Disruption of the acquisition of a conditioned taste aversion by the N-methyl-D-aspartate antagonist MK-801

This study evaluated the effect of an NMDA receptor antagonist on learning of a novel taste aversion. Forty-one male, experimentally naive Sprague-Dawley rats were randomly assigned to one of three treatment groups: Saline/Saline (n = 8), Saline/LiCl (n = 21), or MK-801/LiCl (n = 12). On Day 1, the subjects were water deprived for 24 hrs. On Days 2 and 3 they were given two calibrated bottles of water to drink for 60 min. On Day 4, the animals were pretreated with either saline or MK-801, 30 min prior to exposure to the water and 5% sucrose solution. After 60 min, the bottles were removed, and the animals were immediately injected with either saline or LiCl. On Day 5 of the experiment, the subjects were given a two-bottle choice test with the water and sucrose and allowed to drink for 30 min. The MK-801/LiCl animals consumed significantly more sucrose than the Saline-LiCl animals, suggesting that MK-801 impaired learning of the aversion to the novel taste. These results support the notion that the NMDA receptor is involved in conditioned taste aversion.