Induction of salivary proteins modifies measures of both orosensory and postingestive feedback during exposure to a tannic acid diet

There are hundreds of proteins in saliva. Although it has long been hypothesized that these proteins modulate taste by interacting with taste receptors or taste stimuli, the functional impact of these proteins on feeding remains relatively unexplored. We have developed a new technique for saliva collection that does not interfere with daily behavioral testing and allows us to explore the relationship between feeding behavior and salivary protein expression. First, we monitored the alterations in salivary protein expression while simultaneously monitoring the animals' feeding behavior and meal patterns on a custom control diet or on the same diet mixed with 3% tannic acid. We demonstrated that six protein bands increased in density with dietary tannic acid exposure. Several of these bands were significantly correlated with behaviors thought to represent both orosensory and postingestive signaling. In a follow-up experiment, unconditioned licking to 0.01-3% tannic acid solutions was measured during a brief-access taste test before and after exposure to the tannic acid diet. In this experiment, rats with salivary proteins upregulated found the tannin solution less aversive (i.e., licked more) than those in the control condition. These data suggest a role for salivary proteins in mediating changes in both orosensory and postingestive feedback.