Concentration and state dependent reductions in corn oil intakes after glossopharyngeal nerve transections in rats

Previous studies indicate a role for the glossopharyngeal nerve (GL) in the detection of dietary fats. The present experiments examined the effects of bilateral glossopharyngeal nerve transections (GLx) on the intake of low (4.8%), moderate (16%), and full-fat (100%) corn oil in non-deprived, food-deprived, and water-deprived rats. The rats had access to oils, 0.3 M sucrose, and water in a gustometer that measured number of licks and latency to the first lick during brief access trials. The behavioral measures were used as indices of the amount consumed and the motivation to ingest, respectively. After baseline intakes had stabilized, the rats received GLx or sham transections (Sham) and were then re-tested. Pre and post-surgery responses were compared to determine the impact of GLx on intake and the motivation to ingest. In non-deprived rats, GLx reduced the intake of 4.8% and 16% oils and decreased the motivation to ingest these oils. In food-deprived rats, GLx prevented increases in the ingestion of 4.8% and 16% oils and in the motivation to ingest these oils. In water-deprived rats, GLx reduced the intake of 100% oil and produced a general decrease in the motivation to consume low, moderate, and full-fat emulsions. These results indicate that GL is partially involved in corn oil intake and suggest an interactive effect of oil concentration with homeostatic state.