Contribution of chorda tympani and glossopharyngeal nerves to taste preferences of rat for amino acids and NaCl.

To learn how the gustatory nerves convey information about the nutritionally dependent taste preference, intake of amino acid solutions and saline in rats with bilateral chorda tympani (CTX) and/or glossopharyngeal neurotomy (GPX) was determined during the feeding of a control diet (C) and a L-lysine (Lys) deficient diet (LD). Intact rats preferred L-arginine (Arg) more in C and Lys more in LD. The CTX group did not select nor ingest Lys in LD, and its intake of Arg was also low in C. The GPX group did not substantially alter its preference under both diets, while it did show an increase in total liquid intake. The preference changes in the CTX + GPX group appeared as combined effects of the CTX and the GPX groups. In an additional study, the preference for Lys shifted to higher concentrations and the total consumption of Lys increased in LD. The present data suggest that the chorda tympani nerves possibly function as discriminators of the nutritional information by altering the taste preference, and that the glossopharyngeal nerves may convey other functional taste information, such as aversive tastes, and sensory aspects of osmotic regulation. In addition, it is revealed that the animals have ability to search for a nutrient deficient in their body, and to ingest it to a level that at least nullifies the deficiency.