The Role of the Chorda Tympani Nerve in the Gustatory Detection of Free Fatty Acids

Both the World Health Organization and the International Obesity Task Force have classified the prevalence of obesity as a global epidemic. The primary causes of obesity are sedentary lifestyles and high-fat diets. Such diets are preferred due to their high palatability. Fats are broken down into free fatty acids, such as linoleic and oleic acids. In order to determine the neural pathway responsible for transducing these free fatty acids, the chorda tympani nerve was examined. In this study, a conditioned taste aversion to linoleic and oleic acid was measured following chorda tympani nerve avulsion as demonstrated in a taste-salient assay by means of the Davis Rig. Animals formed conditioned taste aversion to linoleic acid at concentrations exceeding 44 μM. After cutting the chorda tympani nerve, rats no longer avoided linoleic acid. No taste aversion to oleic acid was detected; therefore, a stimulus generalization between linoleic and oleic acids did not exist. A second experiment was conducted with intact chorda tympani nerve animals, which demonstrated an active avoidance to NaCl. This study shows that rats are able to detect fat. Furthermore, the chorda tympani nerve is responsible for relaying taste information to the brain. It is understood that this animal model is applicable to humans. Therefore, in the future, this taste research could be useful in formulating dietary foods that are more palatable without high fat content.