Transection of the glossopharyngeal nerve reduces energy and sugar intake but does not affect fat intake or meal patterns in rats offered a palatable cafeteria diet

Taste information is transmitted to the brain via branches of cranial nerves VII (chorda tympani, CT, and greater superficial petrosal, GSP), IX (glossopharyngeal, GL), and X (superior laryngeal branch of the vagus) with each nerve innervating relatively segregated fields of taste buds on the tongue, palate, and laryngeal epithelium. Approximately 70% of taste buds reside on the tongue and are innervated by the CT or GL. Previously we found that rats offered a 5-choice cafeteria diet after combined transection of the CT and GL (2NX) ate more fat, less sugar, and larger, but fewer meals each day resulting in no net change in total daily energy intake and suggesting a role for the CT and/or GL in food choice, regulation of macronutrient intake, and satiation signaling, but the role of the individual nerves was unclear. To begin identifying the role of each nerve, this experiment aimed to interrogate the effects of transection of the GL (GLX) on food choice and meal patterns in rats offered a cafeteria diet after recovery from GLX or SHAM surgery. We found that GLX did not affect fat intake or meal patterns, but, compared with SHAM-operated controls, GLX rats had lower sugar intake, driven largely by a heightened preference for the food choice with low fat and low sugar content. These findings indicate that the GLX alone is not responsible for the elevated fat intake or meal size found in rats after 2NX, but could be solely responsible for noted reductions in sugar intake.