Profound conditioned taste aversion induced by oral consumption of 2-deoxy- d-glucose

Abstract

In a previous experiment rats avidly avoided a solution of 2-deoxy-d-glucose in 0.2% saccharin (2-DG+S), drinking less than 1 mL over 3 days. The present study investigated taste avoidance and conditioned taste aversion (CTA) to orally presented 2-DG+S as well as CTA in response to i.p. injections of 2-DG. In Experiment 1, rats were given either a glucose/saccharin(G+S) solution or 2-DG+S for eight 30-s test periods. Four seconds into the first 30-s test, rats in the 2-DG+S group licked significantly less than rats in the G+S group, and licking almost totally ceased in the remaining seven tests. Overnight water intake was not different between the groups, but when offered a G+S solution, rats in the 2-DG+S group almost totally avoided the solution and still showed a significant aversion to G+S when retested 6 days later. In Experiment 2, rats were allowed to drink G+S, and were then injected i.p. with 500 mg 2-DG/kg, 500 mg d-glucose/kg body weight in 0.3 mL water, or with 0.3 mL saline. When tested with a G+S solution the next day, rats in the 2-DG group showed a highly significant avoidance, while rats in the glucose group were not different from those in the saline group. The results of the second experiment are consistent with earlier studies of CTA induced by i.p. injections of 2-DG. The present study indicates that small amounts of orally ingested 2-DG produce a CTA as strong or even stronger than that following injected 2-DG, most likely by inducing malaise. Whether the onset of malaise is fast enough to account for the rapid initial avoidance of this solution or a taste factor is also involved is not yet clear.