center for Molecular Dynamics, The Hebrew University, Rehovot 76100, Israel § Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, 14558 Nuthetal, Germany ABSTRACT: Bitter taste receptors (Tas2rs) and downstream effectors are responsible for mediating bitterness perception and regulation of food choice in mammals. Using RT-PCR, we demonstrated the expression of three Tas2rs and taste signal transduction molecules, α-gustducin, PLCβ2, and TRPM5, in the palate, tongue, and gastrointestinal tract sections in chicken. The bitter tastant quinine activates all three chicken Tas2rs in vitro as shown using calcium-imaging assays of transfected cells. Administration of quinine postnatally or perinatally (both pre- and posthatch) to chickens increased the expression of Tas2r genes in the palate by 6.45-fold (ggTas2r1 postnatal treatment), 4.86-fold (ggTas2r1 perinatal treatment), and 4.48-fold (ggTas2r7 postnatal treatment) compared to the genes’ expression in the naı ̈ ve group respectively, and affected taste related gene expression in the duodenum. Whereas no-choice intake of quinine solution was not significantly lower than that of water in naı ̈ ve chicks, the treatment groups postnatal, prenatal, and perinatal showed significantly lower intake of quinine by 56.1, 47.7, and 50.2%, respectively, suggesting a possible trend toward sensitization. These results open new venues toward unraveling the formative stages shaping food intake and nutrition in chicken. KEYWORDS: bitter taste receptors, taste tests, quinine, gene expression, chicken ■ INTRODUCTION Basic taste modalities are crucial determinants for food choice and intake. 1 Bitter and sour indicate potentially poisonous or spoiled food, and salty signals the presence of electrolytes, whereas sweet and umami indicate nutritious food. Bitterness is usually believed to guard against toxicity, but some nutritious feedstuffs from plants contain bitter compounds that cause an aversive reaction without being poisonous at physiological concentrations. 2-4 Today, the high cost of feed in animal production has led to an attempt to include alternative grains and feedstuffs, such as byproducts from human food processing and biofuel production. 5,6 Therefore, a critical question in animal nutrition is how mechanisms governing bitter taste perception interact with intake behavior. Bitter taste perception in vertebrates is mediated through various members of the G-protein-coupled receptor subfamily called the taste 2 receptor family (Tas2rs) and their downstream effectors, 7 expressed by a specific subset of taste receptor cells found in the oral cavity. 8,9 In the bitter taste signaling cascade, a tastant binds to the Tas2r, causing a conformational change, dissociation of the heterotrimeric G- protein subunit (α and βγ), activation of phospholipase Cβ2 (PLCβ2), Ca 2+ release from intracellular Ca 2+ stores, opening of transient receptor potential melastatin 5 (TRPM5) channels, Na + influx, and cell depolarization (reviewed in ref 10). Taste-bud development occurs prenatally in chicken and is completed by embryonic day 19 (E19). 11 Whereas humans and rodents have ∼25-35 Tas2r genes, 12,13 chickens only have three. 14 Despite this relatively low number of Gallus gallus (gg) Tas2rs, chickens show dose-dependent and strain-dependent aversion and other behavioral responses to bitter taste stimuli. 15,16 The clear and rapid behavioral responses to bitter taste stimuli, even in prenatal periods, including prolonged head shaking and beak clapping episodes, significant aversion, and decreased tastant intake, make them highly suitable as a model for behavioral taste experiments. 17-19 In addition to orally expressed Tas2rs, extra-oral gastro- intestinal tract (GIT) expression of Tas2rs and downstream effectors has been demonstrated. 20,21 These recent findings raise questions about the roles of taste transduction pathways in extra-oral tissues such as the GIT and emphasize the importance of understanding tastants’ effects on these tissues. The aim of the current study is to explore the expression of bitter taste transduction machinery in poultry gustatory and extra-gustatory tissues. The bitter tastant quinine elicits aversive responses in chicken and many other species. 15,17,22,23 Following Behrens et al. ’ s survey of chicken tastants repertoire, 24 we illustrated quinine’s ability to activate all three chicken Tas2rs in vitro using calcium-imaging assays of transfected cells. We then administered quinine to chickens prenatally, postnatally, or twice perinatally (before and after hatch). Gene expression of ggTas2rs and downstream signaling genes was analyzed using real-time PCR, and behavioral intake tests were performed. Received: May 13, 2014 Revised: November 23, 2014 Accepted: November 26, 2014 Article pubs.acs.org/JAFC © XXXX American Chemical Society A dx.doi.org/10.1021/jf502219a | J. Agric. Food Chem. XXXX, XXX, XXX-XXX