This project will reveal physiological mechanisms whereby mammals make diet choices. Understanding diet choice is essential to solving a wide array of problems, from habitat conservation to medical compliance and nutrition. Taste plays an integral role in diet choice because it conveys nutritional and safety information about the composition of foods. Sweet foods motivate intake, whereas bitter foods are often avoided. To increase intake of bitter vegetables into children’s diets, repeated exposure is a common and powerful method. It is thought that learning about the foods may be sufficient to increase intake. However, previous research by the principal investigator suggests that there may be a shift in the taste of these foods, because repeated exposure can alter production of salivary proteins that change how foods taste. This project will test whether the suite of salivary proteins produced by rats differs based on the specific type of bitter chemicals consumed, how the chemicals and proteins interact with receptors in the mouth versus digestive tract, and how diet-driven changes in salivary proteins act to alter acceptance of nontoxic, bitter foods. This work will be conducted, in part, in the context of a new university research course designed to train underrepresented students in behavioral neuroscience research techniques and will be used as part of a sensory systems and nutrition outreach program in local elementary and high schools.
This research project will test the hypothesis that diet-induced upregulation of salivary proteins (SPs) allows an animal to increase consumption of a sampled, harmless, bitter food, but does not generalize to dangerous toxins. Aim 1 will examine whether the dietary acceptance driven by SPs is specific to the inducing stimulus, by comparing the pattern of SP expression in groups of rats exposed to different classes of bitter plant secondary compounds (PSCs). These animals will complete taste tests for each class of PSC to determine if increased acceptance is generalizable to other, sometimes similar, but more toxic, bitter compounds. Aim 2 will determine if SPs act by altering the negative signals from receptors in the digestive tract. To isolate the effects of SPs on post-oral feedback, licking responses to saccharin solutions will be measured while rats receive intragastric infusions of bitter stimuli dissolved in donor saliva with or without SPs. It is hypothesized that the presence of SPs will block the reduction in licking induced by bitter chemicals under control conditions, by reducing the aversive post-oral input. Aim 3 will test whether indirect exposure to bitter compounds (i.e., in amniotic fluid and milk) is sufficient to alter SP expression in offspring. SP expression of mothers and offspring will be quantified after maternal diet experience with PSCs to test for vertical transmission of diet preference. This research will extend knowledge of taste physiology by identifying a physiological mechanism for experience-based alterations in diet acceptance. The research findings will have broader applications to the fields of foraging ecology and human nutrition. The project integrates education and outreach activities with the research, and will train two graduate and 15-20 undergraduate researchers.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
